Gamo Hunter 220 takedown and tune
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Gamo Hunter 220 takedown and tune
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Topic: Gamo Hunter 220 takedown and tune (Read 1612 times))
bsagunner
Shooter
Posts: 43
yes
Real Name: Tony
Gamo Hunter 220 takedown and tune
«
on:
September 26, 2017, 11:46:48 PM »
Hello,
I am taking down my 220 to tune. I have an E3650 and small Apex seal from Maccari on hand to install. But all is not going as planned! The barrel breech bolt will not loosen despite a dowsing with Croil over night. I tried a propane touch today without success either. I bought the rifle used and and it appears that the previous owner did a lube tune and must have used lock tote on this bolt!! The heat has ruined the plastic barrel block washers too. To get at the internals I had to knock out the pin on the cocking arm, at least that went well. The good thing is I have some spare barrel block washers and a breech sleeve but not a spare bolt. That's on order from JG Airguns. I am off to a machine shop some time this week to have that bolt drilled out.
Can anyone tell me what ill effects would substituting steel washers in place of the plastic ones have in the gun?
Thanks
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St Georges, Grenada
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Honorary GTA Moderator
GTA Senior Contributor
Posts: 9703
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Real Name: Thomas
Re: Gamo Hunter 220 takedown and tune
«
Reply #1 on:
September 27, 2017, 12:59:58 AM »
You jumped into your tune with inadequate information and it has created far more work than necessary. It is not necessary to remove the barrel of an airgun to replace the spring and seal. Gamo uses some kind of epoxy at the factory to keep the pivot bolt from being removed. That was not likely the former owner at all.
You may find the Apex Small seal too large. It should take two to three pounds of pressure to move piston and seal through the compression tube - not much more and not less.
The washers are a common thing to replace in Crosman as well as Gamo guns. I have attached instructions in response to posts several times. Unfortunately they're on another computer at the moment. I start with a 3/8" bronze thrust bearing. They're about 3/4" outside diameter and 1/16" thick. I place them on a bolt, tighten a nut, and spin in a drill while applying a file to the edge under pressure. The goal is about 0.68" outside diameter. I bevel the edge to about 45 degrees when done.
If you leave them full thickness your gun may shoot off to one side. Take them down to about 0.060" and try them. You can do some extensive measuring to find the perfect thickness. Mine worked out to about 0.054" thick. That was almost too thin. It's easier to thin them further than it is to add material back.
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Near the Southern Coast of Washington State
Real knowledge is knowing the extent of one's ignorance.
bsagunner
Shooter
Posts: 43
yes
Real Name: Tony
Re: Gamo Hunter 220 takedown and tune
«
Reply #2 on:
September 27, 2017, 10:54:15 PM »
Well it seems like I am learning the hard way!
I followed CharlieDaTuna post on disassembly to the letter.
charliedatuna dot com/airgun_docs/B19%20Super%20Tune.doc
Anyway my intention was to replace the barrel block washers because I detected a little barrel side ways movement - that's why I bought spare washers. Several post online advised on the Apex small seals too. I will ask my machinist to turn a couple bronze washers for me.
I just hope the bolt removal goes well. It would be a pity to junk this rifle. It shot very well, just buzzed uncomfortably bad, so bad that it was downright unpleasant to shoot. Not to mention that I have already spent a fortune on it. Another Airgun Blog writes that after dissemble, he just lost interest in the gun. I ain't giving up so soon though.
I think it's very mean of Gamo to put plastic washers on the barrel block and then epoxy the pivot bolt!! I wonder what surprises await me when I teard down my Swarm. The accuracy renders it pretty useless as a rifle. If I fail in turning it into a shooter I may as well use it as a cricket bat.
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St Georges, Grenada
bsagunner
Shooter
Posts: 43
yes
Real Name: Tony
Re: Gamo Hunter 220 takedown and tune
«
Reply #3 on:
October 01, 2017, 11:13:41 PM »
Well I am finally got the pivot bolt off. My machinist used an impact driver to do the job. I deburred the slots in the chamber, tarred the E3650 spring, mollyed the piston and other metal to metal areas and dabbed a smear of silicone grease on the Tesla seal which I had to sand down a bit until it fit like I think it should fit. I fitted 2 new OEM barrel block washers and reassembled everything. It was dark by the time I was finished so I could not cronny it, but I did shoot a few rounds into the ground. The rifle now shoots with a solid thunk. No more buzzing! I do not care if there is a loss in velocity, as long as it is pleasant to shoot I am happy. Tomorrow it's velocity and accuracy.
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St Georges, Grenada
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Gamo Hunter 220 takedown and tune