New RCBS, all measures correct! I don’t lube the inside of any cartridge, I use anhydrous lanolin on the shell, I believe I may have had it set to deep? Not sure why it only did that to one out of 8. Thanks for advice.Do you chamfer the neck mouth?
Are you lubing the necks or the expander ball or both?
Is the expander ball too small?
It's possible that the expander ball may need to be polished a little bit. Crocus cloth while the expander is spinning.
This is just a couple of the dozens of suggestions which could be made considering your situation.
Check and measure everything.
You were correctSounds to me like you seating die is set too deep causing the brass to crimp before the bullet is fully seated. This would result in increases seating resistance and crushed cases. Check out the attached for more detailed seating die set up/
Bullet Seating Die Adjustment The trick is to set the bullet seating depth first, then the crimp. This is done as follows; With an empty, sized case in the shell holder, hold the ram at the top of its stroke. Turn the bullet seating die body down over the case until you feel it come […]www.titanreloading.com
Are you trimming all of your brass to the same length? If not some of it may be longer from factory inconsistencies if new, or even once fired, or it could have grown too much. 204 Ruger brass doesn’t typically need to be trimmed too often, but if they’re not the same length and you have the crimp set low it could cause this.New RCBS, all measures correct! I don’t lube the inside of any cartridge, I use anhydrous lanolin on the shell, I believe I may have had it set to deep? Not sure why it only did that to one out of 8. Thanks for advice.