For the last year I have owned a DPMS Chromlined 16inch Carbine upper mounted to a firebird lower. Parts kit is DPMS. About 8,000 rounds through the rifle. Not a single issue until I hit about 7,400 rounds. Suddenly, after thousands of rounds of steel case, it has begun short stroking with both TULA, and WP (happens less with wolf). Removed ST2 buffer in lieu of a carbine buffer and now it happens less, but still occurs. Problems do not occur with high pressure NATO ammo. Leads me to believe I may have an issue with the gas rings or the gas tube. The mushroom on the gas tube appears to be gone. Carrier is well staked. Is not a full auto carrier. Bolt does not fall out under gravity. Parts added when I first got the rifle: Gunfighter MOD3 charging handle, ST2 Buffer, EOTECH XPS2, Daniel Defence EZ CAR, Houge grip, Vortex FlashHider. Using a variety of mags, happens with all of them. PMAGS, USGI with magpul follower and LANCERs. I keep the rifle very clean and well lubed with MOBILE 1. Any Advice (besides dumping it and buying a COLT/LMT/DD/BCM.)?