It must have been machine gun brass. I've never had this problem with any other reloading. I've reloaded thousands of pistol and rifle calibers. I measured and trimmed to proper length, ran through two different sizing dies. I've never had this problem with commercial brass.
Would anneling the cases, then sizing them help?
NO...
As said, Small Base Die, or other alternative would be a body die, and do the 1/4 turn camming effect on the brass...
Pocket swager from Dillon...for the military primer crimp.
Then also do neck via a 308 Lee Collet Neck Sizing die.
Simple solution, you just evidently don't have the right dies for the application..
