Sharps4590(I think)has a 9.3x75R,which if I recall correctly has a head diameter similar to 9.3x72R. If this is correct, a 9,3x74R cartridge will not fit into an original 9.3x75R chamber.Assuming this to be the case, if 9.3x74R ammo has been used in it;it must have been rechambered.If it has been rechambered,the appropriate answer would be load for it using 9.3x74R cases, but bullets appropriate for the barrel at pressures for 9,3x75R, or less.Rechanbering would have removed some metal from the chamber wall.For a time,9.3x72R and similar brass was hard to find and 9,3x74R ammo was somewhat avaliable.This resulted in some guns, unfortunately, being rechambered from 9.3x72R and similar cartridges to 9.3x74R.If Vic chimes in and his 9.3x75R has a head dia.similar to the 9.3x74R,the above opinion is incorrect.Often,9.3 barrels will be marked with 8.7mm groove dia(also 8.8,etc.),so this doesn't indicate a problem.To complicate matters further,the 75mm just means it would accept a 75mm long case,not that it was the name of the cartridge.To help in determining the proper cartridge, it would be helpful to know if the rifle prints both barrels to the same point of impact with 9.3x74R ammo.
Mike
Last edited by Der Ami; 01/21/15 01:20 PM.