Just had a look at a Remmy long action. The 3.715 magazine falls into the action. The 3.85" Cip Mag can be caught by the front action bottom and possibly rear. To replicate the issue of the magazine going in too far I made a mock-up with my old Atlasworx from my 300wm and a remmy long action using my old 3.715 Accurate magazine. The way it was setup exactly the same happens, magazine pushes into the action and the bolt will catch it. I tried lowering the rear by 3mm washer which was enough to avoid the bolt catching. Even if the magazine was pushed up but I do not know if a new mag release lever would be long enough to get the magazine to feed reliably. One might need to compromise. So far nobody was really bothered about that.
edi
edi