I ordered some shells from Vinitagers that are 6700 psi today which I assumed was the lowest he sells. I talked to one guy and he said keep it lite because of the locking mechanism more than the barrels. Homeless I think you are dead right.I will make a photo of the proofs and post them.
I roughly mesured the chamber to the forcing cone but I will measure it with a better stick.
Monty


monty