Why do ARs fail?

The AR15 was and is the most technically advanced autoloading rifle ever designed. It solved a host of mechanical drawbacks that existed in most autoloading rifles, both then and now. The one we’re concerned with is the large bolt rotation angle in rotating bolt designs like the M14 and AK47. Most designs used two lug bolts, which required long cam paths and a lot of time to unlock, which equals no es bueno for a bunch of complicated sciency reasons.

The AR15 solved this problem by borrowing from the Johnson rifle and adding more lugs. The bolt didn’t have to rotate as much to unlock, meaning it could unlock faster because the carrier didn’t have to travel as far, leading to greater accuracy and reliability. And to cartridges with higher chamber pressures, enabling the poking of small holes in Russian helmets at greater distances (raise your hand if you ever dreamed THAT would be relevant again in the 21st century).

The downside is that the lugs were more delicate. This wasn’t a problem with Armalite’s AR15, or the numerous M16 variants that were put into service for the duration of the Cold War. It was, however, a problem with shorter variants that started popping up in the Vietnam war. However, these sawed-off variants weren’t especially prized at the time, at least not outside of certain skydiving clubs, and M16 bolt carrier groups would outlast the barrel. Several barrels, actually…by which time the receivers themselves would be toast. In other words, the M16 would outlast any other assault rifle at the time by about a factor of four, and the bolt carrier group wasn’t even the weak link. Thus, improving it was an answer to a question that almost nobody was asking.

Moving past the Cold War, though, two things happened. First of all, people got too lazy to march into battle, and, well…it’s very awkward getting into a car with a twenty inch barrel. Pretty soon, though, the problem got even worse. People couldn’t even be bothered to go outside to fight wars anymore, preferring instead to fight from their living rooms (and thus was born urban warfare). And if you think twenty inch barrels were inconvenient for getting in and out of cars, just imagine trying to conduct combat maneuvers inside the confines of someone’s living room.

Obviously, the niche sawed-off variants of the Vietnam war started looking a little more attractive. And as things got progressively shorter, the old problems started rearing their heads again, in the form of broken bolts and cam pins.

As these guns were widely fielded, it became apparent that the breakages could be unpredictable and random, occurring at any round count, despite preventative maintenance. The industry immediately set about designing a better mousetrap, and this became the LMT enhanced BCGs that were later further refined by KAC as the SR15. While these solved some hitherto unrealized design flaws with the AR15 bolt, namely the counterproductive lug opposite the extractor, they were expensive as all getout, and not at all backwards compatible with legacy weapons.

While all that was happening, though, incremental improvements were being made by Colt with the existing BCG, mostly in the form of better quality control and refining the heat treat method. This resulted in a few minor tweaks to the TDP, which produced a milspec bolt that could reliably outlast any barrel. See, barrel life goes down exponentially with length. A twenty inch barrel could last fifty thousand rounds, while a ten inch barrel was pretty well cooked at a mere six thousand. Barrel swaps typically necessitate bolt swaps regardless, and thus the enhanced bolts were never put into service.

This isn’t to say that unpredictable failures were stopped altogether, as evidenced by the fact that many Special Forces units still require the carrying of spare BCGs in the field. The failure rate was just reduced to the point that adopting a new AR variant wasn’t seen as a good use of funds, especially given that the AR15 platform and 5.56 NATO cartridge were already looking to be replaced by that time.

Fast forward twenty years later, though, and the AR15 is still the dominant issued platform for all of NATO, with no end in sight, in its 5.56 NATO chambering no less. And attempts to find a new standard has resulted in a proverbial herd of cats, with every NATO member and its units all pulling in different directions. The SCAR, HK416 and now the XM5.

Worse yet, the commercial market has also yielded to sub sixteen inch variants being the norm, with bolts of varying-but mostly dodgy-origins. And because of stuff and things, those dodgy commercial variants are now being widely fielded by, shall we say, NATO adjacent organizations.

And even if the AR15 is usurped as NATO’s main squeeze, this process will be slow, and support units and NATO allies will be inundated with used-up hand-me-down Mk18s that might be a warm day away from shearing a bolt lug, especially since they’ll probably come with the new extra spicy M855A1 cartridges that replaced the standard pressure M855. It was really nice of the Army to leave us that little treat right before leaving the party, huh?

American civilians will be in the same boat. While M855A1 isn’t common on the commercial market YET, there’s nothing legally preventing M855A1 from being sold commercially, and while certain political forces don’t want that, economic forces generally prevail. The government likes buying things cheap, in quantities from approximately one to one gazillion, to be determined by the declaration, or lack thereof, of WWIII. In other words, the manufacturer must produce one gazillion units with the knowledge that there’s a 99.9% probability they will sell only a small fraction to the government, with the rest usually being sold to the American consumer. In a few years, Lake City will be sitting on warehouses full of M855A1 that the government won’t be ordering, and everyone’ll be itching to slap an XM sticker on it and surplus it out to recoup their investment. With the next highest bidder being African warlords, the political forces generally end up conceding that it’s best to let it go to Americans, being that they will safely destroy it by way of dirt berm, rather than using it for other, less politically expedient purposes, such as genocide.

In conclusion, the AR15 BCG problem is not only not going away anytime soon, it’s going to get a lot worse before it ever gets better. And even if you as a soldier or civilian have your rifle squared away, the guy in the trench next to you might not. So you best get used to carrying spare bolt parts, and I humbly submit the ARFAK is by far the best way to do that.