The dreaded do-nut, I ask questions like, it is stretch? Is it flow? is it both stretch and flow.
I make do-nuts, I have dies that are do-nut making machines without firing the case, there was a smith that was happy with 60% failure rate when fire forming cases. The chamber was a 22 Improved 6mm Remington.
To help him out I formed the cases from 25/06 and 30/06 cases for added length between the shoulder and case head. By the time I got the cases down to 243 the neck was almost closed off meaning I had to ream the necks. I had to ream the necks again when the cases were necked to 22 cal.
Then there is the shooting of the case and creating donuts, there are many links posted about bench resters, not new information but information that has been around for 20 to 30 years. Without fail the do-nut comes up, goes something like "don't worry about it, it happens" (reminds me of Forest Gump). the do-nut is a restriction, something like an orifice in a line to control flow, then there is that part that goes something like 'don't worry about it, if the bullet does not come in contact with it when seating apply the leaver policy, leaver where you founded. Then there is push it out to the outside then trim the neck.
F. Guffey BRtB