I have had this CFX the longest of all my current arsenal. Lots of pellets through it. It started to lose velocity and on the chrony It dropped with each successive shot. Had to be a seal so I ordered seals from Custom Airseals in Australia. Those blokes are good. Bit of delay in delivery due to staff problems in the Melbourne post office but they warned me about that.The seals arrived and were installed. Their custom made piston steel is far superior to the Gamo seal.The rotary tap/breach seal was worn away and replaced with their kit seal.The rotary tap as you know has a 1mm seal that the tap rotates in. Tricky getting that into the compression tube past all the cut outs and sure enough I cut the o-ring. Bugger.. But there in the packet was a spare. They knew I was going to muck up the first attempt. That is exemplary service.
I had the Custom Airseal gas ram in it and I thought it lost pressure so I took it out and put a spring back in it. Turned out the seals were the problem. I am going to put the gas ram back iin and see how it shoots. I have ordered a new spring because I think the one I have in it was from my 12 ft lb period but I want more than that now. Not sure how it will end up . I guess spring powered because I think that delivers more power. I have definitely replaced the collar around the spring guide because every time you assemble the gun the trigger frame carves a new seat. Spring should arrive in a day or so. The spring guide I have in the gun does not prevent spring distortion. I am not sure if it is a factory one or one I made myself. I am off to put the gas ram back in to see how much power it delivers.I have a preconceived idea that gas springs leak over time. How can they not? I can't say definitely because when I put the gas ram in new I did not have a chrony.I had been using an HW95 piston seal in the gun and it worked very well. When I took it out there was no damage at all.The big fault was the breach seal that appeared to have crystalised over time. I guess the many heat cycles from lots of shooting had sort of cooked it.
I tested the Gamo with the same spring and new seals and it put out 11.7 ft/lbs.I then turned up a top hat that added 14 mms to the preload and it put out 11.91 ft/lbs.I was expecting a bit more than that. I would like to get it up to 14 - 15 ft/lbs. I suppose I will need a new spring.