The original CR1470 barrel is 27.5" long with the breech end similar to that of the .303" original. It has a diameter of 0.93/0.92" at 4" from the breech end, tapering to 0.79/0.77" at 1.31/1.30" from the muzzle and left with the 'snakeskin' hammered finish. This last portion is turned down to 0.670/0.667" dia to suit the foresight block (original .303" Mk 1 type bored out to a larger internal diameter to suit). Later barrels were manufactured on a different hammering machine which could only produce a parallel blank so they had to be turned along the complete length, leaving a stepped portion in the middle where a lathe steady was used.