Quote Originally Posted by mack7.62 View Post
The question is will it penetrate SAPI and ESAPI.
Even an old delaminated SAPI plate is likely to take an entire magazine of M855 to get pass throughs. If I remember right, a SAPI plate can actually take an M2 AP without pass through but fails the back face deformation and therefore can't be level iv rated. Honestly, there's not much out there that's available to us civilian types that can defeat milspec armor, and for that matter I don't know if even M955 would do it or not.

The same can be said of almost any ceramic based commercial armor, as well, even the cheap brands. You can get ceramic plates for as little as a hundred dollars that will easily defeat almost any rifle round available on the commercial market. This is a growing problem because more and more criminals are turning up with body armor. It's something that hasn't historically been a problem in the past because armor used to be expensive and hard to find, and criminals were rarely confronted by armed victims. That dynamic has been flipped on its head over the last decade, though. Not only are more people armed than ever before, with better weapons than ever before, but now criminals can get extremely effective armor for next to nothing off of Wish. I expect in years to come that "armored robbers" will become the rule rather than the exception.

Now what M855 absolutely CAN defeat is polyethylene armor, which represents a massive market share of cheap commercial armor. One of the caveats to the cheap ceramic based armor is that it's extremely heavy, whereas you can get cheap, ultralight polyethylene armor for under a hundred dollars a plate. While there are a few polyethylene plates that can stop M855, they are around a thousand dollars a plate, so unlikely to be found on your run of the mill bad guy.

Unfortunately, though, almost all AR500 steel armor can easily defeat M855, so no help there. Outside of legit AP rounds, the only thing that can defeat AR500 is something going over about 3k FPS, namely a point blank hit from M193 from a 20 inch barrel. And unfortunately, the cheap, concealable nature of AR500 makes it perhaps the most common commercial armor you're likely to find out there. It's extremely heavy, but your average thug doesn't care about that. What can, however, defeat AR500 is M855A1, at least from a 16" barrel at close range. Hopefully that will become more available going forward, or something similar to it. It's not without its issues, though, besides its expense. It accelerates wear due to the high pressures, and you have to use a special magazine to get it to feed right, and those magazines are said to be garbage. The only ones available on the commercial market are from Center. Allegedly, the ones made by Okay are better, but they're unobtainium at least for right now. I have heard that the third gen pmags will feed M855A1, though, so if you managed to find some then maybe that's a viable solution.