cal: 5.56, full-auto, mag not included, barrel: 20", barrel stamped "CMP Chrome Bore", left side stamped "Russell P.D.", SN: 9310573; NOTE: THIS IS AN NFA/CLASS 3 REGISTERED TRANSFERABLE MACHINE GUN. ****If you do not know what that means or requires for purchase, please do no bid on this item until you have familiarized yourself with the NFA/Class 3 process and are willing to commit to it. If you are unsure of the procedures for purchasing an NFA registered weapon, please contact us, BATFE, or your local reputable NFA/Class 3 Dealer. $100 transfer fee per firearm!