Gamo MC the Super Gamo

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Gamo MC the Super Gamo

Postby Tank » Tue Mar 25, 2014 8:40 pm

Super Headache more like it!

Did you miss me guys? Prolly didn't notice I vanished. Well anyway, now that the demands of my day-job are slowing a little I have made a start on a Gamo-MC the Gamo Super. Actually this is a very nicely engineered Target Rifle. Plenty of bits, all well engineered, and fit well together.

First off, these guns are not new. There are no spares, anywhere. Nobody works on them now and many people believe them to be either "unrepairable" or, worse, "Junk".

Outrageous. These are very fine target rifles. The system is very innovative, very unique. There is a piston within the piston. Very clever and more about that later. Let's get back to basics and here we go. Didn't take much taking apart this one, it came to me in a bin bag! :D

First up, the piston, need to get it apart and a little judicious use of a bit of heat in the vice, that is not a bit of leftover brass pipe, you can't see it but it is a blowtorch:
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When it was apart I could get a look see as to how we were doing inside the piston itself:
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Next up, the cylinder itself, a complicated piece of engineering. I can't help but think someone had bought a multi-function CNC machine and decided to make something with it and this is the result:
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It is a double acting cylinder and locks up securely. The little pip you see just to the left of the keyhole is actually the Firing Pin or in this case the firing actuator. And yes, for the sharp eyed amongst you, there are two cylinders here on the bench. The boys just know I love a treat and I don't have one of these to repair, I have TWO :shock: In the same week.
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Finally, despite having the outward appearance of being well maintained and cared for it is obvious to me that these guns have been "stored" in collections. This is what I found on the back of one of the cylinders, it is solid, hard and embedded gunk. Nothing the rotary wire brush won't get off:
Image
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Re: Gamo MC the Super Gamo

Postby Tank » Fri Mar 28, 2014 8:07 pm

So, bit more progress today. I machined the crowns off both of the pistons and created a cap from Aluminium Bronze (because that's what I had to hand) and machined them down to the correct spec. for my planned conversion to 'O' ring seal. They measure out to within a thou of each other so I am quite pleased. I used the only machine that I have that doesn't have Digital Readouts. Bit of a result:

Image

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Re: Gamo MC the Super Gamo

Postby dnic » Fri Mar 28, 2014 11:57 pm

Hello Tank,

Hmm, the smell of oil and grease, whirring of lathe, heat of the blow torch :D

I am going to enjoy this post, keep it coming :clap:

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Re: Gamo MC the Super Gamo

Postby Tank » Sun Apr 06, 2014 7:34 pm

In the third and fourth pictures down, posted above(?), you can see the firing valve just protruding from the pressure cylinder. This valve has two seals on it, you can see the remnants of one in this photograph:

Image

There are no seals available of course so it was time to make some. I have found, when making seals this small from 60 durometer urathene, that it is much easier to turn the seal from a much bigger piece of material:

Image

The seal is truly tiny, a 1.35mm hole is required to mount it on the valve:

Image

And here it is, on the valve, only one more to go and then I can start on the secondary seals:

Image
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Re: Gamo MC the Super Gamo

Postby micken » Sun Apr 06, 2014 7:46 pm

Good work Graham, I'm loving the precision machining. Great thread, atvb.

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Re: Gamo MC the Super Gamo

Postby Adam77K » Mon Apr 07, 2014 5:38 pm

Nice, you don't see many of these about! I remember them from the mag reviews back in the 80s. IIRC they were somewhat mixed.
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Re: Gamo MC the Super Gamo

Postby jedu » Fri Jan 02, 2015 10:07 pm

Tank wrote:In the third and fourth pictures down, posted above(?), you can see the firing valve just protruding from the pressure cylinder. This valve has two seals on it, you can see the remnants of one in this photograph:

IMAGE

There are no seals available of course so it was time to make some. I have found, when making seals this small from 60 durometer urathene, that it is much easier to turn the seal from a much bigger piece of material:

IMAGE

The seal is truly tiny, a 1.35mm hole is required to mount it on the valve:

IMAGE

And here it is, on the valve, only one more to go and then I can start on the secondary seals:

IMAGE



Hi

I have just joined the forum in my quest for a durable replacement for the MC valve. I am just missing the pictures in this post... and another comment. Have you ever tried this solution from airecomprimido.net?

Image

It consists on using o-rings (size in mm) the small one 1.7x1.8 for replacing the green one and the two big 3.5x1.5 for the replacing the red one, material should be PUR90, NBR90 or NBR70. This user reports sucess.

Have you another ideas?

Best regards and thank you

JEdu
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Re: Gamo MC the Super Gamo

Postby Tank » Fri Jan 02, 2015 10:28 pm

Well I am pleased you did join as I have realised there was an error in my DNS records so thanks for that.

It is a good solution the two "O" rings but I can make custom seals so I just duplicate the originals, because I can.
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Re: Gamo MC the Super Gamo

Postby jedu » Sun Jan 04, 2015 9:13 am

It is a good solution the two "O" rings but I can make custom seals so I just duplicate the originals, because I can.


Thank you for updating your DNS records... now the page is much more informative :D .

Just a quick question, I got the impression, I don't remember from where, that these joints were inserted into the valve body prior to finishing it by (I don't know the English word for that) pressing the remainings end to get the final shape of both ends of the valve. Do you know what kind of material can be used to pass through the valve body without loosing its properties?

Best regards

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