So, after an ass load of work that included several different springs in the ARC mags and the PVA spacer kits, I finally threw in the towel on this project. The only way it would come close to working was with a spring from a PR spacer kit. Even then, it was only about 60% function in my CC Axiom. The Rem 700 was slightly better at around 75% function. Both guns are std. 6BR.
With a little more effort, I probably could have gotten them to work in the Rem, but if a mag won't work in both, I don't have much use for it.