Thread: Rem 700 magazine well

I have acquired a Rem 700 in .222Rem. Yeh, I know - 222 hard to get unless you reload. I do a bit of that.
My puzzle is that within the magazine well is a small oblong box section part which appears to be a filler of some sort which reduces the length of the well, for the little 222 cartridge. Problem is, it does not seem to have any mechanism to secure it in a fixed position within the well. It seems that the follower plate rides on the front edge of that box section, but I may be wrong. If I open the floor-plate, it simply drops out.
I've looked at a number of parts diagram images/lists and nothing is shown for that part.
Can anybody point me in the right direction for info' on the Rem 700 action when the little 222 cartridge is used?

Thanks,
49er