well I got my first ar-15 today from the local pawn shop. bushmaster xm15-es2 20 inch with scope , bi-pod, etc. I shot about 40 WWB out of it they shot and grouped well. Then I tried some barnual I got from academy. Out of 20 rounds I'de say 7 went "click"  The primer had a normal size dent  in it. I put one back in and it fired the second time.  I've shot plenty of barnual out of my ak's and never had any problems.  I'm thinking weak spring? But the rifle looks fairly new so I dont know, Maybe crappy ammo.

Nice!!!  

Can you normally find AR's at pawn shops?  Never heard of that before

Communist ammo has very, very hard primers. Fortunately, the AR has a pretty stout spring to smack them well. I'd check the firing in protrusion as well as clean out the inside of the bolt, make sure nothing is taking a little bit of the OUMPH out of the strike.


Spring should be fine, but check that too....