Sounds like a pressure issue. .303 sav headspaces on the rim as all rimmed cartridges do. Is your bolt not in battery?
If your headspace was excessive you would be getting blow by if your OAL was long your brass would show Markings from the chamber. Your saying your backing out primers?
Solid frame or takedown?
What a fuuckin dipshyt. Backed out primers are what happens with low pressure cartridges fired in rifles with excess headspace. Very commonly seen in old lever action .30-30's. The firing pin knocks a cartridge as far into the chamber as it will go, powder ignites and plasters case walls tight to chamber walls, there isn't enough pressure to stretch the case head back to the bolt face so the primer backs out. If you don't know this you should STFU and quit trying to be Mr. expert on the spot. Moron.
