Forward to the Past? The New M5 Carbine

If you haven't already heard, the Army has selected a new infantry carbine (the XM-5) and squad automatic weapon (XM250), both chambered in 6.8x51mm. With the Army also planning on converting the M240 to use the 6.8x51mm, the Army will finally realize its long held dream to have a single cartridge for its small arms. (Except it won't because non-combat soldiers will still be using M4s and, of course, there are those darn 9mm handguns, but let's not spoil the dream).

    The military is being all hush-hush about the performance of the new round. However, Sig has released a civilian version to the market--the .277 Fury--which gives us some insight into the cartridge and its capabilities. As you may have already guessed from the metric dimensions, the .277 Fury is, kinda-sorta, a necked down .308 cartridge, something to keep in mind for further discussion below. But because it operates at chamber pressures of 80,000 psi, Sig had to design a new hybrid case using a stainless steel base that attaches to a brass walled upper. This allows 135 and 140 grain bullets to be launched at 3,000 fps and 2,950 fps, respectively, out of a 16-inch barrel. A 150 grain bullet drops the muzzle velocity to 2,900 fps. Those are impressive numbers for shooting out of a 16-inch test barrel. The cartridge also boasts 6 to 9 feet less bullet drop at 1,000 yards than the 6.5 Creedmoor. And it is all because of the greater chamber pressure. 

    The reason for the new cartridge is supposed to be two-fold: (i) it provides a greater effective range--some 300 meters more than the effective range of the standard infantry rounds used by the Russians and the Chinese--and (ii) it is supposed to offer greater penetration against the body armor expected to be fielded by Russian troops (but which don't seem to have been used--at least to any great degree--in the Ukrainian conflict) and the Chinese military.

    The greater effective range, of course, is dependent on soldiers being able to see and accurately target their enemies on the battlefield. Otherwise, all that extra power is wasted. To this end, the military will also be outfitting the rifles with a new optic system: the XM157 Next Generation Fire Control System. This is a 1-8x LPVO that, while it uses an etched reticle in case the battery dies or the electronics are damaged, is able to correct for windage, angle and distance for different projectiles and project a corresponding targeting dot. In addition, it can share information between members of a unit so that if one soldier is able to tag a target with the system, that information can be shared with other soldiers (or, I'm sure, overhead drones, guided munitions, etc.--you get the idea). Using this system, every infantryman will, in theory, be an expert marksman. 

    While the greater effective range is believable (provided the XM157 works as intended), I have my doubts about the increased effectiveness against body armor. It is well known that bullet penetration of body armor is mostly dependent on velocity, and the magic velocity for Level IV is about 4,000 fps for standard copper jacketed bullets: well above the muzzle velocity of the new 6.8x51 cartridge. That means that the military is going to be relying instead on special penetrator rounds to achieve penetration at a lower velocity. But how much lower? And how expensive will be those rounds? 

    So, those are the upsides to the system. What about the downsides? The video from the military arms channel embedded below discusses the probably downsides in detail and I suggest you watch it if you have the time.

VIDEO: "Goody bye M16! Military Adopts the M5 rifle and 6.8x51. Are they crazy?" (39 min.)

If you don't have time, here are the highlights:

• It weighs more than the current M4. Much more. The bare bone XM5--no suppressor or sights--is 8.38 pounds (vs. 6.43 lbs for the stripped M4). With the suppressor that is supposed to be used with each rifle, the weight goes up to 9.84 pounds. Vortex hasn't released information on the weight of the XM157 optic, but for comparison a basic Vortex Strike Eagle 1-8 LPVO is 17.6 ounces. With the extra electronics on the XM157, I think that doubling of that weight is probably not unreasonable, so about 2.3 pounds. In other words, the Army's new rifle, in its standard configuration, will probably be running about 11 pounds or so. By comparison, the M14 was only 9.2 lbs., and it was considered to be too heavy.
• The high chamber pressures will wear out barrels very quickly. Which means frequent barrel changes, especially if the military brass expects those rifles to actually still be accurate out to 800+ yards.
• Although it is not known what will be the magazine capacity selected by the Army--20 or 25 rounds--it will be less than the 30-rounds standard for the M16/M4 or Chinese or Russian weapons.
• The Army touts that the cartridge weighs less than the .308, but it weighs more (a lot more) than the 5.56. So soldiers will not be able to carry as much ammunition. I can't find specifics on the cartridge weight, but the design is supposed to be 20% less than a similar sized brass cartridge.
• The recoil is supposed to be less than a .308, but probably not much less. If you watch the video above, they have clips of various people shooting the weapon; and it is readily apparent from those clips that the recoil is substantial and that the weapon will be uncontrollable in full auto. Yes, I know that all rifles are uncontrollable in full auto to one extent or another, but this appears to be in line with M14 or FAL uncontrollable. And check out the fool that tried shooting it with the butt high on the shoulder like you can get away with using a 5.56. With this new rifle and cartridge, we will probably see the return of the much derided "chicken wing" as soldiers learn to lift their elbow a bit to create a better pocket in which to tuck the butt of the rifle. 

The recoil may, in the end, spell the doom of the new cartridge. As discussed in the video, the higher recoil will likely result in lower qualification scores, particularly among smaller soldiers (e.g., female recruits), which could result in something similar to what we saw with the FBI's adoption of the 10mm. That is, the FBI believed that the 9mm was inadequate and so it adopted the 10mm. It then  saw qualification scores fall off due to the size and recoil of the new cartridge, switched to a lower power 10mm to compensate, then to the .40 S&W since there was no longer the need for the longer 10mm case, and then when it was apparent the .40 S&W was not any better than the 9mm in any practical sense, returned to the 9mm. 

    My own thoughts are somewhat mixed as to the rifle and cartridge. On the one hand, I just put together a lightweight AR10 in .308 with a 16-inch barrel to serve as a modernized version or interpretation of the Scout Rifle concept (although mine is much lighter than the M5), the idea being to have a sort-of "do it all" rifle that could be used for hunting but pressed into duty as a defensive rifle if need be. So I can understand wanting a rifle that can reach out and touch someone at longer distances.

    On the other hand, it is hard not to draw comparisons between this rifle and cartridge combination and the decision making that led to the adoption of the M14. The M14 was the product of military brass wanting to simplify logistics by having a rifle and cartridge that could do everything (and do it out to five or six hundred yards), but produced a rifle that was too heavy and had too much recoil to be useful for the common infantryman. 

    More than the problems inherent with using a high pressure round and the issue of recoil, I believe that what will make or break this project is the weight of the weapon and the ammunition. I have to wonder if there is not some exo-skeleton system out there that the Army also plans on adopting.