Don’t know if this helps out but last night after finding out that PMAG for long action Christensen Arms rifles only work with metal mags the red neck engineer in me had to find a way. I found some foam I use for cheek risers and other recoil pad fillers and cut a section of 1/4 foam out along the edge and it works great to lock in my 300 win mag pmags into the mag well. No slip slide of bumping around and smoother feeding into the rifle then metal mags. Hope this helps people in their ventures wanting to run pmags on Christensens long action.