A .318 Flanged WR cer'nly reeks o'propriat'ry cartridge, doesn't it, that man? However, yer could j'st as well use that fine old Martini t'build yerself a .333 Flanged Jeffrey, a cartridge that really did exist. Yer would have t'keep the velocities down, though. The hottest cartridge ever loaded commercially in the the old Martini was the British .303. Yer would need t'look up the SAAMI or CIP specs fer that set o'pressures t'keep yerself out of trouble and in one sound piece, what?