Thread: 300BLK cas thickness problems

From what I have read because the brass is thicker in the body of the 223 brass when it is resized to blackout dimensions it creates a neck that is potentially too thick. Neck turning(skimming the outside of the neck with a "mini lathe") should solve this but take care not to reduce the neck thickness too much as with semi fire the bullet can get seated back too far with recoil if the neck tension is minimal. Cheers.

Originally Posted by Bugbait

From what I have read because the brass is thicker in the body of the 223 brass when it is resized to blackout dimensions it creates a neck that is potentially too thick. Neck turning(skimming the outside of the neck with a "mini lathe") should solve this but take care not to reduce the neck thickness too much as with semi fire the bullet can get seated back too far with recoil if the neck tension is minimal. Cheers.

I made 100-150 from random .223 brass ages ago & found only one brand of military brass caused an issue, the rest were fine, I neck turned them & was GTG

The Blackout/AAC is different to the 300 Whisper in that the chamber neck diameter is bigger to accommodate the brass being made from .223, which was how it was designed to work

Buy the slotted version so you can see what the issue is.
Sheridan Engineering - Slotted Ammunition Gauges

One of the best things I have bought. If the round fits in this, it will work in your rifle.