1st Tune - Gamo Bull

[WxRadarman]

Purchased my first break barrel, a refurbished Gamo Bone Collector Bull Whisper IGT a few back in Jan.  The Bull is a scope killer -- I've been thru 5.  Someone suggested that the seal might be hard, causing the scopes to rattle apart.  Had some accuracy problems the past few days, so decided to take it apart today. 

The seal is in bad shape, so I hope after deburring, polishing, cleaning it up and replacing the seal, it will shoot more accurately and not kill scopes every 200 pellets.

Built a very simple spring compressor today to help with the project.

[WxRadarman]

Never looked at a seal before, but I think this one is in pretty bad shape.

[WxRadarman]

1st time deburring and polishing one of these.  Dremmel came in handy and the threads on using dowel really helped.

I'll have to save some money and get me the upgraded trigger.

[Tater]

Wow Keith, great job on it! I've never seen a seal up close either, but from other members pictures I've seen, that did look pretty bad.
I hope it's a good shooter now and I bet it will be easier on scopes now.
Thanks for posting the pics and write-up, it will help someone like me in the future that finally attempts their first tune.

[WxRadarman]

Thanks Tater.  Still got to order the new seal, so it's not back together yet.

[TooJung2Die]

Declining accuracy, declining velocity, noise and harsh recoil are symptoms of a defective piston seal. That one is badly damaged. I think your scopes will last longer after you replace the seal. The piston was probably slamming home because the seal wasn't holding pressure. The reverse recoil of the piston stopping is harsher than the initial recoil of the piston beginning its forward motion. That is what kills scopes.

Jon

[WxRadarman]

Finally got the seals, the lube and the time to complete the tune.

Rifle went together well and seems to be shooting OK.

I put about 100 pellets thru it today and I'm working to zero the new Crosman 3-9x32 Scope I put on it.

Also stuffed the stock with foam insulation.

Hope it shoots more consistently and quits killing scopes.

[longhunter]

yeah, that seal was toast. you'll probably see an increase in velocity, as well. break the gun in with some heavier pellets. that way, you won't kill your new scope. it'll also help the gun break in a little faster, and any dieseling will go away, sooner. and, don't use any super light, alloy pellets. you'll kill your new seal, as well as the scope. that gun isn't intended to shoot light pellets.