A buddy called today asking if I could take a look at an AR for him. Seems it was having a feed problem, it was trying to chamber the new round and the spent casing at the same time.
Checked it out and took it apart to look at what might be the issue. Just built so all the parts were new and he thought it might be break in issue. Swapped out a couple pieces and still had the jam issue. I finally pulled the bolt carrier from one of my rifle and a full mag dump later it ran like a top.
Put his bolt back in and fired one round and found the shell was sitting on top of the empty mag with the bolt locked to the rear. Well this means one of two things, extractor or ejector. The ejector was good and tight with good force on the spring so I swapped the extractor and ran another half of a mag without a hiccup.
Couldn't see anything on the extractor, the hook was intact and not broken but for some reason it wasn't holding the shell completely during extraction.
Love it when I get to fix them right for folks.