300BLK cas thickness problems

Hi there
Ive bought some pre formed brass made from mixed .223 ...
I have found most chamber good as gold once primed/powder/pill but.... but some once the pill is seated will no longer chamber correctly and force is needed to eject round ....ive chambered the empty case,it chambers and ejects fine ...load a pill into it and it will no longer chamber properly nor eject
From what ive been reading it may come down to diff thickness in the brass ....
Im trying to find a way to make the neck smaller ... is there a die that I can use to alter the neck ? ... Ive been reading about Reaming .. but im kinda going around in circles trying to look into that one ...
If anyone has any ideas including where to source from please let me know

Sean

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.

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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.

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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

Hi Seano.
Read this document.
STICKY - Good/Bad brass list converting 5.56->300blk - 300BlkTalk
Put the brass that does not work in the bin. I don't know anyone that reams the brass. Its just not worth it.
Buy yourself a Sheridan case gauge. This will pick up the issue once you seat the bullet. Normal case gauges that only check the shoulder and length of the case wont.
Sheridan Engineering - Ammunition Gauges

Good luck.

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.