I may be wrong about this, but the "303 Mauser" was the British designation for the 7.65x53 Mauser/Argentine/Belgium cartridge. It became the "303 Fraser" when the ratchet bullet was used. They all fit the same chamber. Fraser also developed the propriatory "303 Fraser rimless" to be used in the M93-95 actions having different chamber dimensions because they could not feed the 303 rimmed British round. I believe they later purchased the slanted magazine M98 actions from Rigby in 1900 to handle the rimmed cartridges. Fraser's serial numbers seem to indicate that rimmed caliber Fraser's were built after 1900. Any thoughts?