05-19-2018, 02:18 PM
I have been having a problem on my Grendel build. About half the time when the last round is fired the bolt only partially locks back. Instead of the bolt catch locking on the bolt face it catches on the front of the bolt carrier. Some info on my build: Spikes Tactical Lower, PSA upper, 18" JP barrel with a rifle length gas system (RLGS), adjustable gas block, JP Silent Capture spring with standard spring set.
Some of the things I have done:
Yesterday I was working on my son's Grendel which was running perfectly with the Hornaday Black 123's and tried my reloads. This rifle has a 20" Barrel, a non-adjustable Gas Block, and a standard rifle length buffer system. His rifle started locking back just like mine had been doing so it has something to do with my loads. I am running a Hornaday 123SST over 28.2 Grains of IMR8208XBR in Hornaday cases and a CCI #41 Primer. My MV is averaging 2518 which is close to the 2500 I see out of the Hornaday Black factory ammo. I still think I can get this load functioning if I can just tune my Gas System/Buffer system right. Should I start with the assumption that I am Over or Under Gassed?
Some of the things I have done:
- Gas block was initially set almost closed and opened a half turn at a time looking for where the bolt reliably locked back. I have it pretty well wide open now. I made measurements on where the gas port is and verified alignment.
- I tried the upper on another lower with the same results.
- I have another adjustable gas block from Odin Works on order.
- I just got a spring set from JP for the SCS but I have not tried the other springs yet.
Yesterday I was working on my son's Grendel which was running perfectly with the Hornaday Black 123's and tried my reloads. This rifle has a 20" Barrel, a non-adjustable Gas Block, and a standard rifle length buffer system. His rifle started locking back just like mine had been doing so it has something to do with my loads. I am running a Hornaday 123SST over 28.2 Grains of IMR8208XBR in Hornaday cases and a CCI #41 Primer. My MV is averaging 2518 which is close to the 2500 I see out of the Hornaday Black factory ammo. I still think I can get this load functioning if I can just tune my Gas System/Buffer system right. Should I start with the assumption that I am Over or Under Gassed?