I'm having failure to extract problems with one of my carbine uppers. I've tried multiple bolts and the problem persists.
Four different types of ammo:
Barnul 62 gr steel case -- No Problems
XM193 -- No problems
M855 -- No problems
South African -- FTEs after every few rounds
Different magazines make no difference. The same lot of SA runs fine in a couple other guns.
Any ideas?