#5.56mm7.62mm

That seems like a pretty straightforward question, doesn’t it? On the surface, armor piercing ammunition ought to be ammunition that pierces armor, right? Seems pretty simple. Except it isn’t. At least, not according to the BATFE. Under 18 United States code, AP ammo is defined rather arbitrarily as:

In the first two parts of this article on a new long range infantry rifle paradigm, we painted a picture of what sort of weapons would be needed to maximize the infantry’s long-range capability, in theory allowing them to achieve “overmatch” versus enemy infantry armed with existing .22 and .30 caliber weapons. We created estimates for both the cost and weight of the infantry rifle, and we also examined the problem of training soldiers to maximize their capabilities with the new longer-ranged weapons.