Air Arms Owners Club

My air arms alfa proj PCP pistol has begun to leak air from the tank in the butt. It does this when I am filling the tank. I do clock the pistol before I start filling so I suspect that either the rubber seal round the neck of the tank has probably perished or the little ball valve has jammed open. Question, after removing the butt plates how does one remove the pcp tank/cylinder from the pistol to replace the seal. From looking at exploded diagrams of the pistol it doesn't seem to be a screwing. Help!!!

Dont know if you sorted this but first find the leak as recommended by air arms video below.
Nitrile O Rings don't usually "perish" in under 20 years using compressed air though CO2 will perish them. It's more likely the firing valve which is indicated by a leak from the end of the barrel.

Watch "Air Arms D.I.Y: How To Check For Leaks On An Alfa Pistol" on YouTube
https://youtu.be/kLiFF7L26wk

The diagram clearly shows a threaded end to the cylinder which screws directly into the body. (A thread is usually shown as a double line). You will have to simply unscrew the tank by gripping it with both hands or use a rubber type oil filter wrench AFTER SHOOTING OUT ALL THE AIR FIRST.



WARNING: this is all theoretical and deduced from my reading the drawing, not experience.