so I just shot my new AR yesterday and it was jamming like crazy. the rounds weren't fully ejecting. the spent cartridge was getting stuck on top of the next round that was on its way in. its a huge pain in the ass to un jam it too. I was thinking it may have been a bad extractor or weak extractor spring (it looked fine when I took it apart) but I also read a post by a guy on some other forum that had the exact same problem and the a factory tech said that some ar's have a 300-400 round break in period? if it helps I have a Stag Arms 6LSuper Varminter and I started off shooting some cheap 55gr (not sure the brand) then switched to Black Hills 75gr match. same problem with both.