Sandgroper,

The 360 2-1/4" can be formed from 9.3x72R brass. As far as bullet diameters there were two. .358" and .366". I used to own a I. Hollis and the bore diameter was .366". If you get one you will need to slug the barrels to determine the diameter. Dies can be gotten from RCBS. Shoot up to and including 300gr bullets. You will like this caliber. Very mild recoil.

Corbin