Tip for crush washers with muzzle devices that need to be timed.
Tighten slowly and back off, repeat until you have almost timed it correctly. Then make final turn to time.
By backing off it allows the crush washer to compress enough that you can actually time the muzzle device. You should never "sand" them to make the muzzle device time properly.
Kalashnikov Klub member # 7.62x39