300blackout build, what you know like and dont

[destrux]

I did find that with my rifle I had to use a lighter than standard buffer weight to get it to cycle with subsonics. I'm running a buffer with two steel weights and one delrin weight. I run an Anderson adjustable gas block so I can crank the gas down for full power ammo.

[Wedgie]

Just found this thread. I built an 8" SBR specifically to run the 225-247 cast bullets, subsonic, through a suppressor. I have tried a lot of plain base bullets with the target velocity of 1050 fps and was disappointed to find that I was getting lead deposits on the muzzle, bolt tail, in the gas key and in the blast chamber of the suppressor. Gas checks solved the problem. It seems that to get 1050 fps out of the 8" barrel the pressure/time exposure of the bullet base causes melting of the bullet base. As the bullet was passing the gas port lead was being forced into the gas system and as it exited the muzzle lead was being deposited there. My rough calculations for the 8" barrel put pressures around 34,000 psi. I have tried powder coated and various degrees of hardness with no luck. Gas checks have been my only solution so far. Any suggestions are appreciated. I have tried A1680, Lil'Gun, and am now running IMR 4227. So far my favorite load has been 9.7 gr of IMR 4227 behind a 225 gr (NOE 311-247 RG GC).

[popper]

I shoot supers PB, cleaned the rifle yesterday, no lead at all in the BCG, ESPC. I suspect gas cutting due to your PB below the neck. GC kinda solves that problem, especially if your using a BT boolit.

[Wedgie]

I had thought of that but the amount of time the bullet is below the neck is so small. I do not get any ablation on the sides of the bullet. But that could be it. What speed, bullet weight and barrel length are your PB loads?