is it the seals

That sounds perfect. I'm guessing your happy with the results. I've been looking into chrome polish for its abrasive qualities and it has two very soft/fine polishing compounds. I'm going to try a bit on the end of piston, clean it with solvent and see if it's smoother. If so I might do the barrel the same way. Lap it in.
Probly do it after back together and tested.

So gun back together.
Everything polished, including trigger. Everything running smooth. (better than ever has)
Trigger still way to much play before engages sear so might file that back a bit more or get a longer adjustment screw.
New volicitys (about 30 shots in)
Everthing in 700fps. Last 2 didgets every of shot.
12,05,10,16,19,15,12,13,12,15,09,17,15,14,05,07,05,00,17,17,15,16
HI:734   LOW:700 AVG:713
Re zeroed scope.
Not happy with grouping. Trigger pull may be affecting my shooting.
Pellet may be to lite for 700+fps
Play more tomorrow.
Pellets ftt 14.66gr. Had quick shot with aa16gr not much better.

Any ideas why spreading? Including shooting techniques. ( I pull much tighter groups with tx at 50m)
Comments appreciated.

Edited by kruzaroad - 22 Aug 2022 at 5:52pm

I shot it to 15 meters with open sights and thought sweet and put scope on.(prob should have gone further)
It currently has a gun City air rifle rated scope,in a one piece base, on gamo recoil damping base they come with.(red dot won't even look into till firing strait)
I have no idea about the crown but will check it out on Web. That comment does make me wonder if its clipping the built in suppressor baffle. Will check that, probly remove internal baffle and see if tightens. I've seen no damage in bore but that's just looking through barrel with eye, so no noticeable damage might be better description.
As for the groups if that's as good as it shoots at 25 meters, it's no good to me. I've already taken a hare with tx that had a pellet in rear leg from gamo prior to tx ( that would have been aimed as a heart shot on stationary hare) I've seen your videos and would find it hard to believe that you wouldn't be putting pellets through same hole at 25m
Cheers you've given me couple more things to look at.
It also came standard with a washer as spacer behind gas ram, wonder if removing that would help without dropping the power to much. hmmm

Ha ha, sorry, I really meant to say that I would find it hard to shoot good groups at 25 m with a red dot sight. slightly older eyes can struggle to focus on the close red dot and target at the same time. 

Ive sent the pics to gamo distributor and asked if this could be the issue with accuracy and will gamo replace the barrel. They also put a 5mm washer behind the gas ram (as standard) which I'm probly going to take out.It reeks of a gun that has just had a spacer put in to upgrade the power and I suspect that the piston is hitting the end of cylinder harder than it should, increasing recoil and doing the seal no good. I'd rather a lower power rifle (providing its not to big a drop) that hits where its aimed more than a faster rifle that puts pellets into the rear of animals your aiming to the front of.
This gun has been a major pain in the arse, but worth its weight in gold as a learning curve that's for sure.