OK, my guess, try a standard BGC. Side chargers use a bolt screwed into the front of the BGC and if too deep, would prevent the bolt from moving in the carrier. Second, check the tail of the bolt! It is the back seal of the 'cylinder'. Leakage there and no worky. The rings are the front seal. 147 gr @ 2k fps is a pretty hot load. Would work fine in my 16" carbine. Other thing to check is the length of the spring. Can you easily lock back the bolt, in the gun? GK had a 308 with a too long spring, wouldn't cycle properly - almost had to use 2 hands to lock it back as the spring got wonky and bottomed in the tube. Cut off a couple turns to make it fit. Of course the normal staking gas key check and length of the tube into the key. Use a pipe cleaner to check the key isn't clogged - I did have that problem once. Heavy buffer is to slow down bolt speed so it locks back. I use a heavy weight in a 10" pistol port BO. I've not used anything but 'proper' standard spring in any of my ARs.