Survival Weapons: The AR-15 Family Of Weapons

 

Source: "The Sporting AR: Ideal for Hunting?"--Gun Digest. Note the polymer MagPul butt-stock, back up iron sight (BUIS), handguard, and magazine.

    Although the Armalite Rifle Model 15 (AR-15) family of weapons traces its roots back to the development of what would become the M-16 rifles and, later, M-4 carbines adopted by the military, the modularity of the platform combined with its popularity among the shooting public has resulted in a highly diverse family of civilian small arms that run the gambit from short barreled pistols up to target and hunting weapons with barrels in excess of 20-inches, and in a multitude of calibers. And, perhaps more than any other weapon--or family of weapons--myths have grown up around the AR, as the weapon family is often called, and among its detractors it swings between being nothing more than an underpowered poodle-shooter to a "weapon of war" that by its seeming appearance is the deadliest small arm devised by humankind. What is undeniable is its popularity, such that I sometimes joke that in the future all rifles will be ARs, AKs, or some hybrid of the two.

    Whole books have been written about the AR, its history, variants, parts, maintenance, use, and so on. I cannot and will not try to replicate that here. Rather, my intent is to give a brief overview of the platform and what it offers in the context of prepping and survivalist planning.

Military ARs over the years. From top to bottom: M16A1, M16A2, M4A1, M16A4 (Source). Note the detachable carry handle/rear sight on the M16A4.

General Description:

    For the general information as to weight and size, I will primarily rely on military versions of the weapons since there is so much variance between the different models and types available on the civilian market. Obviously the military weapons are select fire--capable of automatic or burst fire--while civilian weapons are not; but the military variants should provide good points of comparison or reference as to size and weight.

M16A1 (Source: "Special Ops Photographers Offer Unfiltered Look at 'Faces of War'"--WTTW)

M16A1: This is the Vietnam era rifle sporting a thin (pencil-profile) barrel and fixed carrying handle and rear sight. If your light-weight AR rifle can match this in weight, you are doing very well.

Cartridge:  5.56 x 45mm (55 grain projectile)

Operation:  Gas operated, direct gas impingement with a rotating bolt.

Feed: 20 or 30-round detachable box magazine.

Weight (empty): 2.89 kg (6.37 lbs)

Length: 986 mm. (39 inches)

Barrel: 508 mm. (20 inches)

M16A2 (Source: Wikipedia). Note the different rear sight, front handguard, and differently shaped plunger for the forward assist, as well as the inclusion of a brass deflector behind the ejection port.

M16A2: This is the heavy barrel version with a fixed carry handle but upgraded sights and a different pistol grip, handguard, stock, and forward assist.

Cartridge:  5.56 x 45mm (62 grain projectile)

Operation:  Gas operated, direct gas impingement with a rotating bolt.

Feed: 30-round detachable box magazine.

Weight (empty): 3.77 kg (8.31 lbs)

Length: 1006 mm. (39.6 inches)

Barrel: 508 mm. (20 inches)

M4 Carbine (Source: "Army Finds Fix for Dangerous Glitch in M4 and M4A1 Service Rifles"--Military.com)

M4A1: This is the popular flat-top model featuring a Picatinny rail instead of a carrying handle.

Cartridge:  5.56 x 45mm (62 grain projectile)

Operation:  Gas operated, direct gas impingement with a rotating bolt.

Feed: 30-round detachable box magazine.

Weight (empty and without optics or other accessories): 3.01 kg (6.63 lbs)

Length: 838 mm (33 in) (stock extended); 756 mm (29.75 in) (stock retracted)

Barrel: 368 mm. (14.5 inches)

Mk 12 SPR (Source: Wikipedia)

Mk 12 Special Purpose Rifle

Cartridge:  5.56 x 45mm

Operation:  Gas operated, direct gas impingement with a rotating bolt.

Feed: 20 or 30-round detachable box magazine.

Weight (empty): 4.5 kg (10 lb) (fully loaded, w/heavy barrel added with a optic)

Length: 952.5 mm (37.5 inches)

Barrel: 457.2 mm (18 inches)

Source: "POTD: U.S. Marines in Infantry Marine Course"--The Firearm Blog. 
The Marine in this photograph appears to be using an M27 Infantry Automatic Rifle manufactured by Heckler & Koch and based on the HK416. With the scope, the M27 is designated by the Marines as the M38 Designated Marksman Rifle. Although the weapon's appearance is almost indistinguishable from the AR15, it uses a short stroke piston system rather than the direct impingement system in the AR.

    Below I have some civilian ARs (commonly called modern sporting rifles (MSRs)):

Ruger 556 Rifle

Ruger 556 Rifle (Model # 8515):

Cartridge:  5.56 x 45mm

Operation:  Gas operated, direct gas impingement with a rotating bolt.

Feed: Detachable box magazine.

Weight (empty): 6.5 lbs (2.95 kg)

Length: 32.25" - 35.50" (819 mm - 902 mm)

Barrel: 16.10" (409 mm)

DDM4® Hunter 300 Blackout (Kryptek Highlander)

Daniel Defense DDM4® Hunter 300 Blackout:

Cartridge:  .300 Blackout

Operation:  Gas operated, direct gas impingement with a rotating bolt.

Feed: Detachable box magazine.

Weight (empty): 6.55 lbs (2.97 kg)

Length: 32 1/4" – 35 7/8” (819 mm - 911 mm)

Barrel: 16" (406 mm)

Savage Arms MSR 10 Long Range

Savage Arms MSR 10 Long Range: This is an AR version commonly called an AR-10 pattern that is capable of shooting longer ammunition--in this case, .308/7.62x51mm. I realize that this is not technically an AR-15, but the modern AR-10 rifles probably have more in common with the AR-15 than to the original AR-10s, and are an offshoot of the AR-15's popularity.

Cartridge:  .308/7.62x51mm

Operation:  Gas operated, direct gas impingement with a rotating bolt.

Feed: Detachable box magazine.

Weight (empty): 9.75 lbs (4.42 kg)

Length: 40.63 - 42.63 inched (1016 mm)

Barrel: 20 inches (508 mm).

Springfield Armory Saint® Victor Ar-15 Pistol, B5

Springfield Armory Saint® Victor AR-15 Pistol, B5:

Cartridge:  5.56 x 45 mm

Operation:  Gas operated, direct gas impingement with a rotating bolt.

Feed: Detachable box magazine.

Weight (empty): 5 lbs 6 oz (2.44 kg)

Length: 23.75" - 28.25" (603 mm - 718 mm)

Barrel: 7.5" (190 mm)

    Hopefully this gives you an idea as to the size and weight of various AR weapons and configuration. Although the civilian weapons are cosmetically similar to the military weapons, capable of even using many of the same parts so long as the civilian weapons are "mil-spec" AR-15 (and not all civilian weapons are), the primary difference is that the military M16s and M4s are capable of full automatic or burst fire (firing 3 shots per pull of the trigger) and, therefore, suitable for serving the roll of an automatic rifle and laying down the suppressing fire necessary for modern fire and maneuver warfare.

Background:

    For most rifles, the history is a matter of academic curiosity. But the history of the AR-15 is so wrapped in the development of the ammunition and specific features and characteristics to solve real and imagined problems, that it behooves the prepper to learn from the research and practical experience that has lead to the modern AR weapon system.

    The AR very nearly didn't happen. But I think we would have wound up with something with similar weight, performance, and caliber because the AR was the product of a confluence of various factors including research on more lethal FMJ ammunition, better identification of the distances at which combat took place, the desire to reduce weight, and the need to maximize firepower at the level of the individual soldier.

    At the turn of the 19th to 20th Century, the majority of nations had settled on a high-power manually operated bolt action rifle as their standard infantry weapon employing a bullet of approximately .30 caliber (between .308 inches and .312 inches was typical), generally with a 5-round internal magazine filled by either a stripper or en bloc clip, and capable of engaging targets out to 1,000 yards or more. This shouldn't be taken to mean that the average soldier could sight on an individual target at that distance, but that companies of men would fire so that the bullets would fall on a beaten area at those distances, similar to how a machine gun might be employed today. But as World War I would demonstrate, the typical infantry rifle was grossly overpowered by way of the cartridge employed, but grossly deficient in its ability to project firepower. There was also dissatisfaction with the wounding capabilities of .30 caliber FMJ bullets.

    Bullet Lethality:

    There is a grave misunderstanding when it comes to bullet lethality. Most shooters are familiar with ammunition that is designed to expand upon striking a fleshy target because that is how the majority of self-defense and hunting loads are designed. A hunting round that is correctly matched to the size and skin thickness of the animal being hunted is designed to inflict a large amount of damage in order to humanely kill the animal in, hopefully, one shot. 

    There are various ways a bullet can be engineered to expand, but the most common is to leave the tip of the bullet open, exposing the lead core, so when it strikes an animal, the soft lead deforms and is pushed backward into the bullet, causing the metal jacket to open up so that the whole round ends up looking like a mushroom. Some more modern designs use a polymer tip designed to initiate the expansion. The expansion of the bullet also causes much of the energy from the bullet to transferred to the target causing significant damage from hydrostatic shock--essentially a shock wave moving through the liquid contained in the body--if the bullet is still moving at high speed. 

    The military, however, cannot use such bullets in combat. First, the Hague Convention of 1899 prohibits the use of bullets designed to expand. Although the United States is not a signatory, it still abides by the provisions of the agreement. Second, expanding bullets offer problems that preclude them from general military use independent of the Hague Convention: the exposed lead tips can become deformed either during cycling or during storage, leading to poor accuracy and/or cycling in the weapon. This is particularly true in an automatic weapon. Using bullets with a full metal jacket (FMJ) obviates such problems. And, third, FMJ ammunition is less expansive to manufacture, making it easier to stockpile large amounts.

    On the other hand, while FMJ is very suitable for the military as far as reliability and logistic issues, the larger caliber bullets in use through World War I, World War II, and Korea, were not as lethal as the military would like because the bullets did not expand or fragment, had minimal yaw and typically did not even deform much when striking an enemy. 

    As early as 1928, the U.S. Army found that a smaller caliber rifle bullet was deadlier than the larger, .30 caliber bullet that was in use. At that time, the Army tested the effectiveness of three different calibers (the .30-06, using a .308 caliber bullet; a .276 caliber bullet; and a .256 caliber bullet) by shooting swine. The results showed that at short range—i.e., 300 yards—the .256 gave “by far” the most severe wounds, with the .276 in second place. As the ranges approached 600 yards, the performance narrowed, with all three rounds performing about equal. Based on this testing, the Army very nearly adopted the .276 Pederson round, but decided the expense was too great to justify during the depths of the Great Depression while it still sat on large stockpiles of .30-06 remaining from World War I. 

    In the early 1950s, the Army again revisited the issue, and in March 1952, Donald L. Hall released his report "An Effectiveness Study Of The Infantry Rifle" (aka, the Hall Report). Hall determined that a theoretical .21 caliber bullet should be 2.5 times as lethal as the standard M2 ball ammo that was in use by the military, although its effectiveness would be at closer ranges. In that regard, Hall observed, based on data obtained from wound ballistic survey from the Korean War, that the mean distance at which hits were obtained by soldiers was 120 yards, and only 10% of hits were obtained at distances greater than 300 yards. He concluded, therefore, that a rifle that was more effective up to distances of 500 yards was more desirable than a rifle that was more effective at greater than 500 yards. This favored a lighter, high-velocity bullet over the .30-06 ammunition then in use. Hall also experimented with the .220 Swift, including specially built 60 grain .22 projectiles. Hall recommended that the Army conduct further study of small caliber, high velocity ammunition as a replacement for the heavier .30-06 ammunition then in use.

    Hall's research, as well as the results of other research and testing, was compiled and analyzed in a June 1952 report entitled "Operational Requirements For An Infantry Hand Weapon". This report again noted that based on actual battlefield reports and tests conducted by the Army, that the vast number of actual successful shots on target occurred at under 300 yards; and that at 500 yards, both standard infantrymen and marksmen were equally bad at actually being able to strike man-sized targets. This report also concluded that a low recoil, small caliber (i.e., less than .30), high velocity round with wounding characteristics equal or exceeding the M1 Garand out to 300 yards be considered.

    Engagement Ranges:

    Studies of battlefield engagements during World War II and the Korean War revealed that most small arms engagements occurred at ranges of 300 yards or less making much of the power of rounds such as the .30-06 superfluous. Importantly, if a rifle was not required to shoot a powerful long distance cartridge, the rifle (and ammunition) could be made lighter while still capable of controlled automatic fire. This was the thinking that led the Germans to field the Stg. 44 and the Soviets to introduce the AK-47 and AKM rifles. These three rifles kept the .32 or .31 caliber of their bolt-action predecessors (albeit at a reduced bullet weight) but in a shorter overall length of cartridge of reduced power with a useful battlefield range of 300 yards or so. Combined with stamped steel receivers in the case of the Stg. 44 and AKM, it also resulted in an overall lighter rifle.

    Firepower:

   Although the Russo-Japanese War of 1904 and 1905 amply demonstrated the importance of machine-guns, World War I finally impressed it into the minds of military leaders and soldiers alike. The challenge was how to get this firepower into the hands of the platoon, squad, or, even better, the individual soldier. 

    Initially, the belligerents efforts were focused on developing or obtaining light machine guns that could be issued at the platoon level. The United States, for instance, made use of the French-made Chauchat and M1909 Benét–Mercié light machine guns before developing and issuing the Browning Automatic Rifle (BAR), although the BAR was issued so late in the war that it saw only limited use. In World War II and Korea, however, the BAR would be widely used at the platoon or even squad level much like a light machine gun.

    But light machine guns--even less weightier variants such as the BAR--were still too heavy and expensive for general issue to troops. There was some research into lighter semi- or fully automatic rifles, but nothing substantive. Instead, the WWI belligerents began looking at weapons using pistol caliber ammunition: the Maschinenpistole in German (literally, machine pistol) but what the British and the United States would term submachine guns. Although pistol ammunition is greatly underpowered, the fact that these weapons employed much larger magazines compared to the infantry rifles, were compact, and could be used effectively when fired in full automatic mode made them invaluable to troops, particularly when raiding trenches in WWI, and in urban combat or fighting among the hedgerows of France in WWII. It is telling that countries that continued to use high power rifle rounds following World War II, also continued to field submachine guns or similar (e.g., the U.S. M2 carbine, the British Sterling, and so on).

    The first successful submachine gun adopted in any numbers was the German MP-18, which was introduced into service in 1918 as the primary weapon of the Sturmtruppen (literally, storm troopers), assault groups specialized in trench combat. In the 1920s and 1930s, submachine guns and true machine pistols would be further developed and play roles in the Spanish Civil War, the conflicts in China, and the other wars that were the fallout of World War I. By the time World War II came along, the Germans were heavily outfitted with improved submachine guns, including the infamous MP-38 and MP-40 "Schmeisser". The Soviets also relied heavily on the submachine guns for their shock troops, outfitting whole companies with the weapons. Britain was so desperate for submachine guns at the start of the war that it was purchasing them from whatever sources could be found, but eventually developed its inexpensive Sten submachine gun. Even the United States employed submachine guns in World War II and beyond--primarily a less expensive and easier produced version of the Thompson submachine gun and, subsequently, the M3 "Grease Gun". 

    But the United States had also pursued options other than the submachine gun. One such option, developed during World War I, was the Pederson Device. It employed a mechanism that replaced the standard bolt in a Springfield M1903 rifle with a device that turned the M1903 into a semi-automatic weapon firing from a 40-round box magazine and using a short .30 caliber cartridge that was about 1.5 times as powerful as a typical handgun cartridge. This device, it was believed, would allow troops the range and lethality of the more powerful .30-06 rounds when needed, but simply by removing the bolt and inserting the device, greater ammunition capacity and firepower for when assaulting enemy trenches. Unfortunately, the devices and modified rifles to use them were only just coming off the production line when the Armistice was signed.

    The next option, however, proved more successful and saw more widespread use: the adoption of the semi-automatic M1 Carbine (which were produced in greater numbers than the M1 Garand) and, in 1944, its gradual replacement with the select fire M2 Carbine. The M1 was intended as a weapon to be used by rear echelon troops and troops whose duties prevented them from carrying the larger M1 Garand rifle such as machine gun, mortar, or artillery crews, but being more powerful and effective than the 1911A1 .45 handgun. The M1 became popular even with frontline troops (particularly in the Pacific) because it was lightweight (just 5.2 lbs) and used a very manageable .30 cartridge that has been described as falling somewhere between a pistol and a rifle cartridge in power; it has roughly the same energy at 100 yards as the .357 Magnum has at the muzzle of a handgun. However, as soon as it was issued, troops started clamoring for a version that could be fired in an automatic mode. Thus, the development of the M2.

    The M2 saw limited use in the battle to capture Okinawa. "However, they saw wider-scale action five years later in the Korean War. There, the carbines allowed rear-area troops to quickly lay down heavy suppressive fire in response to ambushes by Communist infiltrators, who liked to sneak as close as possible to American lines to make effective use of their PPsH-41 ‘burp guns.' Because the M2 was capable of responding with automatic fire, it was also favored for leading night patrols, where combat would inevitably occur at short range." The M2 Carbine would continue to be used until the M16 replaced it.

    It was the Germans, however, that pointed the way to the future with the adoption of the Sturmgewehr 44 (Stg. 44)--literally "storm" or "assault rifle". This weapon employed a reduced power "intermediate" cartridge that gave it an effective range of 300 yards, but was still reasonably controllable in automatic mode to enable its use to provide suppressive fire. The Soviets followed suit with their own assault rifle: the AK47 and, later, AKM, likewise employing an intermediate cartridge.

    Other Trends:

    A couple other trends of note that presaged the development of the AR rifles were the quest for a lighter weapon, more easily manufactured weapon (most post-WWII rifles would use stamped sheet steel), and the desire for a weapon that could do it all--replacing the automatic rifle, standard infantry rifle, and submachine gun--using a single standard caliber.  

    Robert Conquest’s Third Law of Politics:

    By the mid-1950s, the trends and research pointed the way to the future rifle to replace the M1 Garand (as well as the BAR, M1 Carbine, and submachine gun). It would, above all, need to be able to provide automatic fire for suppressive purposes, firing from a detachable box magazine, with low enough recoil that the automatic fire could effectively be directed on target. It would also need to be light and handy enough that it could replace the submachine gun and M1 Carbine both on the front lines as well as for arming support and rear-echelon troops. Because research and experience showed that the vast majority of individual weapon fire resulting in hits occurred within 300 yards, and rarely more than 500 yards, a less powerful cartridge than the .30-06, .303 Enfield, German 7.92 mm, and Russian 7.62x54R could be employed and, in fact, had been successfully employed by the Germans in their Stg. 44. However, rather than an "intermediate" round like the German 7.92 Kurz, research on lethality concluded that a small caliber, high velocity round would be better in terms of weight and lethality. In other words, all the data and trends indicated that the rifle to replace the M1 Garand should be something with the general characteristics of the M16 and its .223 cartridge.

    With all that in mind and known by Army Ordinance, what rifle did they decide upon and produce? The M14--a weapon that was pretty much the complete opposite of what was needed. The M14 employed the .308/7.62 NATO rounds: essentially a .30-06 but with a shortened and slightly thicker case based off the .300 Savage that made it more suitable for use in automatic weapons. Because the weapon was firing such a powerful cartridge, it was necessarily heavy and largely uncontrollable in automatic fire. In fact, the majority of the M14s ultimately issued to troops came with no selector lever so they could only be used in semi-automatic. Because of the size of the weapon, it was far too large to be carried as a personal defense weapon for non-combat troops. And not wanting to adopt a foreign design, and so as to not have to replace its manufacturing machinery, the weapon was made as similar to the M1 Garand as possible. To top it off, the development of the M14 had been long and incredibly expensive, and the roll out was problematic at best.

  A 1963 article describes the fiasco thusly:

    After nearly 20 years of Pentagon bungling that has cost US taxpayers over $100 million so far, the Army is issuing our GIs a new automatic rifle that experts think is inferior to the gun we already have.

    The rifle is called the M14. It is slowly replacing the M1 Garand carried by millions of servicemen in World War II and Korea. The only trouble is it doesn’t work as well as the M1 and it’s much harder and more expensive to manufacture.

    If you haven’t heard about the M14 or its troubled history don’t be surprised. The Army has been rather quiet about it lately, and with good reason.

    The design, testing and production of the M14 were so badly botched that Defense Secretary MacNamera called the whole thing a ‘disgrace.’ And John C. Garand, inventor of the M-1 of which the M14 is a bastardized version – worries about what will happen when it’s used in combat. Reports from Vietnam indicate that Garand’s fears may well be justified.

    All told, the whole fantastic story of how the so-called ‘new’ Army rifle was developed is beginning to sound like one of the biggest snafus in U.S. military history. The M14 may not turn out to be a disaster, but considering the time and money spent on it the results are certainly disappointing. At least this is the opinion of retired four-star Marine Gen. Vernon E. Megee, former Commander Fleet Marine Force, Pacific, and a rifleman’s rifleman from Haiti and Nicaragua to Iwo Jima. General Megee’s capsule description of the M14: ‘They labored mightily and brought forth a mouse.’

    But the punch line of the M14 story is even more fantastic than the blunders in the rifle’s development. Now that the M14 is in production and is being issued to troops, it turns out that the rifle is not being put to the use that the Army claimed required its development in the first place. A fully automatic rifle, the M14 was developed to replace the semiautomatic M1 rifle. But 90 percent of the M14s currently being issued are set for semi-automatic fire only.

    The M14 rifle is a case of too little and too late. The rifle represents too little improvement on what we’ve already got – the M1 Garand. The new design has come along so late that the rifle is probably already obsolete.

    The situation is bad enough. Far more disturbing is the mounting evidence that the M14’s design contains some potentially dangerous flaws.

    The main weakness lies in the gas cylinder and piston that operate the M14. The system is complicated and finicky beast built to such tight tolerances that it almost invites jamming in combat conditions. But rather than openly redesign the rifle the Army had chosen to quietly do a series of ‘modifications’ on it that bear all the earmarks of a doctoring job to save the M14 from public exposure as a failure. This sort of attempt to make a bad bet come out all right is a hallmark tradition at the Pentagon.

Fortunately, Armalite and its chief engineer, Eugene Stoner, already had an alternative in the wings. 

    The AR Alternative:

    In the 1950s, the Fairchild Engine and Airplane Corporation decided to branch out into small arms and incorporated Armalite as a subsidiary for that purpose. Armalite hired Eugene Stoner as its chief engineer, and decided to enter the Army's trials for the replacement of the M1 Garand, with its chief competition being the Army's in-house T44 which would go on to be the M14. 

Different iterations of the AR10 (Source: "A (Not So Brief) History of the M16"--Pew Pew Tactical)

    Armalite's entry into the Army trials was the AR10 shooting the newly adopted 7.62 NATO cartridge. Because of Armalite's background in aeronautics, the rifle made use of advanced aluminum alloys and plastic composites to reduce its weight. This was further assisted by the elimination of a gas piston and operating rod by instead using an innovative direct impingement system where the gas was ported directly into the bolt carrier, effectively turning the bolt and bolt carrier into the rifle's gas piston. This system necessitated the use of a spring and buffer in a straight line behind the bolt carrier and, therefore, a stock that was in line with the bolt and barrel. This had the benefit of reducing muzzle climb. And by using a separate pistol grip from the stock, the weapon promised better ergonomics. Without going into detail, between some genuine problems that cropped up and the Ordinance Department doing everything it could to tip the scales in favor of the T44, the AR10 did not win the competition.

    While that normally would have been the end of the story for Stoner's design, General Willard Wyman, Commanding General of Continental Army Command (CONARC), had been impressed with Armalite’s AR-10. He personally asked Stoner to develop a smaller version of the AR-10 as part of evaluations of what were then referred to as Small Caliber High Velocity (SCHV) rifles. The testing took place in 1958 and pitted the M-14 against light weight SCHV rifles submitted by Winchester (using a .224 round) and Armalite's AR-15 (using a .222 round developed in conjunction with Sierra Bullets and Remington). Despite outright sabotage by Army Ordinance, the Armalite rifle performed admirably in the tests. A 1959 report, "Rifle Squad Armed With A Lightweight High-Velocity Rifle", found that a squad of 5 to 7 men armed with LWHV rifles would have better hit distribution and greater hit capability than an 11-man squad outfitted with M-14 rifles. Moreover, "[b]y opinion poll, the experimentation troops favor the LWHVR system, as represented by Armalite, because of its demonstrated characteristics of lightness in weight, reliability, balance and grip, and freedom from recoil and climb on full automatic (ease of firing)." The primary recommendation for the Armalite was a redesign of the sights to bring its accuracy up to that of the M-14. The report recommended that the Army develop a LWHV rifle "with a view toward early replacement of current rifles."

    Army Ordinance dug in its heels at this, with the result that the Army rejected any further efforts to develop or adopt the AR-15. By this time, Armalite had sold the rights to the AR-15 to Colt in order to regain some of its investment, and Colt continued the push for acceptance of the AR-15. As part of its push, Colt hosted a July 4, 1960, shoot with Air Force Vice Chief of Staff General Curtis LeMay. LeMay was very impressed with the weapon. He also realized and understood that his airmen guarding airbases did not need a heavy infantry weapon like the M-14. When he became Air Force Chief of Staff in the summer of 1961, he declared the AR-15 to be the official rifle of the Air Force and placed an order for 80,000 AR-15 rifles to be procured over the next five years, with an initial delivery of 8,000. The Pentagon fought back, but on May 15, 1962, Congress finally granted the Air Force’s request, and the Air Force had its first AR-15s within 72 hours.

    Unbeknownst to Army Ordinance, other events were in the work that would ultimately doom the M-14 and lead to adoption of the M-16 as the standard infantry rifle. In 1961, the Advanced Research Projects Agency (ARPA) sent several AR-15s to Vietnam for testing by Special Force as part of project AGILE. The results were positive, and so this was followed up with another 1,000 weapons being sent to Vietnam for evaluation. Field test results from military advisers and a Ranger battalion praised the AR-15’s reliability.

The reports were glowing, especially about the phenomenal reliability of the weapon. There were no broken parts reported in the firing of 80,000 rounds during one stage of the tests. In the whole period, only two replacement parts were issued for all 1,000 rifles. The report recommended that the AR-15 be shipped in bulk to South Vietnam as standard equipment for the ARVN soldier. 

The testing was also notable for the AR-15's stopping power and devastating effectiveness, and the troops involved cited it as “the best ‘all around’ firearm in existence.” The results were spectacular, with gaping wounds and the heads or appendages blown off of some victims. In fact, the wounds were so gory that they were classified for decades.

    This comparison between a heavier .30 caliber bullet and the lightweight .223 round has been confirmed by subsequent experience. From a Global Security article:

Two US Army doctors who evaluated AR-15 wounds at an Army hospital in South Vietnam in 1966 reported that while wounds inflicted at close range had small entrance and exit holes, those at larger ranges exhibited small entrance holes, but gaping exit wounds, devastated area of soft tissue and even bone, often with loss of large amounts of tissue, with disintegration of the bullet, and minute splattering of lead.

Alexander Rose related in his book,  American Rifle, about its performance in Iraq:

    The AK-47 gets grisly PR about having killed more people than any other gun—mostly a result of its widespread use by psychopathic regimes. But interestingly, in terms of deadliness the AK-47 suffers by way of comparison with the M4. Testing and unfortunate experience show that the AK's bullet, after entering human tissue, tends to take a straight path. It pushes in headfirst to a depth as great as ten inches, and for that reason many pass through the body in one piece, leaving behind less severe wounds. When hitting, say, the abdomen, an AK-47 projectile will cause the same “minimal” degree of disruption as a handgun bullet.

    By way of contrast, an M4/M16 bullet, shot into the abdomen at less than two hundred yards, will penetrate headfirst for about 4.7 inches, then yaw to 90 degrees before breaking in half. The pointed half remains in one piece, but the base is torn into shards that perforate tissue in many places. This fragmentation and the yawing enhance lethality by creating more traumatic internal wounding. [ pp. 403-404]

    But back to our story, the ARPA research resulted in the Army being forced to reevaluate the AR-15. The Army's testing still favored the M-14. Intrigued as to the disparity between the Army's testing and reports from Vietnam, "Secretary of Defense Robert S. McNamara ordered Cyrus Vance – then-Secretary of the Army – to look into why that was happening, and he discovered that the Army was (purposefully) testing match-grade M14s against off-the-rack M16 rifles," as well as cherry picking shooting conditions for the tests of the M-14.

    The discovery of the Army's cheating was the last straw. In January 1963, McNamara ordered the adoption of the AR-15, and production of the M-14 was terminated. Initially, the M-16 was issued to airborne and special operations troops, but as U.S. involvement in the Vietnam War escalated and increasing numbers of troops were deployed, regular troops also clamored to use the AR-15, and so it became the standard infantry rifle. Interestingly, we would see a repeat of this after adoption of the M-4 by special operation troops, when regular troops would again demand to use the M-4 over the longer and heavier M-16, leading to the M-4 to become the standard issue infantry weapon.

    Robert Conquest’s Third Law of Politics Strikes Again:

    The story of the AR-15's adoption as a military weapon was still not complete. After the Army was essentially forced to adopt the M-16, there were a series of actions taken by the Army that could be viewed as either extreme incompetence on the part of Ordinance officials or their last gasp attempt to sabotage the M-16 even if it resulted in the deaths of American troops. All of these changes resulted from the Army varying from Stoner's design; it is notable that the Air Force, which purchased M-16s manufactured per Stoner's original specifications, used those rifles without issues up through the 1990s when they began replacing the M-16 with the M-4 carbine. The changes adopted by the military and the problems that ensued included:

• The 7075 T6 aluminum specified by Stoner was replaced by cheaper 6061 T6 aluminum that corroded over time.
• The 1:14 twist of the rifling was sped up to 1:12 in order to better stabilize the bullet in cold arctic air, but also reduced the lethality of the weapon. 
• A manual bolt closing device, called the forward assist, was added. While it is not clear that it did any harm, Stoner believed it was unnecessary and it may have encouraged soldiers to push the bolt closed on defective ammunition and/or when the bore was too dirty to operate reliably.
• The chrome lining of the bolt, chamber and bore called for in Stoner's design was done away with. This resulted in corrosion and build up of fouling that impacted the reliably function of the rifle, including causing cases to become stuck in chambers. It also made it more difficult to clean the weapon in the field. 
• Instead of using the IMR 4475 powder around which Stoner had designed his weapon, the Army decided to use older ball powder produced by a different company. This powder was dirtier--it produced more carbon fouling and buildup than the IMR 4475 powder requiring more frequent cleaning to avoid problems with loading or extracting casings. It also burned at different pressure peaks, considerably speeding up the firing rate at full auto which not only threw off the timing of the weapon, but also caused excessive wear and tear.

At the same time the Army was ensuring the rifle was going to run dirtier and more easily suffer from corrosion problems, the Army also failed to issue cleaning kits to soldiers who were left with the belief that the weapon didn't need cleaning.

    The combination of all the foregoing turned the M-16 from a weapon praised for its reliability and effectiveness in the early trials in Vietnam to one that was cursed by its users for frequent jamming, stuck and broken cases, and overall poor performance resulting in countless deaths just as U.S. troop involvement in Vietnam were being ramped up. 

    An Improved Rifle:

    Ultimately, Congress investigated, and recommendations were made which resulted in the changes that led to the M16A1 rifle. As this National Interest article relates:

By 1967 Colt and the Army agreed to implement a number of modifications to the rifle to increase reliability. A heavier buffer would slow down the M16’s rate of fire, the plastic stock would be made more rugged by using thicker plastic, and the chamber and barrel would be chrome-plated to resist corrosion. Colt would treat steel parts with a phosphate coating to resist rust and improve aluminum anodization. The first rifles with these changes were in the field by late 1967, with the rest deployed by late 1968.

Those changes eliminated most of the complaints regarding the platform. 

    Despite the foregoing, the M16 design was a superior weapon to those fielded by Soviet backed forces. James O'Connell's paper, "The M16 in Vietnam: A History of the Weapon’s Effectiveness in the Vietnam War and the Necessity of its Creation" describes and explains the impact on the fighting man armed with an M-16 (footnotes omitted):

    ... The M16 was ergonomically a superior weapon to the AK-47 in almost every way. Reloads on the M16 were faster, getting empty weapons and vulnerable soldiers back into the fight much quicker. This was mostly due to the general design of the weapon, since the M16 had a magazine well that guided the user’s hand. It was also due to the fact that when the rifle ran out of ammunition, the bolt locked to the rear, indicating the need to reload. The AK-47 lacked such a feature, making it difficult to quickly tell when you needed to reload. The selector switch, which the user could manipulate to set the weapon to safe, semi-automatic, or full auto, was much easier to access on the M16 as well. The selector lever on the AK-47 was on the right side, and was designed to be very large, requiring the user’s full right hand to manipulate. As opposed to the M16, which had just a small switch on the left side, accessible by the user’s thumb while holding the pistol grip.

    These features were minor when compared to actual use of the weapon in combat, specifically the ability to hit a target. A study was conducted on the performance of the M16 and AK-47 by the United States Army in May of 1990, overseen by Lieutenant Colonel J. M. Weaver Jr. The study concluded that an M16A1’s probability to hit a target without any aiming errors was 100% up to 300 meters, 73% at 600 meters, and 39% at 800. Rates for the AK-47 were 94% at 300 meters, 54% at 600 meters, and 31% at 800 meters. This is due to the heavier cartridge that the AK-47 sports, combined with its inferior and unreliable iron sights. However, a comparison of accuracy is not all that can be done to test the effectiveness of the M16.

    Penetrative ability also mattered, and the AK-47 did seem to outshine the M16 by blasting through almost anything in front of it. That might sound like an advantage to the credit of the AK-47, but that is not necessarily true in the context of war. Research suggested that a smaller, faster moving round, would do more damage than a heavier round. The creator of the original M16, Eugene Stoner, explained that while smaller bullets are more stable while flying through the air, they become unpredictable after making contact with a target. This can cause more internal damage, which is more likely to result in a fatality. This means that even a poorly aimed shot, as long as it makes contact with an enemy, can still potentially do more damage than a bigger bullet.

    Dr. Martin L. Fackler conducted tests at the Wound Ballistics Laboratory in San Francisco, California in 1990, and determined that while the AK-47’s penetrative power was superior, it actually caused less damage to the human body. His studies confirmed what Eugene Stoner had envisioned with his weapon design. The large mass of 7.62 rounds propelled it clean through flesh, creating a clear path that could be easily patched up. A shot from the M16, however, with its lighter round, would create more internal bleeding. Once the lighter round hit a solid target, it tumbled, which created massive internal bleeding. This could not be fixed during a firefight and required surgery to repair. Even if the shooter missed a vital organ, there was still a chance that the round would bounce around inside the victim’s body and cause enough damage to kill him later.

The effectiveness of the .223 was so apparent in Vietnam, that the Soviets immediately set about developing their own small-caliber, high velocity round: the 5.45 x 39 mm which would be introduced in the 1970's in a updated version of the AK-47 and AKM called the AK-74. Russia, today, still uses the 5.45 round as its primary infantry round.

    Placing an automatic rifle into the hands of the common trooper or marine also had an impact on moral and effectiveness. O'Connell continues (footnotes omitted):

    ... The M16 boosted the confidence of soldiers. The ability to lay down effective fire compared to the automatic riflemen beside them made them more self-assured that their role in their squads was as valuable as others, which is incredibly important on the battlefield. Samuel L. A. Marshall, a combat historian during the 1940s and 1950s, conducted a study that concluded that nearly four fifths of combat soldiers in the European theater of World War II never fired their weapons during battle. The BAR, a squad-level, shoulder-fired machine gun used in the Second World War, was a weapon of incredible stopping power. There would typically be one or two per squad of twelve men, and engagements would often begin by the BAR man opening fire first to produce the most casualties as early as possible. Firing would begin with him, and spread out from there, which meant that the nearer a man was to the BAR, the more likely he was to fire. Many believed that using the semi-automatic M1 was futile because of the raw power behind the BAR. John Keegan, a prominent military historian, writes in his book, The Face of Battle, “Infantrymen, however well-trained and well-armed, however resolute, however ready to kill, remain erratic agents of death. Unless centrally directed, they will choose, perhaps badly, their own targets, will open and cease fire individually, will be put off their aim by the enemy’s return of fire, will be distracted by the wounding of those near them, will yield to fear or excitement, will fire high, low, or wide.”

    Most infantrymen could not see their targets but knew generally where they were and would often either fire blindly or hold fire entirely. The BAR man, in contrast, could suppress an area with relative ease, which discouraged anyone else from even trying. Because of how powerful the BAR was, many ambushes would be over as soon as they started; there was often no need for anybody else to participate in the action. This was a problem that needed remedy, and the M16 offered a solution. With all the advantages of automatic fire, recoil control, and ballistic reliability, soldiers felt that their efforts were contributing more to the fight than just shooting leaves and grass.

In short,  O'Connell concuded:

    The M16 proved to be a superior weapon to that of the enemy’s AK-47. The M16 excelled in crucial comparisons between the two rifles — namely in accuracy at long range, accuracy in fully automatic fire, quick reload capabilities, its lighter weight (both for the rifle itself and for its ammunition), and the damage possible against an enemy force. Having the M16 also gave American soldiers an edge over the Viet Minh because it served to boost soldiers’ confidence during a firefight, which helped eliminate complete reliance on the squad’s machine guns. ...

And:

The M16’s lighter caliber made whatever wound it created much deadlier than the heavier counterpart of the M14, because of the ballistic behaviors the M16 displays when hitting a hard target. Even the best combat medics cannot treat internal bleeding.

    Other Notable Events:

    Because we are ultimately interested in the AR-15 as a civilian weapon, I'm not going to delve into detail of subsequent military developments save to note that the military, led by the Marines and their desire for a more accurate rifle effective at longer ranges, eventually adopted a heavier barrel and more refined rear sights; and, starting in 1990s and accelerating after the invasion of Iraq in 2003, adopted the shorter barreled M-4 Carbine; and with the development of the Picatinny accessory and optics rails (itself derived from the civilian Weaver rail system), increasingly began using optics, lights, and lasers on the weapon system.

    On the civilian side, Colt had offered a semi-auto civilian version of the AR-15 since even before its large military contracts in the 1960s. But after the expiration of its patents, Jim Glazier and Karl Lewis started manufacturing the first civilian versions of the AR-15 in 1989 under the name of Eagle Arms. Nevertheless, the rifle probably would have remained a niche item but for four events.

    First was the passage of the 1994 Assault Weapons Ban (AWB) which prohibited semi-auto firearms deemed to have too many arbitrary and mostly cosmetic features also found on modern military weapons. This directed a great deal of public attention on these firearms which sparked increase interest in owning such weapons. Because the AWB had little impact on the availability of "neutered" weapons and expired in 2004, the AR and other modern semi-auto rifles gained in popularity.

    Second was 9/11 and the Global War on Terror (GWOT). Military personnel returning from active duty naturally wanted rifles for target shooting, hunting or self-defense that were similar to those on which they had trained and used in the military.

    Third was the popularity of first person shooter video games which, just as with soldiers and marines involved in the GWOT, resulted in players interested in obtaining civilian copies of weapons used in the video games.

    Fourth, due to it growing popularity and reduced cost of manufacturing, more and more companies entered the AR market producing the rifles and/or accessories. This meant that not only were costs driven down as compared to other weapons, but that weapons were available in endless variations and in prices from that affordable to the common working man to high-end weapons appealing to the die-hard shooter or collector. 

(Source)

Basic Features and Operation:

   The basic parts of the AR are (from back to front), the rear stock (if it is a rifle), buffer tube (which may or may not be completely enclosed in the rear stock) containing a weighted buffer and recoil spring, an upper receiver containing the bolt carrier, bolt, and charging handle, and into which is screwed the barrel and barrel extension. Below the upper receiver is the lower receiver--the serialized part considered to be the weapon under federal law--which contains the fire control group (trigger, sear, and hammer), safety selector to engage or disengage the safety, the magazine well and mechanism to lock in the magazine, and the bolt hold open and bolt release lever. The upper receiver is connected to the lower receiver by two push pins--one on the front and one on the rear--allowing easily disassembly and cleaning of the weapon. Both pins have retention detents that prevent the pins from being fully removed and lost. 

    Ahead of the upper receiver is the barrel and barrel extension. The extension is simply a part that attaches to the rear of the barrel and is machined to accept the barrel lugs and lock the barrel and bolt together at the moment a round is fired. To the barrel is attached the gas block and gas tube, which is where the gas is diverted from the barrel (though the gas port) and redirected down the gas tube. The barrel and gas tube are surrounded by a hand guard that both protects the gas tube and keeps the shooter from burning his or her support hand. Depending on the model of weapon or selection of the user, the gas block may incorporate a fixed front sight, and the muzzle of the barrel may be threaded to accept a muzzle device such as a flash hider, muzzle break, or sound suppressor. 

    The AR-15 is a semi-automatic weapon that fires one round per pull of the trigger. It uses a gas operated system commonly termed a direct impingement system to unlock the bolt and drive the bolt and bolt-carrier backward, ejecting the spent cartridge and stripping a new round off the top of a detachable box magazine that inserts ahead of the trigger guard. Most semi-auto rifles that employ a gas system use a piston system where the gas is bled off from the barrel and immediately impacts the piston and drives the piston backward. Depending on the system, the piston may strike a rod which in turn pushes against the bolt carrier, or the piston may be connected via an operating rod to the bolt carrier. In the case of the AR, however, the gas travels down a long gas tube through a "gas key" on the top of the bolt carrier, and down into the bolt carrier behind the bolt and exerts force directly backward against the bolt carrier. Much like the piston rings on the pistons of a car, the bolt has three gas rings that fit on it to prevent the gas from blowing forward around the bolt instead of backward against the bolt carrier.

    As the bolt carrier is driven backward, it causes the bolt to rotate and unlock from the what is called the barrel extension. As the bolt carrier is driven backward, the spent cartridge is ejected to the right through an extension port on the upper receiver. 

Left Side of AR

Right side of AR

    Basic operation is as follow. 

    Loading: A loaded magazine is inserted into the magazine well (preferably using the left hand if you are a right handed person) and pressed into place. Most people will slap the bottom of the magazine to ensure it is fully seated and locked into place. 

    If the bolt is locked back, then using the left thumb, press on the top of the bolt catch to release the bolt. Some people will alternatively lightly slap the bolt release with the pad of their left hands to make sure it releases. The bolt release will then be pushed forward by the buffer spring stripping a cartridge off the magazine and into the chamber.

    If the bolt was not locked back, then the user will need to pull the T-shaped charging handle backwards as far as possible and then let go so that the buffer spring can then push the bolt home, stripping a cartridge off the top of the magazine and chambering it. If you look at a standard charging handle for the AR, you will see that it has a latch on the left side that releases the handle from a catch so it can be pulled back. The arms of the handle forming the T are pretty short on the standard weapon, but you can purchase after market handles with longer arms as well as ambidextrous handles that can be released from either side. I would recommend at least getting a handle with larger arms to make it easier to grasp the handle. 

    The Safety: The safety lever is also on the left side of the firearm so that it can be operated by the thumb of the right hand grasping the pistol grip. Ambidextrous safeties are also available, and definitely recommended if you are left handed. As for the safety lever, if it is pushed so the lever and arrow is pointed straight up and down, the weapon is ready to fire. Pulling the lever backward with the thumb 90 degrees so that the lever is to the rear and the arrow is pointing forward puts the weapon on safe. This serves the purpose that if the weapon is dragged on the ground, it will naturally tend to pull on the selector lever in such a way as to put the weapon on safe. Note that the safety cannot be engaged unless the weapon is cocked and ready to fire. 

    Firing: The weapon is discharged by pulling the trigger which releases the hammer, striking the firing pin, which in turn strikes the primer and ignites the powder in the cartridge. Because the civilian AR-15 is a semi-automatic weapon, it will only fire one round per pull of the trigger. 

    The Dust Cover and Ejection Port: One of the things that makes the AR-15 so reliable is that it has a dust cover that completely covers the ejection port and locks into place to prevent debris from getting into the action. The dust cover has a latch at the top that locks it into place. To close the dust cover, push it until if fully closes and the latch clicks. Operation of the bolt, whether by firing the weapon or pulling back the bolt carrier with the charging handle, will pop the cover open. This means that the cover does not need to be opened prior to firing the first round--it will open as the bolt carrier recoils. Pretty nifty!

    Take Down Pin: As noted above, the upper and lower receivers are held together with two pins. The front pin is called the pivot pin, while the rear pin is called the take down pin. That is because to clean the weapon, all you need to do is push the take down pin out (pushing from the left) with a cartridge or pen until it locks into its detent, and then the upper receiver will hinge or pivot on the front pin, allowing you to remove the bolt carrier group and provide access to the fire control group and the breach end of the barrel for cleaning.

    Winter Trigger Guard: You will notice in the photographs of the military weapons, the bottom of the trigger guard is straight, while the civilian weapons have a rounded bottom. The straight trigger guard is a winter trigger guard. By pushing in a detent on the rear of the trigger guard with the tip of bullet, it will release the trigger guard to pivot downward to allow the use of a gloved finger or mittened hand to operate the trigger. The curved trigger guards do not do this--they are oversized for the express purpose of allowing a gloved finger to fit. 

    Militaries around the world vary on how they handle trigger guard designs. The U.S. Army has traditionally favored a smaller trigger guard that was less likely to get a branch or stick caught in it and accidentally discharge the weapon. Unfortunately, these trigger guards are too small for serious cold weather clothing, requiring a special winter trigger device allowing someone with thick gloves or mittens to actuate the trigger. Alternatively, most other militaries (including the Soviets) used an oversized trigger guard to allow a gloved finger to be used. The AR-15 takes the best of both worlds, allowing a small trigger guard in most cases, but capable of being opened up for use by soldiers in cold weather gear.

Why The AR-15 Makes A Great Rifle For Preppers And Survivalists:

     There are no do-it-all rifles. As Ron Spomer writes in his article, "How to Pick One Rifle to Hunt Everything":

If you want one gun to rule them all, you have to make it a 12-gauge shotgun. Why? Because it can shoot pellets for upland birds, waterfowl, small game, and even—with buckshot—predators and deer. Load that 12-gauge with slugs and you’re ready to tackle any big game short of an elephant. And I wouldn’t bet against the 12-gauge on that, either.

But even selecting the shotgun is a compromise because you have a weapon of limited range which, in standard configurations, is large and slow to reload, and which ammunition is expensive and bulky. My point in this is that it is unrealistic to expect a rifle to be able to do everything well, and instead focus on something that fulfills most of the important functions you will need in a weapon after a SHTF or WROL event.

    So the question to ask yourself: what will it be like post-SHTF? 

    Back in 2014, I posted an article with the title "The Top 5 Firearm Myths Among Preppers."  Although chastened by my betters, I still stand by what I stated there, including that up to and until SHTF, your primary weapon will be your handgun. The main reason for this is because there are very few instances where you could legally justify shooting someone in self-defense at distances beyond the effective range of a handgun. Also, in my opinion, the benefits to picking a handgun for defense inside your home outweigh the advantages offered by the rifle. Finally, there is a benefit to being able to carry a handgun concealed all day long. There are some exceptions to general rule, such as when you need the firepower offered by a rifle or protecting livestock. Grant Cunningham covers this in his book Protecting Your Homestead: Using A Rifle To Defend Property On Your Property. (The Amazon link is for your convenience--I don't make any money off it). But these are the exceptions. 

    During and after SHTF may present completely different circumstances. FerFal has written extensively about the economic collapse in Argentina. In that situation, there wasn't a societal collapse, but crime became more prevalent; your primary self-defense weapon in that case was still the handgun, however. Contra to most prepper visions of SHTF, food and employment was most plentiful in the cities because production and distribution chains still functioned.

    Selco has written extensively about the collapse of Yugoslavia and the siege of Sarajevo. In that case, we saw a governmental collapse followed by an almost spontaneous ethnic and religious segregation described as a civil war. Because this was a war that was fought in the shadow of NATO, however, it was still somewhat constrained. There the choice of weapon was a mixed bag: a military rifle seems as though it would have been a plus in dealing with violent gangs and enemy soldiers, but a handgun may still have been the better option for many of the people holed up in Sarajevo where crime was still the primary threat and discretion the better part of valor. 

    Most widely read survivalist and prepper writers in the United States, no matter the triggering event,  foresee a sudden break down of the food distribution networks and/or economic system followed by massive civil unrest following a SHTF event: rioters and looters in the cities, hordes of the unprepared (sometimes referred to as the Golden Horde) spreading out from the cities to find food, shelter, and safety, and roving gangs of outlaws even reaching out into the countryside and menacing small towns and individual homesteads. A nuclear war might reduce the number of the Golden Horde at the outset, but it is believed that it will still produce an outflow of people into rural areas. According to this view, cities are death traps to be avoided or from which the prepper will have to escape (thus the focus on bug-out-bags (BOBs) and bug-out-vehicles (BOVs)). Conversely, rural areas are considered places of refuge if you have a homestead of your own or some other valuable skill to trade for food and shelter. The luxuries that come with civilization and cities will be gone as we plunge into a new dark age. "Think of life on the frontier in the 16th century," wrote one author. Although I think he meant the 17th or 18th centuries, the point is well taken: under this model you will likely be engaged in subsistence farming augmented by hunting/trapping or fishing, in a hostile wilderness, with spare parts for firearms (or anything else for that matter) largely unobtainable.

    I have my doubts about the standard survivalist/prepper vision of post-SHTF. For one thing, the standard prepper theory tends to ignore just how large is the population of the United States. Although official census figures have yet to be released as of this writing, the population is approximately 330,000,000 people--or 1/3 of billion people. Unlike in most prepper fiction, these people are not going to magically disappear or quietly sit in their apartments or McMansions to starve. Especially when "[a]bout 40% of Americans say they or someone in their household owns a gun, and 22% of individuals (about 72 million people) report owning a gun, according to surveys from Pew and Harvard and Northeastern." We know that these polls probably understate the true number of gun owners because the poll numbers are all over the place, and other polls have shown a significant number of people agree that it is not any business of a pollster as to whether a person has a firearm or how many. I would note that in 1978, 51% of households reported owning firearms. I'm sure that the numbers have only increased since 1978, not fallen. 

    Second, those living in America increasingly hate one another. According to polling from this past October, "[s]ixty-one percent of Americans are worried that the U.S. could be on the verge of another Civil War, while 52% say they’ve already started stockpiling food and other essential in anticipation of social unrest." Another October 2020 "poll showed that when voters were asked to rate divisions in America on a scale of 0-100, with 100 being the 'edge of a civil war,' the mean response was 67.23." 

     In other words, no matter the trigger--be it social or political upheaval, an economic crises, loss of a war, or some other largely national disaster--post-SHFT will be a period of civil war. Because we are so thoroughly intermixed, this war will begin at the neighborhood level. Victories and losses will act to further segregate the factions which will inevitably coalesce into opposing camps. Those living in rural communities will likely see their resources cut which will cause their own crises; and when the "Golden Hordes" arrive, they will not be rowdy criminal gangs popular in prepping fiction, but will live up to their namesake by destroying or driving all before them. Your choice will be to stay and fight or flee to an area of refuge. Consequently, the best survival weapon will be one that allows one to function as part of a "well regulated militia". And what better than a weapon that is largely compatible with what is already being used by the military.

    But even ignoring all that and going with the standard prepper scenario, the AR-15 is still a great weapon for the prepper.

    Earlier, I referenced an article at the Readyman blog with the title, "A Combat Rifle and a Prepper Rifle are NOT the Same Gun." The author compiled a list of five traits desirable in a pepper rifle that is useful and that I will use to show why an AR-15 is probably an ideal prepper rifle. For you that slogged through the long background and history of the AR-15, your efforts will be rewarded here because many of the same considerations that made the AR-15 the ideal weapon for soldiers in the 1950s and 1960s also make it a great prepper rifle.

    The first point that the Readyman article raises is that "a prepper will probably need to have their gun on them while living everyday life" as he or she goes about "gardening, building, cooking and playing with his kids, hopefully with his rifle within arms reach every minute of every day and night." The author goes on to comment that "[a] prepper rifle must be compact and light and fill multiple rolls," and that "[t]he difference between an eight-pound rifle and a six-pound rifle would likely be the difference between having a gun and not having a gun on-hand when trouble showed up" or taking some game. 

    This is reminiscent of the military criteria for the original M-1 carbine, and was one of the roles envisioned for the original M-16: to be a lightweight rifle of less bulk and size than the M-1 Garand (or M-14) that could be used by support troops as well as front-line troops. In fact, the primary reason that the M-16 initially proved so popular with troops was because of its light weight and maneuverability. And when the M-16 started putting on the pounds, we saw troops clamoring for the lighter and handier M-4 carbine. The M-16A1, M-4, and Ruger 5.56 come in at about 6.5 lbs each. The Saint Pistol listed earlier had a base weight of 5 lbs 6 oz. Thus the AR, depending on the exact configuration, can be a lightweight and compact weapon for everyday carry after the SHTF.

    The second point raised in the Readyman article is that "[a] prepper rifle should be simple, and a prepper should settle into two or three weapon systems, probably for life." The AR-15 is both mechanically simple and simple to operate. It had to be since it was intended to be easily learned and used by conscripts that may have never handled a weapon before and had no interest in being in the military anyway. Firing the weapon is straight-forward: pull the trigger and the weapon automatically feeds the next round into the chamber. There is no need to learn how to quickly and efficiently manipulate a bolt and bolt handle between each shot, or the lever of a lever action. Reloads are also easy and efficient because you simply insert a new magazine.

    Field stripping is probably the easiest of most any semi-auto rifle devised. Simply push out the rear take down pin until it clears the upper receiver, tilt the receiver up, remove the cocking handle and bolt carrier group (BCG) and that's it: you are now ready to clean the rifle. It is also one of the simplest rifles to break down further for detailed cleaning or repair--far simpler than a lever action if you need to remove the bolt or work on the action, and simpler than bolt-action rifles if you need to get into the fire control group. And, due to its popularity, it is easy to find other classes of weapons using the same manual of arms as the AR-15.

    The third point raised in the Readyman article is that "[a] prepper rifle should provide the greatest chance of hitting a target day or night.  That may require an electronic sight or, at best, a laser or IR laser (with NVGs.)" The AR-15 is an inherently accurate platform. Most every AR-15 sold today comes with attachment points for telescopic sights or other optics, and for attachment of a weapon light. 

    The fourth point raised in the Readyman article is that preppers will not be fighting and winning engagements, but, if attacked, working to break contact. Also, the author notes, the rifle will be used for other purposes, including hunting game. Thus, he advises that you "[t]ake into consideration distance, available game animals, options of resupply, reload-ability, and probable self-defense scenarios." If you are trying to break contact, one of the most important considerations is to be able to lay down suppressive fire while moving away. Although the civilian AR-15 lacks the full automatic fire of a military weapon, impairing its ability to produce effective suppressive fire, it can still be fired fast enough and can make use of a large enough magazine to be somewhat effective in this role. Certainly better than a bolt-action or lever action rifle or a larger caliber semi-automatic.

    As for distances, the studies following WWII and the Korean War showed that almost all combat was at 300 yards or less, with a majority at less then 160 yards. If you study up on distances for hunting and taking game, you will see similar numbers. 

    Although the 5.56 is not generally considered adequate for large game, it can be very effective on small and medium sized game including deer even when using full metal jacketed ammunition, as discussed below in more detail when I compare it to the .308 and 7.62x39mm. And, as also discussed below, if you believe the .223/5.56 is deficient for hunting, the AR-15 and its larger version, the AR-10, can be had in larger, more powerful calibers.

    The 5.56/.223 cartridge does not in my experience offer any additional difficulties when it comes to reloading compared with other cartridges other than having to trim the primer pockets on military brass. It does seem more prone to stretching of the case neck, but you should be checking case length anyway and trimming as necessary. Typical powder charges range between 24 and 28 grains, which is nearly half of the 45 or so grains typical of the .308 or .30-06, so you will get more loads from a given pound of powder. Because it is one of the most popular cartridges in America, it will be easier to find or be resupplied with this ammo than most any other rifle cartridges.

    The fifth point in the Readyman article is that "[t]here will probably be limited ammunition and almost no ammunition for training others," and you should "[c]ount on fighting like an Old West settler, with limited ammunition for homestead defense." This is a good point. The AR-15 has such minimal recoil that it makes a good rifle for training even women and children with limited ammunition. Also, outside of the severe ammo buying panics, the 5.56 is one of the least expensive rifle calibers available on a per round basis and, for that reason, you can stock up on more for any given sum of money than practically any other caliber.

    And, picking up where the Readyman article left off, here are some additional reasons the AR-15 makes a great prepper rifle:

Miss America 1962 with the original M-16
(Source).

    The sixth point in favor of the AR-15 is that, even with a fixed length stock, it can easily be managed by people of slight stature including women and children. Throw on an adjustable length stock, which is the default anyway on most rifles and carbines, and it is even easier for a person of a smaller stature to use. Thus, it makes a great rifle for your family to standardize around.

    And speaking of adjustable stocks, the seventh point in favor of the AR-15 is that its modularity makes it a great platform for configuring to the specific shooters needs and desires. The following is not a complete list of ways to configure or accessorize the weapon, but it covers the major points.

    Accessory/Scope Rail: It is rare anymore to find an upper receiver that is not a "flat-top": having no carry handle or rear site, but instead having a section of Picatinny rail along the top of the upper receiver. This makes it easy to mount a telescopic sight or red-dot sight, together with back-up iron sights (BIUS).

    Handguards: The typical military handguard for the AR for most of its service life was a round, two-piece guard that fitted into the rear receiver at the back, and the gas block/front sight assembly on the front. Later, the military switched to a "quad-rail" system where the handguard also sported Picatinny rails at the 12, 3, 6, and 9 o'clock positions. While very tough, these handguards are also heavy--one of the reasons that military ARs have crept up in weight. Civilian handguards have moved past this to systems that not only allow you to "free-float" the barrel to minimize outside forces impacting the barrel and, thereby, accuracy. Also, rather than having a weighty quad-rail system, these handguards offer slots at various positions to allow the addition of an accessory rail or, increasingly, allowing devices to be attached directly via the slots. The two most popular systems are Key-mod and MLOK. The MLOK system is the most popular and would be my recommendation simply because of the wide availability of accessories designed to be used with the MLOK system. Nevertheless, in order to keep the weight down, I would keep attachments to the handguard to a minimum: a weapon light and, perhaps, a hand-stop or vertical foregrip. 

    Triggers: The quality of triggers varies considerably depending on the manufacturer. However, there are many aftermarket triggers available, including better quality triggers that simply replace the parts used in the weapon, to drop in units that combine the trigger, sear and hammer into a single cartridge. If you decide to go with a drop in unit, I would recommend that you keep a standard trigger set as a back up in case the drop in unit fails.

    Muzzle Device: The standard muzzle device sold with the majority of AR-15s is the A2 flash hider. It is cheap, short (doesn't add a lot of length to the barrel) and actually one of the best devices in the market to keep you from being blinded by the muzzle flash if shooting in dim light or in darkness. However, there are many other muzzle devices out there to reduce flash, reduce recoil (muzzle compensator), or combine features of both. And, if you want to go through the process demanded by the BATF (Bureau of Alcohol, Tobacco, and Firearms), you can register, pay a tax, and obtain a sound suppressor (aka "silencer") for your AR.

    Butt Stock: Most ARs sold today on the civilian market have some type of adjustable butt stock. These are designed to allow you to shorten or lengthen the length of pull (distance from the trigger to the rear of the stock) to fit different sized shooters or the same shooter, but wearing different thicknesses of clothing. There are many different options available from minimalist stocks without much of anything as to features (the main feature being light weight) to stocks that incorporate storage compartments or feature adjustable cheek risers, or are heavily built for the most trying of conditions.

    Barrel Length: The original AR sported a 20-inch barrel, and the effectiveness of the 5.56 cartridge is based around that length. That is, 20-inches is the optimal length for the gas system and muzzle velocity. However, other popular lengths are 18-inch, 16-inch (probably the most popular barrel length for the civilian weapon ), 14.5-inch in a short barrel rifle (SBR) or using a pinned and welded muzzle device to bring it up to 16 inches overall lengthy. For the pistol configurations (or an SBR) there are 10.5 inch and even shorter barrels available, although 10.5 inch is the shortest barrel recommended for the .223/5.56 cartridge. 

    The downside with the shorter barrel lengths is that you lose velocity and, therefore, terminal performance from the .223/5.56 round. My recommendation to a prepper would to go no shorter than 16 inches if you intend to use the .223/5.56. If you decide on a different caliber, the performance and necessary barrel length may vary. For instance, the .300 Blackout cartridge will achieve full powder burn after 9 inches or so, which makes it ideal for pistol length barrels, but reaches it full potential at 16 inches--anything longer is just adding addition weight without much if any increase in performance. On the other hand, some of the longer range cartridges need barrel lengths of 20-inches or more to reach their potential.

    Caliber: Even without stepping up to AR-10 sized receivers, the AR-15 design is offered in a multitude of calibers, including, but not limited to:

• .224 Valkyrie: this cartridge is based off the 6.8 Remington SPC case providing more room for a longer bullet and greater powder charge than the .223/5.56 round. This round is good for hunters and long range (1,000 yard) target shooting, but requires a longer barrel (20 inches or more) to realize its full potential.
• 6.5mm Grendel:  This cartridge was intended to provide a heavier bullet to be used at ranges out to 800 yards. It, therefore, makes a good hunting and target shooting alternative.
• 6.8mm Remington SPC: This is another cartridge intended to give the AR-15 more power at longer distances beyond 500 yards from the shorter M-4 configuration. It was hoped that it would be a replacement for the 5.56 for the military. While that didn't happen, it is notable that the lightweight cartridge intended for the new generation of military rifles uses a 6.8 mm diameter bullet. 
•  .300 Blackout: this is probably the most popular alternative to .223/5.56 in the AR-15. When firing lighter 110 or 125 grain bullets it is balletically very similar to the Russian 7.62x39mm, and in heavier bullets of around 200 grains or more is very easy to silence with a sound suppressor, without having to make any changes to the gas system. Other advantages to the .300 Blackout is that because it uses a pistol powder, it has full powder burn at about 9 inches, which makes it ideal for shooting out of a short (10 inches or less) barrel without excessive loss of energy or muzzle blast. Also, because it is based on the .223 case, it can use a standard AR-15 bolt and bolt carrier, and, at least when using lighter weight bullets, can use the standard AR-15 Stanag magazines.
• .350 Legend: The .350 Legend is a straight wall cartridge derived from the .223/5.56 case but using heavier .357 diameter bullets. There are states that have restricted deer hunting to straight wall cartridges and this cartridge was developed for hunting in those states. Based on the reviews that I've read and watched, this appears to be gaining popularity as a short range deer cartridge for the AR-15 platform.
• .450 Bushmaster: This is another straight wall cartridge for use as hunting cartridge with the AR-15 platform, but shoots .452 caliber bullets designed for the .45 ACP, .45 Colt, and/or .455 Casull. Thus, this is a cartridge capable of taking larger game at shorter ranges.
• .458 SOCOM: This is a cartridge based off the .50 AE pistol cartridge but with a reduced rim diameter to make it useable in an AR-15 platform. It fires bullets ranging from 250 grain up to 600 grain (although 250 to 350 seems typical), including bullets intended for the .45-70. Because it was originally designed as a military cartridge (for SOF), it was intended to use the standard AR-15 magazines and followers, albeit single stacked. This is another cartridge well adapted to taking larger game animals. 
• .50 Beowulf: Another straight wall cartridge intended to create the most powerful round that could be shot out of the AR-15 sized platform. It uses bullets in the 300 to 400 grain range.

Richard Mann has an excellent article at Shooting Illustrated providing an overview of the cartridges available for the AR-15 platform. 

    An eighth point in favor of the AR-15 is the ease of maintenance and repair. I've already mentioned how easy it is to break down the rifle for cleaning. But if you have to go beyond that to more serious repairs, the AR-15 is also more amenable to repair by the amateur than other rifles. For instance, other than an armorers wrench for the barrel nut or the buffer tube's castle nut, the AR-15 can be assembled (or disassembled) using simple, common and inexpensive hand tools and a bench vise (and even the vise is probably optional)--even going so far as to replace a barrel. The bolt is easily disassembled in order to replace a firing pin or broken extractor or extractor spring. Conversely, rifles such as the AK or G3 require a shop press and/or special dies to hold the pieces for the barrel pin or some of the other pins. 

    

    Finally, a ninth point in favor of the AR-15 is reliability. As related in the background, the troops that tested the original AR-15/M-16 raved about its reliability. Only when the Army deviated from Stoner's design did the M-16 become plagued with reliability problems. Once this were corrected, the AR-15 regained much of its reliability. 

    Today, you need only Google "AR mud tests" and you will find countless videos testing the AR-15 after being dragged through or covered with mud, and it operating flawlessly. The dust cover keeps most of the crud out of the mechanism, and the direct impingement gas system tends to blow out what might have gotten in after the cover was opened. Conversely, the AK will become a "bolt action" rifle requiring manual cycling to operate, and many other combat rifles will be lucky to get off one or two shots in such tests. Civilian designs generally fare even worse in such tests.

    To make sure that your weapon operates reliability, you should pay attention to what made the original M-16 as tested by ARPA and purchased by the Air Force so reliable, and what made the Army's initial issue so unreliable. The first thing that made the original M-16 reliable was that it had a chromed bolt and bolt carrier. The military changed to a phosphate coating and never went back to a slick bolt and bolt carrier. You are not so limited. Today you can get nitrided bolts and carriers or those with a nickel boron coating and even a few more exotic coatings. 

    Similarly, the original M-16 had a chrome lined barrel. Chrome lining is great because it resists corrosion and wear, but also does so under the extreme temperature caused by prolonged automatic fire. As a civilian, that shouldn't be an issue, so you can go with a chrome lined barrel or select one that has undergone the nitride process. 

    Also, stick to parts made from aluminum and steel at least as good as required by the military. This does not mean that you have to get the most expensive, but you do want to make sure to avoid substandard parts. The primary reliability problems I've seen with ARs has arisen from out-of-spec parts such as an upper and lower receiver that would not properly mate, poor assembly (e.g., a loose gas key), using 5.56 ammo in a rifle chambered for .223 (resulting in primers being popped out the back of the cases after each shot was fired--you can shoot .223 in a 5.56 chamber, but shouldn't try the opposite); and improper buffer weights that led to timing issues. Damaged magazines will also lead to feeding issues, so you should have a sufficient number of magazines to accommodate wastage. 

    Finally, keep your weapon clean and properly lubricated. 

Comparing the .223/5.56 With .308 and 7.62x39:

    One of the primary objections to the AR-15 as a prepper rifle--at least in 5.56/.223--is that the caliber is inadequate for self defense or hunting. The alternatives are generally chambered in .308/7.62 NATO-- such as the FAL, M1A1 (the semi-auto version of the M-14), HK91, or AR-10--or 7.62x39mm as used by the ever popular AK style rifles. First we will look at the hard numbers, and then we will consider the more nebulous matter of terminal performance.

    Sniper Country has put together a couple articles comparing the .223 with the .308 and the 5.56 with the 7.62x39mm which I will use for comparing the hard numbers. Note that the authors of these respective articles used a different mix of ammunition for the .223/5.56 with differing bullet weights, and may have used different barrel lengths as well, giving slightly different numbers between .223 and 5.56. I will include both below. Key points are as follows:

• The bullet weights for the .223 varied between 40 grains at the low end and 75 grains at the upper end; the 5.56 bullet weights were between 55 and 77 grain.
• The bullet weights for the 7.62x39 were 122 or 123 grains.
• The bullet weights for the .308 were between 150 and 180 grains. I would note that standard military ball ammo for 7.62 NATO uses a 147 grain bullet.
• Average velocity from the muzzle to 500 yards were as follows:

AverageVelocity (FPS)	.223 Rem.	5.56 NATO	7.62x39mm	.308 Win.
Muzzle	3189	2989.6	2352.9	2733
100 yards	2795	2664.5	2048.3	2521.5
200 yards	2426	2363	1748.5	2320
300 yards	2088.5	2083.4	1520.2	2182
400 yards	1781.5	1826.9	1308	1946.5
500 yards	1515.2	1572.6	1144	1775

• Average Drop:

Average Bullet Drop (Inches)	.223 Rem.	5.56 NATO	7.62x39mm	.308 Win.
50 yards	-0.26	-0.207	.16	-0.125
100 yards	0	0	0	0
200 yards	-3	-3.38	-6.3	-4
300 yards	-12	-12.86	-25.2	-14.5
400 yards	-29	-30.1	-58.5	-32.8

• Average Recoil (ft-lbs): .308 = 22.5; 7.62x39 = 8.73; 5.56 = 5.21; .223 = 4.29

    Turning to terminal ballistics, I've already mentioned the results that the military saw in early testing in Vietnam and subsequent looks at this subject. But for this part, I will turn to Terminal Ballistics Research which has actually documented rifles and ammunition for use for hunting various sizes and types of game. The selection of bullets is important for effectively taking game. But for purposes of my comparison here, I am assuming that as a prepper you will be stockpiling large quantities of ammunition and, for that reason, will tend toward military surplus or plinking FMJ ammo or inexpensive soft-point ammunition rather than the premium hunting bullets.

    So with that in mind, here is what TBR has to say about the .223/5.56 using FMJ ammo:

    As a varmint or target shooting cartridge, the .223 is an outstanding performer, inexpensive and capable of great accuracy. As a medium game cartridge, the .223 is under powered if fast killing is to be expected with ordinary chest shots. The one exception is when using tumbling FMJ ammunition which completely and utterly changes the performance of this cartridge on medium game.

 

    The tumbling 55 grain bullet is truly violent and fast killing and is the most effective medium game hunting load for the .223. Exit wounds on medium game are often as wide as 3”. However, it must be stated that when full metal jacket ammunition tumbles, the bullet also very gradually falls to pieces due to the unsealed base of the bullet allowing jacket core separation. Because the process is gradual, wounding occurs through vitals and bone, rather than on impact resulting in adequate penetration for all but tail on shots on medium game. 

    The author does not discuss FMJ .308, but here is what TBR has to say about the .308:

Loaded with conventional soft point bullets, many bullet brands lose the ability to produce hydrostatic shock at impact velocities below 2600fps and in such cases, dead running game can be a common occurrence when using the .308 at ranges beyond 50 yards. In fact with some bullet brands, its as if a magic button has been switched off right at the 2600fps mark. Several bullet brands do however have the ability to  produce hydrostatic shock (instant collapse) of game down to velocities as low as 2400fps, depending on target resistance and relevant factors. Regardless, hunters can manipulate speed of killing by matching bullet construction to the job at hand and in this caliber, there are some excellent options, capable of extremely fast killing via wide wounding. The 2600fps parameter and the gradual reduction in shock with conventional SP bullets below this velocity is common throughout the small bores, up to the .338 caliber.

And a warning about using commercial ammunition in military rifles:

Although military ammunition works well in sporting rifles, using sporting ammunition in military rifles is usually not recommended. 7.62 NATO ammunition is loaded to a maximum average pressure of 50,000psi and proof tested at 67,000psi. For reliable feeding in the field, military 7.62 NATO rifles have over sized chambers and military brass is made thick to allow expansion to the chamber walls without cases splitting.  Sporting .308 ammunition is made to the same sized outside dimensions as 7.62 NATO ammunition but lacks the thickness of brass to flow and fill a loose military chamber with the possibility of split or ruptured cases as a result. Commercial hunting ammunition can be loaded up to 62,000psi. Incidents of sporting ammunition rupturing in military rifles are rare, considering commercial ammunition is not usually loaded to high pressures, but incidents have been recorded.

The author does note that the .308 can reliably take game out to 600 yards, but it requires matching the bullet to the game and the distance--i.e., not your standard FMJ or simple soft-point.

    Finally, as to the 7.62x39mm:

    As a hunting cartridge, the M43 round is adequate for close range hunting of lighter medium game but it’s performance is generally poor to fair. Using either military FMJ or commercial sporting ammunition, kills with a chest shot are often delayed while animals shot beyond 200 yards may show no sign of being hit, in extreme cases going so far as to continue grazing (in a confused state) after moving to safer cover. 

 

    Full metal Jacket ammunition generally produces pin hole wounding unless bone is struck. Fast kills can therefore only be obtained with select shot placement. 

 

    Loaded with soft point (expanding) bullets, the 7.62x39 produces somewhat better performance but due to a combination of low muzzle velocities and low BC’s, bullet expansion is limited, the cartridge quickly losing the ability to create disproportionate to caliber wounding. At around 100 yards, width of wounding begins to taper dramatically. At around 200 yards, most soft point bullets have lost the ability to create fast killing wounds. Beyond 200 yards, retained energy is extremely low along with excessive wind drift. As suggested, the 7.62x39 is best suited to the hunting of lighter medium game at close ranges.

In short, when considering inexpensive FMJ or soft point ammunition suitable to stockpiling, the .223 is going to equal or exceed the terminal performance of .308 and 7.62x39 at typical engagement or hunting distances. If you've stashed away some high performance hunting ammunition, the .308 will outperform the .223, however. The trajectory of the .223/5.56 is similar to the .308, but the 7.62x39 drops so much that taking an accurate shot much beyond 200 yards will be problematic. Finally, the recoil is substantially lower for the AR versus the 7.62x39 let alone the .308. 

A Note On Barrel Twist Rate:

    One of the oddities of the AR-15 and the .223/5.56 cartridge is the wide range of twist rates for the barrel. As you know, the rifling in a gun barrel imparts spin to the bullet that serves to stabilize the bullet in flight and make it fly more accurately--similar to throwing a football. 

    The spin is expressed by the twist rate: the ratio of home many turns the bullet makes in a number of inches (e.g., 1:7 would be one complete turn in 7 inches). The ideal--or acceptable--twist rate to stabilize a bullet in flight depends on the length of the bullet relative to the diameter of the bullet. For a given diameter, a longer bullet needs a faster twist rate than a shorter bullet. If a bullet is not properly stabilized it can result in an erratic flight leading to poor accuracy. Conversely, if the bullet is spun too fast, depending on the construction of the bullet, the bullet could disintegrate in flight. Since most bullets are made of copper and lead, the weight of the bullet is often used as a handy shortcut for comparing the length of respective cartridges. So, a recommended twist rate is generally paired with a range of bullet weights.

    The AR-15 as first designed was intended to shoot a short, lightweight bullet of 50 grains at a very high velocity, and so the twist rate was set at a comparatively sedate 1:14. The Army settled on a 55 grain bullet (M193), and while the 1:14 twist rate was fine in most conditions, it was found that it was too slow to stabilize the bullet when shooting in very cold air such as found in Arctic conditions. Thus, the twist was increased to 1:12. This is the twist rate employed in the M16A1 used in Vietnam and up to the early 1980s. 

    Subsequently, the military went to heavier bullet of 62 grains using a steel penetrator (SS109 aka M855). Since steel is less dense than lead, the bullet was even longer than the weight would indicate. After some testing, the military settled on a very fast twist rate of 1:7. 

    Meanwhile, in the civilian realm, shooters wanted to be able to shoot common, inexpensive military surplus ammunition whether 55 grain or the longer 62 grain. Thus, companies began offering rifles using a 1:9 twist as compromise. Further testing and experience showed that 1:8 worked very well in heavier target loads favored by competitive shooters.

    What this boils down to is that 1:12 barrels are best used for bullets of 55 grains or less. Twist rates of 1:9 are versatile and will generally work will with bullet weights from 55 to 68 grains, including the long for weight SS109. The 1:8 works well with bullets up to 80 grains. The 1:7 can stabilize bullets up to 90 grains--longer than will work in an AR-15 magazine or magazine well. It seems to do a better job of stabilizing the heavier bullets out of shorter barrels. Thus, a 1:9 is the most versatile and the 1:7 is probably best for a shorter barrel weapon or if you are shooting the SS109 rounds or 70+ grain bullets favored for their terminal performance. 

    Barrels with twist rates of 1:12 are rare today, and 1:14 is even rarer for the AR-15, but a 1:12 or a 1:14 paired with a 52 or 55 grain bullet at high velocity may provide the best terminal performance out of a simple FMJ bullet like the M193. But the 1:9 or 1:7 may be the best choice if you think you will be using a wide range of ammunition with varying bullet weights or have stocked up on SS109.

In Conclusion:

    The AR-15 provides a lightweight, handy, low-recoiling rifle suitable for use by most anyone old enough to shoot. When using FMJ its lethality will equal or exceed FMJ or even inexpensive soft-point cartridges in larger calibers. It is effective out to distances you are most likely to engage a target, whether hunting or fighting. If properly assembled and lubricated, it is more reliable than most any rifle in the world. It is easily maintained, repaired, or modified. And finally, in 5.56, it uses one of the most common cartridges to be found in the United States.