All body armor protection is based on velocity. That velocity depends
on barrel length.
I dunno but I think I'll let someone else break their wrist firing a .223 round out of a snub nose trying to find out.
Recently reviewed stats on 5.56 ammo. In order to generate optimum results, a 20” barrel is the minimum requirement. With most people shooting lesser length barrels, velocity required for penetration (originately considered to be a helmet) is not reached. In my opinion, most shooters of “green tip” ammo purchased it as an alternative to standard loads, not for so called armor piercing ability. This proposal is a back door effort to make 5.56 ammo less available to the public by removing the ability to sell production overruns. As panic buying of green tip ammo took place, there has also been a similar run on standard 55 grain ammo much like we saw in the past. Prices are up and availability down, just what I think this administration wants.
The problem with a short barrel is that there is not enough length to the barrel to stabilize the projectile. The heavier the bullet, and M885 is pretty heavy for a .224 bullet, the longer the barrel that is needed. Also it is the twist of the rifling in the barrel, or twist rate. It's kinda hard to get a lot of rifling in a short barrel. I don't think that 62 grain 5.56 would perform well in such a short barrel. On the other hand, drop down to a 30 grain bullet and increase your velocity and you have the magic required for penetration. It all boils down to kinetic energy, KE = 0.5 x m x v^2. There are other factors involved as well, but the bottom line is you can create better penetrating ammo than M885 with a lighter bullet which is easier to stabilize in shorter barrel.
All body armor protection is based on velocity. That velocity depends
on barrel length.