About a week ago I took my rifle out to the range. I fired about 50rds through the 223 upper, then switched to my RRA 458 upper. The rifle fired 3 rounds, had one FTFire, fired one round, then would not fire anymore.
When I pulled the trigger I could hear the hammer drop but nothing happened. I checked the primers, no indication of any firing pin strike. The upper was clean (only 20rds down the tube since the last intensive cleaning). I checked the bolt and firing pin for any broken parts, nothing.
I did notice difficulty extracting about half of the unfired rounds (this was also a problem when the upper was new but RRA polished it and it has been fine since). The only things that I can isolate as variables from its previous flawless performance is: use of a standard rifle buffer spring, a mildly dirty lower, and single digit temperatures.
When I got home I completely disassembled the rifle and cleaned it to like new condition and reinstalled the green RRA buffer spring. Friday morning I took the rifle back to the range (still single digit temps here in MI). It fired 3 rounds without a problem. I reloaded the mag and after that it would not fire. Same deal as before. Again about half of the unfired rounds extracted hard, but the chamber seems clean still. Incidentally, I threw the 223 upper on after the 458 gave up. The 223 didn't have a single issue. Could the temp be the cause of the problem? Could this be a bigger issue?
It's gonna be about a week before I can take it out in temperatures over 30.