@jwp475:
I used a 5 gallon water jug behind the armor panel so it would have something to hold it in place, but something that would give a little too, like a torso would.
I have since obtained several flat UL rated ballistic fiberglass hard plates in UL stand alone level I, II and III.
In conversations with the owner of the armor company, he said that to stop 5.56mm fire you need to use 3 sheets of the level III (9/16" thick) to defeat M855 green tip. So i expect that probably 2 plates will defeat a hot 5.7mm round, but i've not yet tested it. I did test the Level I (5/16") plate against a 115gr 9mm FMJ round, and the Level I plate stopped it dead cold, without any spalling or back face deformation.
I've not shot anything living with it yet, in the way of game animals, but others have posted numerous videos or photos/accounts of 5.7mm used in this role, and none have reported that it failed to do the job, even against big feral pigs and white tail deer.
I started out a skeptic when it comes to the 5.7mm, but as the data (as opposed to internet rumor and lore) started to come in, it became very clear that the 5.7mm is far, far more than just "a souped up .22 magnum", as many derisively claim.
