The AKM has a barrel with a chrome-lined bore and four appropriate-hand grooves at a 240 mm (1 in nine.45 in) or 31.5 calibers rifling twist fee. The forward barrel trunnion has a non-threaded socket for the barrel as well as a transverse hole for the pin that secures the barrel in place. The AKM's barrel is installed in the forward trunnion and p