Gamo Magnum Gr .25 cal questions

[Odins_Mercy]

Hello first post here.
I got the Gamo Magnum GR .25 cal and was wondering of the Schematics are around here or if someone else knows some questions....

I was curious on what spring could be used to replace the "default" one, and the piston seal on custom air seals Australia, would that also be compatible with this rifle? It says suitable for all 33mm pistons by gamo but ya never know. I'd like to rebuild it with some better quality bits if possible

Or, is Gamo usually kind of......picky about what info is let out? Its been rough finding things thay fit this exact Gamo rifle lol.

[A.K.A. Tommy Boy]

Hi Mike.

I hope that you get your questions answered soon.

I have the Gamo Magnum GR in .22 cal. so I am interested in the answers to your questions too.


Best Wishes - Tom

[Odins_Mercy]

I hope so  I've sent around 1000 rounds through it. Used Air Venturis Moly metal 2 metal on everything the directions said, learned about screws and loctite 242, I also put some dense Styrofoam in empty sections of that stock and filled void spaces, got less buzzing and more of a solid firing going on. I read someone did that hear with rags a while ago.

Before I found this forum though I mightve treated this like a real gun and caused some diseling. Smoke and all coming from barrel. Burnt smell, cleaned it out with simple green hd and wiped and patched until clear and cleaned the barrel again with a dry patch worm, and used this Break Through oil a drop or 2 on a cotton patch and went in and out a few times.

Diseling and smoke went down significantly but from what I'm reading I may have over done it in piston areas and it's migrated upwards.

Glad I found this site 🙌  I don't think it's lost power despite my mistakes lol.

Hi Mike.

I hope that you get your questions answered soon.

I have the Gamo Magnum GR in .22 cal. so I am interested in the answers to your questions too.


Best Wishes - Tom

[Roadworthy]

It appears OleTomCat is back with us.  It appears he won't be doing any tuning for a bit as he gets situated in his new house but he may be willing to answer questions.  He's the resident Gamo expert.  You could try shooting him a pm.

[Odins_Mercy]

That's funny cuz I found out he was a Gamo Guru, emailed him, THEN I found out he was back haha today ha.

Hopefully it works out

It appears OleTomCat is back with us.  It appears he won't be doing any tuning for a bit as he gets situated in his new house but he may be willing to answer questions.  He's the resident Gamo expert.  You could try shooting him a pm.

[Toxylon]

I wouldn't use CAS seals in a magnum gun like the Gamo Magnum. They have been a total bust in my 350 Mag. The CAS seals are quite soft, and that is indeed their claim to fame, but the manufacturer doesn't realize magnum springers need pretty hard seals to work properly. Soft seals in these guns act as breaks in the piston thrust.

A funny truth in springer tuning is that while aftermarket mainsprings are almost invariably massively better than factory springs, with seals it's not nearly so clear cut. The big guns almost always shoot better, as in a couple hundred fps faster, and with better consistency, with the factory seals, provided the seals are sized to fit the chamber and kept intact through the assembly, meaning deburring the receiver before attempting piston insertion.

When I started to tune my Hurricane 1250 (later made by Gamo and the direct wood-stocked predecessor to the current Gamo Magnum), I knowingly bought a Gamo 29mm piston seal* and sized it to fit my gun's particular compression chamber.

*the "33mm Gamos" are 29mm guns by any other manufacturer's / tuner's definition. They use a 29mm piston seal, in a 29mm chamber.

[Odins_Mercy]

Thanks for the info. That makes sense. So stick to OEM basically. Since I apparently need an FFL to get Gamo Piston seals idk lol. They stopped emailing me after I asked for the part number and schematic lol!

So essentially 33mm is 29mm, 33mm seems to be the marketing tool. I would post a link but can't fornsome reason. I found a Gamo Seal that's 33mm that fits "ORIGINAL PISTON SEAL  33 MM

BLACK FUSION
 
BLACK KNIGHT

BLACK BULL

SUPERMAGUM GAMO

- G-MAGNUM 1250
- BM IGT MACH -1
- CAZADOR GRIZZLY 1250
- WHISPER IGT MACH 1"

On ebay item number 185820955367 if you have time to look that up.



I wouldn't use CAS seals in a magnum gun like the Gamo Magnum. They have been a total bust in my 350 Mag. The CAS seals are quite soft, and that is indeed their claim to fame, but the manufacturer doesn't realize magnum springers need pretty hard seals to work properly. Soft seals in these guns act as breaks in the piston thrust.

A funny truth in springer tuning is that while aftermarket mainsprings are almost invariably massively better than factory springs, with seals it's not nearly so clear cut. The big guns almost always shoot better, as in a couple hundred fps faster, and with better consistency, with the factory seals, provided the seals are sized to fit the chamber and kept intact through the assembly, meaning deburring the receiver before attempting piston insertion.

When I started to tune my Hurricane 1250 (later made by Gamo and the direct wood-stocked predecessor to the current Gamo Magnum), I knowingly bought a Gamo 29mm piston seal* and sized it to fit my gun's particular compression chamber.

*the "33mm Gamos" are 29mm guns by any other manufacturer's / tuner's definition. They use a 29mm piston seal, in a 29mm chamber.
[/quote]

[OleTomCat]

I used the Gamo CAS 33mm seals back a few years ago, I had to cut the V shape button off of the top of the piston and then drill and tap with a flat head SHCS to install the seal, I don't know how they get them on at the factory but I could not get the seal to go over the button.  The gun shot violently with the stock spring and my customer, Kevin Grimes, wanted a smother shooter so we cut about 4 coils off of a new spring from ARH and that tamed it down some.

The seals from ARH and CAS are better quality than anything Gamo ever produced back then, I haven't used any of CAS seals in over two years so I can't attest to what they are like now.  The key to getting the softer seals to work is using the proper lubrication after they are sized to the bore.