I shoot a Model 10 .223 and use Lake City and Lapua brass. My load is CCI-450 primers, 24 1/2 gr of CFE223 pushing a 75gr A-Max. I use Redding Type-S match dies with a .244 collar and bump the shoulder back no more that 4 thousandths measured with a Hornady headspace gauge.

My LC brass started experiencing case head separations on a regular basis and I quickly discovered the bright ring above the base of the case as the tell tale sign. (by the way, I now carry a short piece of cleaning rod and a brass bore brush to remove the half of the case left in the chamber)

Thinking that the problem was the LC brass I bought some Lapua match brass and after only three firings I noted the dreaded bright ring at the base of a few cases. Drat.....

Research online has not been much help. Advice on how to prevent case head separation is basically watch for the line, feel the inside of the case with a paper clip and throw the case away.

Some guys on here claim to get 20 or 30 firings from cases without any failures. I suspect that I'm doing something wrong with my FL sizing die but can't seem to nail it down. Any constructive advice will be appreciated.