Indeed yes, they used an M1922 M1 .22 for the first one. You can see in the pic how the bolt face of a standard '03 is adapted to small rimmed cases. In this case it's been done to accommodate the R2 Lovell rim, with a tiny steel ring embedded in the bolt face.

[Linked Image from i.imgur.com]

A crummy pic illustrating how the breech of the R2 barrel is configured. Illustrates the half-flat faced/half-coned concept I put forth in my original posting. Again, my question basically is do I have to follow suit as per this example or can I just utilize a simple coned breech. May indeed not be the best forum for an answer (I've posed it several other places), but there's a lot of smart guys who hang out here!

[Linked Image from i.imgur.com]