#Sixtyforce cartridges mod#

And some have both, such as the old loading, the M-193, the 55-grain load from the Vietnam era. Lots of bullets overturn, tumble in the parlance, and lots of bullets have cannelures. When it begins to overturn on impact, it then breaks apart at the cannelure.

The cannelure is a place to crimp the case neck into, but it also strategically weakens the bullet.

#Sixtyforce cartridges mod#

The next step was a refinement, the Mk 262 Mod 1, which included a cannelure in the bullet. The longer bullet is less stable than the shorter, 62-grain M855, and thus overturns on impact or soon after. What it does is simple: it takes advantage of the too-fast twist of the M16A2 and M4, the 1:7 twist, and loads a 75- or 77-grain bullet in the case. As a result, the now well-known Mk 262 load was developed. This time, they came back too often, and too frequently, and over a long period of time, to be ignored. So the system stayed quiet until we were in another shooting war, and reports came back. To everyone’s surprise, small bore ammo designed to penetrate to a fare-thee-well failed to do more than create simple perforation wounds on unarmored opponents. There, good shooters (Rangers, Special Forces and Delta operators) spent a long time, and a lot of ammo, shooting at people who in many instances didn’t fall down when hit. I had a talk with Mark Westrom, CEO of Armalite about that, and he remarked that it would cost more to prove to the Army that a 1:9 twist was better than it would cost to re-barrel every rifle in inventory to 1:9.įast-forward to Somalia, the infamous “Blackhawk down” incident. Only the tracer really needed the new twist, but the military approach was/is a “one size fits all” approach, so there it was. The new rifle also received a new barrel twist, one turn in seven inches, to fully stabilize the SS109 and the tracer as well. So, the push was for armor-piercing performance, leading to the SS109 and the later M-855, with a 10-grain steel penetrator tip inside. They expected to face lots of targets, and not only armed ones, but armored infantry. Seriously, the expectation was that the Soviets would roll West, and the NATO allies would be faced with Russian, East German, Polish and who knows who else mechanized infantry piling out of their BMDs, BMPs, and BTRs, lining up and assaulting the NATO positions. What, there never were swarms of Soviet infantry in Western Europe? Musta worked. That was intended for use against swarms of Soviet infantry in Western Europe. The special got stretched and boosted, until the 55-grain FMJ was at 3,100 fps.Īnd there it stood, until the mid-1980s, when the SS109 came about. Finally, they insisted that the bullet used had to penetrate a steel helmet at a distance farther than their own research had indicated soldiers fired on opponents. The Army, trying to keep the AR away and keep the M14 in the running, kept moving the goalposts. 222 Special delivered the kind of performance that the designers wanted, which was basically a 50-grain bullet at under 3,000 feet per second. 223/5.56, it was a slightly smaller cartridge. The original caliber for the AR-15 wasn’t the. Patrick Sweeney takes a new look at this 1960’s wildcat for the AR platform in his 2010 book The Gun Digest Book of The AR-15 Volume 3.