here are some pics that show the big difference in strength between standard grade steel and ar500. The roundplate ar500 is 3/8" thick and the rectangle standard grade is 1/2" thick. They were set up at 100yards and shot at with my ar15 in 5.56/.223 and a guys 7.62/.308 ar10 variant. The .308 and .223 are indistinguishable when shot at the ar500 but you see the difference in the standard grade. The .223 just nicks the steel while the .308 craters it deeply. If you can get multiple shots in a concentrated area you could definitely pierce the 1/2" plate.