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 Post subject: El Gamo Mod EXPO
PostPosted: Sun Sep 04, 2016 4:09 pm 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2782
Location: Somewheres near the Atlantic
Family friend dropped this air rifle for me to fix.

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As you can see its in rough shape. He said it didn't work all the time.

So I ran it across the chrony and only avg 340 FPS with 7.9s. Cocking effort is very easy. Not sure the FPS that it should be.

Passed the tissue test so the breech seal is good. I added some drops of oil in the chamber to see if it increases FPS and it did not.

So I took it apart. No broken spring. The piston needs to be polished and the tube needs to be polished. But here is the issue.

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A piece of copper wire somehow got in.

Now the fun part is finding seal kit for this that NOT going to cost as much as he paid for it. I have a funny feeling between the amount of work to clean it up, polish the parts, find the seals it be worth it to buy something new if it doesn't have sentiment value.

How you spend your Sunday?


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 Post subject: Re: El Gamo Mod EXPO
PostPosted: Sun Sep 04, 2016 7:34 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1271
Location: United States
What teh F? I guess if something can be screwed up then a human will find a way. I can't really tell the seals condition from the pix but I rekon some oil might make it nice again? Minus the copper of course. Or by getting a conversion seal kit to use a modern seal. The tube can be sanded w/o too much effort or cost, and I posted my method here somewhere last week. If the exterior of my gun looked that bad I'd only consider one option; sand blast and cold blue. It turns out very nice, but is a matte black rather than shiny, obviously. Looks great imo, especially when flawed to the point that shiny will never be an option. I use 60/80 Garnet which imo turns out way better than common media which is closer to 36grit. Or just use phosphoric acid in whatever form is available, then blue. Or paint it. I like paint but don't have good luck on things like guns with sharp corners and moving parts.
I'd also be very concerned about the bore. If the exterior is that rusted then the rifling may be trashed. Some acid and possibly light sanding, that is if there's enough bore left... So I guess then I'd verify that before working on anything else. If it has no personal value then I'd be reluctant to do anything at all, but even then I still do things for the challenge and learning experience. Maybe tell your friend you'll trade the work for a nice scope ;)


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 Post subject: Re: El Gamo Mod EXPO
PostPosted: Sun Sep 04, 2016 8:21 pm 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2782
Location: Somewheres near the Atlantic
Chevota wrote:
What teh F? I guess if something can be screwed up then a human will find a way. I can't really tell the seals condition from the pix but I rekon some oil might make it nice again? Minus the copper of course. Or by getting a conversion seal kit to use a modern seal. The tube can be sanded w/o too much effort or cost, and I posted my method here somewhere last week. If the exterior of my gun looked that bad I'd only consider one option; sand blast and cold blue. It turns out very nice, but is a matte black rather than shiny, obviously. Looks great imo, especially when flawed to the point that shiny will never be an option. I use 60/80 Garnet which imo turns out way better than common media which is closer to 36grit. Or just use phosphoric acid in whatever form is available, then blue. Or paint it. I like paint but don't have good luck on things like guns with sharp corners and moving parts.
I'd also be very concerned about the bore. If the exterior is that rusted then the rifling may be trashed. Some acid and possibly light sanding, that is if there's enough bore left... So I guess then I'd verify that before working on anything else. If it has no personal value then I'd be reluctant to do anything at all, but even then I still do things for the challenge and learning experience. Maybe tell your friend you'll trade the work for a nice scope ;)


Once I removed the copper the seal was toast. It hasn't been oiled in years and totally dry. Pricing out the conversion and looking at the cost of what he paid for just the seal. Not including the other work to keep it from damaging another seal. That was the Vortek or whatever 25mm seal and kit. Being that the plates are all cracked up.

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If anything it just get the steel wool and maybe blued, or just rust paint.

Actually the bore is mint lol.

Probably be able to find something else for just as cheap. I mean the cocking effort was around a Crosman raven. So it cannot be any more than a 400 FPS airgun.


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 Post subject: Re: El Gamo Mod EXPO
PostPosted: Sun Sep 04, 2016 8:46 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1271
Location: United States
I see, $16.80US from Vortek. Seems reasonable to me... If not willing to spend that you could always make a new leather one or make an existing Crosman seal fit. I'd do anything I could to lose the leather seal, and for the $ I think the Vortek kit is worth it vs trying to do it yourself.
I can't really say about that model but it wouldn't surprise me if it broke 600 with 7gr. If you give me the bore and stroke I can estimate, but it'll just be an est. Then of course you have spring options as well, but if it were mine I'd want to see how it does with the orig spring.
Regarding sanding the ID of the receiver to repair whatever damage, I posted a few pix here on 25 Jan:
topic72765-15.html


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 Post subject: Re: El Gamo Mod EXPO
PostPosted: Sun Sep 04, 2016 9:13 pm 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2782
Location: Somewheres near the Atlantic
IF he doesn't want to fix it. I'd offer him like 20$ throw it in the comer for rainy day.

I already got a airgun that shoots 750-780 with 7.4's.

Thanks for the link. But I'm familiar with deburing receivers.


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 Post subject: Re: El Gamo Mod EXPO
PostPosted: Mon Sep 05, 2016 9:51 am 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2782
Location: Somewheres near the Atlantic
Polished up the piston, deburred and cleaned the inside of the receiver. Now I wait to find out what the guy wants to do.


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 Post subject: Re: El Gamo Mod EXPO
PostPosted: Wed Sep 07, 2016 1:05 am 
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Joined: Mon Sep 03, 2007 7:56 pm
Posts: 173
Location: Sidney, BC.
You might want to try a Crosman phantom piston in there,,,you might not realize that all the Chinese / Crosmans are copy's of the Gamo air rifles.
KEN.


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 Post subject: Re: El Gamo Mod EXPO
PostPosted: Wed Sep 07, 2016 8:24 am 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2782
Location: Somewheres near the Atlantic
KEN. wrote:
You might want to try a Crosman phantom piston in there,,,you might not realize that all the Chinese / Crosmans are copy's of the Gamo air rifles.
KEN.


Thanks Ken, But I know the crosman phantom piston is much larger in length than this Gamo piston. Kinda trying to fix this on the cheap.


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