Gamo g-magnum 1250 Mach 1 transfer port

[soldier_hr]

Hi!
I have bought my rifle from one Portugal online shop. I did not know that Portugal have power restrictions for air rifles so my rifle had only 24 joule power. Power restriction was only on transfer port (tiny hole) , inside the rifle piston and gas ram is the same as the full power version so i drilled 3.5mm hole and got power increase. Does anyone know what is maximum transfer port size for this rifle?

[soldier_hr]

This is how port looked before drilling:




and after



 45 joules model transfer port hole look like this:



To get 45 joules do i need wider transfer port or 3.5mm is ok? Am i loosing some power because transfer port hole at the end is wider than pellet diameter (.22) ?

[Vampp]

I think some recommend 40mm transfer port hole.
I am not sure about this tough.

In case you want to buy a swarm magnum ( magnum 10 replay ) , you can head on to the guys at royal.si they shipped it to me full power ( factory new , no drill ).

[Roadworthy]

I read somewhere awhile back that three millimeters is about the optimum size for a transfer port.  At some point beyond that your power will go down.  Of course once you've done the drilling you can't put the material back very easily.  Proceed with caution.  I do not know the maximum power capability of your gun.  I do know there are more limitations than just the transfer port.  The swept volume of your compression tube will be a limiter as well.

[Vampp]

I read somewhere awhile back that three millimeters is about the optimum size for a transfer port.  At some point beyond that your power will go down.  Of course once you've done the drilling you can't put the material back very easily.  Proceed with caution.  I do not know the maximum power capability of your gun.  I do know there are more limitations than just the transfer port.  The swept volume of your compression tube will be a limiter as well.

I found a guide I received from mundillar a while ago.
38 mm whole they recommend , other sites 40mm .

In case someone needs this I attached it with PDF.
It's the entire guide I have.
As a note I did not do this , so it's a tip I received form the guys from Portugal.

But again , as a european ,  I recommend you to buy it from rojal.si , they are from Slovania and they really have limits to guns there , especially air rifles ( lucky them ).
The rifle from them will come with no limits ( make sure you ask them , they offer downgrade service ).

[OleTomCat]

Typically no more than 76% of the bore size for the transfer port is Ideal for a .177 that is 3.15mm.

[Albertus]

To get 45 joules do i need wider transfer port or 3.5mm is ok? Am i loosing some power because transfer port hole at the end is wider than pellet diameter (.22) ?

I am afraid that neither the 4.0 mm diameter transmission port will be sufficient to obtain hypothetical 45 joules, nor will the IGT gas spring pressurize even further. It's all just a good marketing ad. 

Airgun Rifle (GAMO) G-Magnum 1250 Mach 1 has a work cylinder 25 x 120 mm with a volume of about 80 cm3 - this corresponds to a maximum power of 32 to 36 Joules, which is commonly achieved by other renowned world manufacturers Airgun Rifle - eg. Diana 350 Panther, Hatsan 125-130-135 etc ... 

Just for the power of 45 Joules would inevitably have to increase the volume of the compression cylinder. Perhaps, however, Gamo has already prepared some "Supersonic-Magnum 1500"!?? According to my calculation, the working cylinder would have to have at least 32 x 125 mm with a volume of about 100 cm3! But who would then be able to stretch such an Airgun Rifle? 

[Albertus]

Manufacturers of Spring Airguns Rifle compete in marketing promises of supersonic speeds and real hard to reach performance. But Gamo is number one, with her "Mach 1" ahead of everyone! 

However, with the GAMO G-Magnum 1250 with a standard 160 Atm Gamo IGT gas spring, it is not usually possible to achieve more than 30-32 Joules. This is for cal. 22 Sufficient!
However, for power outputs of 36 Joules and maybe up to 40 Joules, we also need a gas spring with a higher pressure of 180 to 200 Atm.

I do not want to advertise here, but only the reinforced “Megapower VD” (200 Atm) or “Gigapower VD” (220 Atm) gas springs from Vado123 will meet this requirement. … 
       
   

In addition, these gas springs are equipped with a drain valve so that the pressure can be adjusted to the required value and the size of the transfer port optimized for the entire Airgun system.

[gibawatts]

What I learned was quite the opposite. If you have more power, you need to close the hole. There are some shops selling the the version with no holes for full power. It's restricted to install it here in Germany but we can buy it freely.

[Albertus]

However, too much power of the gas spring will not only cause a large recoil, but a heavily constricted small transfer port causes multiple piston bounces from the air cushion at the bottom of the compression cylinder and the reverse (forward) and vibration of the weapon.

This worsens the shooting accuracy and destroys your optics!

Therefore, it is necessary to reduce the pressure of the gas spring according to the allowed limit and optimize diametr the transfer port. 

[gibawatts]

However, too much power of the gas spring will not only cause a large recoil, but a heavily constricted small transfer port causes multiple piston bounces from the air cushion at the bottom of the compression cylinder and the reverse (forward) and vibration of the weapon.

This worsens the shooting accuracy and destroys your optics!

Therefore, it is necessary to reduce the pressure of the gas spring according to the allowed limit and optimize diametr the transfer port. 

Does the FAC Gamo rifles with IGT rams has the holes?

[Albertus]

If I follow the questions in the discussion forums, I understand that Gamo is exporting its Airgun Rifle to many countries, but the „GAMO G-Magnum 1250“ in the version "IGT Mach 1" version with full power of 45 Joules seems to have no one yet.

Everywhere, in almost all countries, there are some restrictive measures!

Also in Spain, only 24 Joules power is allowed, so no one knows the correct hole size for trasnfer port. Also the supplied IGT gas spring has insufficient pressure and low force! …   

[gibawatts]

I disassembled my Roadster yesterday and couldn't find a transfer port. The piston is closed and, unfortunately and I don't know why, the writings on the gas ram were scratched out so I could not identify the model. Here in Germany we are limited to 7.5 joules, so I guess the power is limited by the weaker gas ram.

[Albertus]

I see, but you still have a sense of humor! … So some transfer port must be there, I don't believe they would forget to drill it. Have you ever tried to fire your rifle?

Can you somehow verify the diametr the hole of transfer port your Airgun Rifle? Please try to measure it at least approximately….

[OleTomCat]

I think some of you are confusing the holes....

The transfer port is where the air goes from the compression chamber to the barrel, for Gamo break barrels that's right in the breach where the breach seal is located.

The FAC restriction hole is actually in the piston it's self allowing air to bypass the piston as it slams forward...

Some restricted guns use a longer piston instead of a leak hole.

[gibawatts]

I think some of you are confusing the holes....

The transfer port is where the air goes from the compression chamber to the barrel, for Gamo break barrels that's right in the breach where the breach seal is located.

The FAC restriction hole is actually in the piston it's self allowing air to bypass the piston as it slams forward...

Some restricted guns use a longer piston instead of a leak hole.

That's it, I was mistaking the holes 

I saw some videos with the guys cementing the piston hole and getting 40% increase in FPS.

[Albertus]

What is it FAC ... ?? FAC - Firearms Acquisition Certificate   

Gamo the holes on the piston have not been drilled for a long time! The transfer port is constricted!
And the piston rod extension is used in airguns Diana ...

[canadian_shooter]

To get 45 joules do i need wider transfer port or 3.5mm is ok? Am i loosing some power because transfer port hole at the end is wider than pellet diameter (.22) ?

I am afraid that neither the 4.0 mm diameter transmission port will be sufficient to obtain hypothetical 45 joules, nor will the IGT gas spring pressurize even further. It's all just a good marketing ad. 

Airgun Rifle (GAMO) G-Magnum 1250 Mach 1 has a work cylinder 25 x 120 mm with a volume of about 80 cm3 - this corresponds to a maximum power of 32 to 36 Joules, which is commonly achieved by other renowned world manufacturers Airgun Rifle - eg. Diana 350 Panther, Hatsan 125-130-135 etc ... 

Just for the power of 45 Joules would inevitably have to increase the volume of the compression cylinder. Perhaps, however, Gamo has already prepared some "Supersonic-Magnum 1500"!?? According to my calculation, the working cylinder would have to have at least 32 x 125 mm with a volume of about 100 cm3! But who would then be able to stretch such an Airgun Rifle? 

 The Gamo Magnums in North America have a 33mmx130mm compression tube.

[Albertus]

...  The Gamo Magnums in North America have a 33mmx130mm compression tube.

 

Well that's really SUPER! Put some photo of this giant cannon Gamo "MAGNUM Canadiens Mach 2" !!

[Albertus]

Yeah, dear gentlemen, when you buy an air rifle, do not spare and get a real Air Cannon!