05-10-2012, 01:38 AM
LRRPF52 Wrote:Also, regarding the yaw performance percentages, what is the expectation? For a projectile to behave predictably 100% of the time in a mass-produced assault rifle load? We have to establish some expectation guidelines before citing percentages for how many times a certain projectile does X, Y, & Z in ballistic gelatin. 70% consistency seems pretty dang good to me, for a standard AR load. From a soldeir's perspective, I'm not waiting to see what just one round does to an enemy, regardless of what rifle or carbine I'm carrying. They will get at least one follow-up shot at distance, and 3-5 at CQ ranges, unless a head shot drops them like a sack of potatoes before I can make another at distance.
The perfect bullet for terminal effectiveness will begin to yaw as quickly as possible after impact (within 2 inches of penetration), will be travelling sideways through the zone of maximum damage (on average, say 4-8 inches) to create the biggest possible wound channel there, and will penetrate at least 12 inches but no more than 18 (or energy will be lost through overpenetration). Furthermore, it will perform like this every shot, regardless of impact velocity or striking angle.
Of course, no bullet will perform like this 100% of the time, but that provides a benchmark for judging what actually happens. So if 70% of M855 bullets don't even begin to yaw until they have penetrated 4.7 inches, that is bad news. That half of the remainder don't yaw at all is even worse. That leaves just 15% of bullets which do perform well.
I don't have equivalent figures for other bullets, but I do know that the performance of the M855 is considered to be poor. In particular, the need for it to be yawing in the air by at least 3 degrees at the point of impact before it will yaw quickly in a body is significantly worse than other military bullets tested.