I took a Crosman 2240 and rebuilt it to I guess you could say a 1740, Lothar Walther .177 barrel, 1701p trigger, steel breech, and a Boss RP valve. My first CO2 cylinder got stuck so bad I had to take the gun apart to get the valve and cylinder out as one unit. The cylinder had stuck on the piercing pin. First I tried to drill the end of the cylinder and hook it out but it was stuck too firmly. I had to hold the valve in a vise, the cylinder with some vice grip pliers and knock it off with a small hammer. After that I polished the piercing pin, reassembled and loaded a new cartrdge, fired about 12-15 shots then put it aside for a couple of days, no leaks so good there, This morning I decided to sacrifice the remainder of the cylinder and degassed and it came out fine. I am hoping that is to be a one time occurance. Anyone else have such an experience.