Thread: Making 300 Blackout Brass. Neck Diameter Issues.

I learnt something last night which you guys might be interested in if you are making or going to make 300 aac brass from 223 brass.
I have a case gauge but this only checks the head space and the length. It does not check the neck diameter.
Long story short, I ended up with about 100 rounds that wont chamber because the neck diameter is too large. Out with the bullet puller and 10 minutes latter it was time to start again with a different type of brass.
The brass that caused the issue was RG. Changing to FC solved the issue. Neck turning would have solved the issue too but this is way too much work.
This is a good video on the issue I had.
https://www.youtube.com/watch?v=_08yZXnk7ro

In short American sourced brass should be fine. The European brass is likely not suitable to be made into 300 Blackout without a lot of additional work.
Think I might try and buy one of these as they do check the neck diameter.
Sheridan Engineering - Ammunition Gauges