I recently examined a 7x57 Mauser cartridge, brass case, nhs, RN CN SP bullet with a .25" diameter primer. Does anyone know of a manufacturer that used this size primer in this calibre?
I believe that BIRMINGHAM METAL & MUNITIONS Co produced this cartridge with no hs and the c6.4mm large primer.
.25 was an old standard british berdan primer used in many older cartridges including the .303. I haven’t seen a 7x57 with one, but BMMCo is a very good call.