Hi everybody, I'm working on a new AR15 rifle and have run into a snag with getting it to cycle and lock back.
The cartridge is a 358 Winchester short x 1.71", just short enough to fit an AR15 magazine. I'm loading Hornady 200 FTX to 2471 and Speer 180s to 2599fps with CFE-BLK.
The barrel is from DeadShot Barrels in Oregon, it has a mid length gas system.
They cut the chamber with a standard 358 Win reamer and set the headspace off of a case I sent to them with the bolt.
For loading dies, I just cut about .3" off the base of Lee dies and they seem to be working great.
For brass I'm using Winchester 308 Win once fired cases, cutting them off at the shoulder, then lube and run through the shortened sizing die, then trim to length at 1.71"
My first loads were with 1680. I started with a CAGB adjustable gas block. It came with the gas port drilled to .086" and would not lock the bolt back. I drilled the hole to .096" and now it locked back on the largest setting. I set the gas block back one notch and it wouldn't lock back, so I set it back to all the way open and thought I was good.
I tried some cast loads with the Lee 358-200 and they barely hit the target, so I gave up on that idea for now and went back to jacketed.
During load developement, I decided to switch to CFE-BLK as it's slightly slower burning and I got better velocities.
Now the gun started to not lock back. I went back to 1680 and it still wouldn't lock back on the last round.
I cleaned the inside of the upper and reoiled the BCG, but no change.
I then drilled the gas port to .116", but no change.
I oiled the recoil spring and buffer, no change.
I wondered if maybe part of a gas check got stuck in the gas block, so I replaced it with a standard gas block, no change.
I'm at a max load with CFE-BLK and I'm getting great accuracy and velocity, so I can't load any hotter.
My other thought is to open the gas port even more, but I think something else must be wrong as it used to cycle when I was first breaking it in after the gas port was at .096".
I am open to any and all suggestions.
Thanks
Glenn.