Poochg, bullet setback is also a SERIOUS consern with the .357 Sig and the .400 Corbon, and, even some factory ammo has been having problems with this issue. Checking ALL your ammo of these calibers to make sure the bullets are tight and proper is IMHO imperative.
But... this is not what i am refering to with the issue of the headspacing on the rim. What i am talking about is the shoulder "giving out" and "pushing in" shortening the OAL of the case... preventing the rim from headspacing properly.
I agree, headspacing on the shoulder is much better. I dont know why these cartridges werent designed to headspace on the shoulder.
The only thing that should come between you, and any gun... is comfort... Get Agrip!
Your first and best weapon and/or tool is your mind.
Warning, anything I write is intended to manipulate you into using your mind.