Showed up at a match today with my 14.5" upper on my lower off of my BM 20". That lower has a match trigger in it and is all BM other than the trigger and hammer. Had five malfunctions in 40 rounds fired. Empty case is stove piped with a round trying to chamber wedged under it. Bitch to clear. That same upper runs fine on its usual lower that has a Colt A1 stock, buffer, tube and spring. So what's the difference in full length buffers and springs? I don't have a scale to accurately weigh them.
The extractor and ejector look and move fine.
Help!