For years I had thought the 375 Magnum Flanged was simply a rimmed version of the 375 Magnum Belted. While looking up rim thicknesses I found this is not so. The 375 Flanged differs in many measurements from the 375 Belted.

Most significant, the case length, length to shoulder, and OAL are all greater than the 375 Belted. Enough so that if you shaved the rim off it could not be expected to chamber in the 375 Belted chamber.

This as opposed to the 400-360 Rigby Rimless which will chamber and fire very nicely in a 400-360 Rigby Flanged chamber.