The 55 doesn't have any kind of quick release barrel, it a screws out and in. Although you do have to remove the bolt for that. I bought mine in 1970. I lived near North Haven in those days and knew someone at the Marlin factory and got my introduction to rifles and shotguns at employees discount. Never got over Marlins I guess - good yankee manufacturing. I just went rooting around in some of my old gun stuff and found the card that came with it, it has the blow-up diagram and such. If you want it send me a PM and I'll scan it and send it to you.