Primer pocket.
Hello,
I wish that I could provide the answer to your problem.
It's very strange, I have loaded many, many thousands of rounds using CCI primers, 100% for 0.223", a RCBS primer pocket tool and a very old Lee primer "loader", and I have never had a problem like yours.
Perhaps try a new pocket cleaner and another batch of CCI primers.
When you are loading the primer do you find it unduly difficult to insert the primer, pressure wise?
Good luck with solving the problem.
6.5 55 SWEDE.223 HOWA VARMINT NIKON 8X32X50 -.22LR CZ STYLE-16" .17 HMR CZ AMERICAN-16" SIMMONS AETEC-12G BERETTA A.302,AYA NO 4,BAIKAL O&U