I never bother with this balloon business, check mine in water, bubbles will appear immediately. Dry with cloth and hair dryer, no problems. Think it comes from when I used to wash my SLR in the shower after exercises in the mud, always had the best kept weapon in the squad.
Baz
BE AN INDEPENDENT THINKER, DON'T FOLLOW THE CROWD
I just have to laugh when I hear guys talk about sticking balloons on things, especially over the end of the barrels. I put whole CO2 pistols in buckets of water to check for leaks, its all a matter of years of experience and hundreds of repairs with no problems, sort of builds up your faith. Never had a complaint except from gingernut and his rebellious shiny pistol which nobody can fix.
Baz
BE AN INDEPENDENT THINKER, DON'T FOLLOW THE CROWD
Remove cylinder and see if it loses air. If it doesn't, check the barrel screw above where the cylinder screws in and under the barrel. Mine leaked when that loosened. I cleaned the grease off of the screw and used a tiny bit of the weakest threadlock to secure. Never leaked again
Danny
My collection = Ratworks BSA Scorpion T-10 .177, HW100KS .177 (tweaked by me), PP750, Crosman 1322 and 1377
Let's start again! Is it the cylinder that leaks or the rifle? Unscrew the cylinder n leave a few days to see if pressure drops! That will tell u I suspect that it's the rifle there's loads on YouTube to follow from memory there 3 o rings on the inlet side! The smaller one dose the business end but there's some other ones aswell when u remove the 8mm brass insert!