is it the seals

So the gamo does some wonderful groups then impact Point goes astray. I've got new seals on the way but have just chronographed it. Seems a bit of variation to me.
What is the view of you more experienced technical ppl on this?
All pellets were weighed and sized.
high 694 low 650 Ave 668
shots all in 600fps last two didgets of numbers in order.
79,90,94,84,94,70,66,71,68,87,73,54,64,
58,50,68,59,68,55,60,64,65,56,57,62
Any thoughts appreciated.

Cheers. The rifle has been very problematic. I voided the warranty ages ago when I removed the mag due to pellet deformation . So that is out. I check the pellets are seated in far enough every shot. When I removed the piston it wasn't that great looking, so I think the crossman oil every 250 shots is something I'll start doing after the seal replacement. Due to fact it will group for x amount of shots, I don't think it's the scope,as it will start regrouping again without adjusting the scope (deviation is way to much from aim point to be just my shooting and wind. I've looked at that. Blame shooter first and work back from that) and Ive lock tighted the screws they haven't moved. The info the red dot is awesome, Ive been toying with the idea, as I'm going to turn it into the scrub gun/short range (if I can stabalise it) and keep the tx as a longer range rabbit Gun. Im stoked to know that the red dot is used by another shooter and will now look further into that option. Eventual I'll replace it and muck around with my shock gel and carriage idea.
So cheers appreciate the response.
Any one else with ideas or options I'd still love to hear them.

I'm pretty sure it's not deforming as I check it's sitting below the edge of the barrel, but I have a little pusher thing that I can seat it in further with so I'll try that tomorrow too double check. The seal is on the receiver side (model is roadster)
guns going to get stripped,internals cleaned, polished,resealed,relubed put back together making sure it's all tight and working well. Sighted in at 10 then 26 meters on open sights, if still playing up after that cut losses won't waste any more time on it.
Lots of ppl who's gamo work great for them, I may have just got a bad gun/model but hopefully just wants some tlc.

Edited by kruzaroad - 13 Aug 2022 at 5:55pm

So pulled the gamo open and had a good look. Not impressed. Done a bit of sanding to inside of stock as had rub points but at irregular intervals. It has ribs under it to hold bottom of receiver. All along one side and just front and rear on other side. Can't see that helping an even shock vibration pattern. But I may be wrong.

Had a worn rubber on one side, where pin that holds trigger housing/piston housing to receiver.

Piston seal was embedded with a chunk of lead right at seal edge.(bottom of pic)

Seal Edge crap too

Sprayed with brake clean to see what came out, metal filings and brown crap I assume is protectent for metal when shipping.

Have just got ahold of vaughans for new rubbers.Piston and barrel seal arivved yesterday. But will rember that for next time thanks.
I'm currently looking at piston which has so much space between it and the gas plunger it's been rubbing on the gas housing during cocking.

Need to make spacer. (sujestions appreciated)

The gas ram end has play where it sits in the rear housing.
Noticed that one of spring clips on trigger (previous pic) is broken.
I have nothing against gamo but I'm starting to think I scored a rifle made from parts taken off other rifles that didn't make the grade.
Sigh.

Edited by kruzaroad - 17 Aug 2022 at 10:13am

Just cut out an insert from milk bottle that stops the movement of the piston head so will get thin sheet metal for that tomorrow. The gas tube is thinner, but has that grove around it which would be ideal for a grommet so that's a good idea. Cheers. Aaah a lathe if only, milling machine for stock be handy too. sigh. Solid Bush mechanics for me.

I've just epoxyed the plastic from milk bottle to the piston ram head as it's such a good fit and doesn't move as it's always hard against the piston. The gap between the gas chamber and the piston is rediculous. Is about 3mm all the way round. I'm going to expoxy a shim on the gas chamber, piston arm end, to keep the piston level enough to go over the oring/grommet I'll put on, without it just chewing it up. It's Friggin crazy there's no way that gamo makes guns so far out of spec.Something is not right in my opinion.

Edited by kruzaroad - 17 Aug 2022 at 12:54pm

gun is stored horizontal,usually vertical when closing the barrel,I think the bit of lead was from the mag when it was on, it damaged the pellets and didn't push them in very far. The scraping on the gas chamber was at the bottom the piston damage top (except bit of lead). That piston pic is after the brake clean and wiping it! Gun City who sold it know nothing , they recommended young's when asked if they could get seal in. Hunting and fishing tried to order seal but couldn't get one as gun City is sole supplier of that model. I voided the warrenty taking the mag Off.
I'm dealing with vaughans now who are the gamo importer (have been since mag issue, which I decided to not take free replacement) . They sujested might be easier to get whole trigger/gas housing instead of back rubber, and got a quick rundown on what I have to do with it to get it running and I don't need the expense.So they know about it. Their OK he's looking to see if he has it tomorrow.
But saving grace is I have tx, which has been a pleasure. Everything with that process was smooth from enquire to delivery to shooting. When I asked about a tuning kit he recommend not to put one in as they are constantly removing them and turning back to stock.
Live and learn. If I had the machinary to make the parts I'd be in heaven and loving all the faults. For now number 8 wire.