The AKM features a barrel having a chrome-lined bore and 4 proper-hand grooves in a 240 mm (one in 9.45 in) or 31.5 calibers rifling twist price. The ahead barrel trunnion features a non-threaded socket to the barrel plus a transverse gap for any pin that secures the barrel in position. The AKM's barrel is put in from the forward trunnion and pinn