I need to know the rim thickness of:

375 H&H Flanged Magnum;
375 H&H Belted Magnum (just the rim behind the extractor groove, and;
375 2 1/2" NE (and also its rim diameter - COTW says .523 which seems small).

Having maligned Bertram Brass, possibly unfairly, it has occured to me that my case life problem may be head space related.

Rifle Cogswell and Harrison box lock non ejector converted from 375 2 1/2 to 375 H&H Flanged. Bertram cases last 2-3 firings whereas I get 8+ reloads from 375 H&H Belted cases when I lathe turn the rim off. I load 75gn AR2213 (H4831) under a 250gn projectile for 2450fps so it should be running under the 375 2/12" 17 tpi.

Thanks for any help.

mike