i was unsure what would happen here... i have a "spinner" target and have just used it with .22s. i decided hmmm, what would happen at 10yards with the ar15. well i found out, i was hoping it would blow a hole straight through, that would have been impressive but what it did do is go about 95% through and leave a .45 size hole. im surprised it didnt make it. it DID penetrate the full 1/2 inch but it is bubbled out on the other side.
one of the interesting parts is the bullets jacket is on the outside of the hole, it makes up the "blown out" part.
was hard to get a good pic, this is the best i could do