30-30 brass, I begged Starline to make it!

[RPRNY]

I would suggest taking that rifle to a competent gunsmith and having the headspace checked and see if someone has buggered up the chamber.

Sound advice from Don. That's step 1. Also, if your (OP) issue is predominantly case neck splitting, annealing your brass and using a Lee Collet die rather full length resizing may help.