Mikey; The gun was probably rechambered like the French MAS 49/56 they remachined the barrel back so the 308win/nato(7,62x51) round would fit because the 7.5 french(7,5x54) round is longer, its the same bore size, well there using the .308" diameter bullets in both the 7,5 swiss and the 7,5 french for reloading. There only setting the barrel back a few milimeters to shorten up the longer chamber. BigBill