Considerable difference in chamber shapes between these 'Martinis'. From the left Nepalese Francotte, BSA MkII, unfired case. The Nepal has a convex shoulder, the BSA a concave shoulder, and new case has straight shoulder. Fired neck measured 0.510 on Nepal, 0.508 on BSA, and 0.488 new case. The Lee MH die set sizes to about 0.487 which is a lot of brass working.
I think I'll just keep brass gun specific and neck size to about 0.500 for reloads and use soft lead to accommodate the different bore sizes.
577/450 cases from X-Ring services (re-formed CBC 24 Ga brass)
Load 70 grains Goex Fg, 1/2 fluffed cottonball (~5 grains) filler, 2 x 1/8" lubed wool wads, 0.020 cardboard disk, paper (2 wraps 0.004 thick) patched Lee 459-405-HB soft lead bullet, OAL 2.995". This seems to be nice gentle load for these old guns.