The main reason hulls crush:
1. too much final crimp pressure.
2. Too much powder,shot or wrong wad.
80% of the time it is too much crimp pressure due to incorrect
3. "Open up" (backoff) your crimp die .
4. Use a "Factory hull" and reset your die to the correct setting.
5. "Mike" this measerment (setting) and log it in your records.
ALL my loads, shotshell, rifle, pistol; have Dia,overall,max,min,trim etc. !!
Reloading is an art........Try to make each load better than the last !!
Good luck Sage