tight neck

[RWBlue]

Well after forming, trimming ....some 5.56 brass into 300-221 brass, I made some dummy cartridges.

I dropped them in the mag, I release the bolt, I try to extract, I try to extract, I TRY TO EXTRACT, I extract

What do you think, is stiff extraction of dummy round telling me that I can not use formed brass from 5.56?

Am I stuck with 221 Fireball brass?

Do I need to case my chamber?