I do have a lathe but the spindle throat isn't large enough for the compression tube if your thinking of boring.
I do have a lathe but the spindle throat isn't large enough for the compression tube if your thinking of boring. The Gamo seal is quite hard, the ARH small Apex seals are a little more flexible, could try that.. I'm not sure I follow on the button idea over piston seal retainer?Before I do anything I will scope it and throw some lead downrange. If it's as accurate/consistent as my .177 Accu I may swap in a small Apex and see if the compression "feels" smoother. I also have very little lube in it now, that's how I tuned the .177. I won't sweat 40-50 fps if the accuracy is there.Thanks for all the advise and if my dim mind can figure our the " delta button" I'll give that a whirl.
What research I've found suggests I may be @ 50 fps low for CP's, but the gun hasn't had more than a dozen pellets downrange.What concerns me somewhat is how tight the chamber is the last 1/4 to 1/3 of piston travel before reaching the breech. I've turned the piston seal down to slide better overall but it still requires a drift and small dead blow to drive it home. So my quandary is keep it this way and hope the seal doesn't over-wear or consider honing the forward end of the cylinder. That in itself is discouraged by many tuners, in fact, not recommended at all by CDT. I also must protect the real estate owned by the rotating breech and its delicate o'ring. Anyone have an educated suggestion?
On another note, some may recall on the Gamo (b19 powerplant variant) the piston crimps the end piece holding the seal. I've noticed in some guns, and in this case, this gun, the seal retainer spins in the piston. In other words, the crimp is tighter on some guns, than others. Question is, does it make any difference whether the seal is fixed or can spin?