One of the great debates in the prepper community is the efficacy of high velocity .22 caliber bullets versus slower, but heavier .30 caliber bullets.
Ultimately, a rifle, handgun or shotgun is merely a device for delivering one or more projectiles to a target. There are basically four (4) cartridges used for modern battle rifles: (i) 7.62 x 51 mm (7.62 NATO or .308 Winchester), (ii) 5.56 x 45 mm (5.56 NATO or .223 Remington),1 (iii) 7.62 x 39 mm and (iv) 5.45 x 39 mm. As their designation indicates, the former two rounds were developed and adopted by the United States and other Western nations, whereas the latter two round were developed by the Soviet Union and may be found throughout the former East-Bloc countries and the third world.2
The primary concern when selecting a bullet is lethality. The common assumption is that a larger caliber, more powerful round is deadlier. In his book, Testing the War Weapons, author Timothy J. Mullin summed up this sentiment when he decried the smaller cartridges of the modern assault rifle as ineffective, stating: "I do not believe we need to take bear cartridges to war, but we do need to take white-tail cartridges, at least."3 Unfortunately, it is not as simple as that.
A bullet kills by destroying tissue and causing a sudden loss of blood and, thus, blood pressure. High-power rifle rounds can, in addition, destroy tissue through what is termed hydrostatic shock—essentially a pressure wave created by the transfer of energy from the bullet to surrounding tissue or liquids.4 Bullets intended for hunting are designed to expand ("mushroom") to both create a larger wound channel and transfer more energy to the target, ideally without exiting the target.5 Military rifles, however, do not use the soft-nose bullets developed for hunting, but a bullet fully encased in a metal jacket that can pass through a human body with little or no deformation.6 This means that a FMJ bullet can strike a person and exit the other side leaving only a small, and potentially ineffective, wound channel and no hydrostatic shock.
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.7 At that time, the Army tested the effectiveness of three different calibers (the .30-06, 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. After the Korean War, the Army again revisited the issue, and again found that “at the shorter ranges typical of the modern battle-field, a light, small-caliber, high-velocity bullet provided an equal or better rate of lethality than the hallowed .30—but with far less recoil.”8 At that time, the Army study concluded that the ideal round would use a 50-grain .22 caliber bullet with a velocity of 3,500 feet per second (essentially describing the then-as-yet future .223 round originally used in the AR-15/M-16 rifle). In 1961, the Advanced Research Projects Agency sent several AR-15s to Vietnam for testing by Special Forces.9 The results were spectacular, with gaping wounds and the heads or appendages blown off of some victims. At short ranges, the .223 round was far more lethal than the .30 caliber NATO round. (Although there is some debate that these results were exaggerated or falsified, they actually appear to have been the result of using firearms with extremely low twist rates resulting in the bullets being very unstable when they struck their targets).
This comparison between a heavier .30 caliber bullet and the lightweight .223 round has been confirmed by experience. Alexander Rose has noted:
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 [the shorter version of the M-16 using the .223/5.56 NATO round]. 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.Presumably, the 5.45 x 39 mm is comparable in its terminal performance.
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.10
After reading the foregoing, you might think that I'm recommending one round over the other. I'm not. Rather, I'm offering up for consideration that there is more to the issue of what round to select than "bigger is better."
One of the other factors is the anticipated engagement range. As noted above, as the distance increased, the difference in lethality converged and, in fact, the heavier bullet will retain its killing power well beyond the capabilities of the smaller rounds. Other factors that come into play at longer ranges is the impact of wind on the bullet--the heavier bullet is less effected by a cross wind than a smaller lighter bullet.
So, what is the expected range of engagement? World War II and the Korean War revealed that most small arms engagements occurred at ranges of 300 yards or less. In Vietnam, the engagement range for the enemy was usually fifty to three hundred meters--well within the range of the M-16. However, in a desert environment, engagement ranges may start at 1,500 meters, which is beyond the effective range of the 7.62 NATO.
In other words, in forested or urban (i.e., built-up) environments where there exists a great deal of concealment and obstacles, combat will occur at relatively short ranges. Moreover, in dense underbrush or when inside buildings, a short, handier weapon will be superior. On the other hand, in desert, scrub-land or similar environments where there is good visibility for long distances, combat will be at longer ranges and correspondingly require weapons and ammunition effective at longer ranges. Because there are fewer physical obstructions to interfere with the deployment and use of the rifle, longer rifles are not an impediment, and may be an advantage as far as long range accuracy and power.
1There are slight differences in the dimensions between military (or metric) 5.56 NATO and civilian .223 which could result in feeding problems or mechanical malfunction. Similarly, civilian .308 ammunition uses a thinner walled case that may not stand up to the rigors of the semi-automatic action of some battle rifles.
2 Obviously, there are many other military cartridges that have been developed, including the U.S. .30-06, the Russian 7.62 x 54 mm, the .303 British, and the Mauser 8 mm, to name a few. However, these cartridges are not used in modern combat rifles (with the sole exception of the Russian Dragunov sniper rifle). Moreover, these calibers, and many of the other WWI and WWII military cartridges, are similar in power and performance to the 7.62 NATO round.
3Timothy J. Mullin, Testing the War Weapons, p. 410 (1997).
4 Hydrostatic shock can literally blow apart a can or jug filled with water and, from a high-power rifle such as the .308, smash a board or plank underneath.
5Hollow-point handgun bullets similarly are designed to mushroom when striking flesh.
6 There are several reasons the military uses full-metal jacketed (FMJ) bullets: (i) international law requires it; (ii) FMJ bullets feed more reliably, particularly in semi-automatic and automatic weapons; (iii) the FMJ bullet is less likely to be damaged by poor handling or mishap; and (iv) it has better penetration against barriers.
7See Alexander Rose, American Rifle (2008), p. 299; Julian S. Hatcher, Hatcher's Notebook (1962), p. 44.
8Rose, p. 337.
9Rose, p. 373-376.
10Rose, pp. 403-404. The author has spoken to an Army medic that served in Iraq who similarly related that the 5.56 mm NATO round was much more lethal than the 7.62 x 39 mm round both immediately, and after being shot. Conversely, he indicated that, in his experience, if a person was not immediately killed by the 7.62 round, he would likely recover.