Often lightly loaded ammo makes a gun seem like it has headspace problems when it doesn't. The case just doesn't come back and seat the primer again.
One shot had a complete head separation. I just use that rifle for cast bullets long enough to run into the rifling. It seems to be happy being used that way.
Paul B.
I'd think that with headspace issues that bad, you'd have misfires every now and then. That, or your firing pin protrudes too far as well. I'd get a cast of the chamber or get it to a gunsmith, were I you. Case head separation on first firing of brass signals bad brass more than a bad chamber.
