gamo g-magnum 1250 IGT MACH 1 transfer port size

[wildscorpion]

Hi!

Can anyone tell me what is the diameter of transfer port for full power version (45j) of this rifle? I bought my rifle online and got reduced power version so i drilled my transfer port to 3,5mm (1.37795 inch) but still i dont have full power like original 45j model. Is now my hole bigger than it should be or i need to drill a bit wider hole? 

this is my gun before drilling:

this is after drilling :

and this is how transfer port looks on original 45j model :

Am i loosing some power because my exit hole (just under barrel breech) is bigger than diameter of transfer port hole and it is not parallel with barrel breech like in original 45j model??

 

[John "spysir" Blount]

Never seem that modle and other parts might be different as well? Were it a diana I'd think your just a bit too large o the port, maybe fill it in and carefully start drilling again?

Some thoughts:

https://www.tapatalk.com/groups/yellow/working-on-rws-diana-transfer-port-size-some-preli-t103161.html



John

 

[wildscorpion]

Thanks for reply John. My other parts are the same as at full power version (piston does not have hole in front and gas ram is the same version 40450 as in full power version) so the power was reduced only by the smaller transfer port diameter. As far as i know Gamo IGT MACH1 have 33mm cylinder so there is more air to compress than in other brands of air rifles so wider transfer port is needed. I read it somewhere that optimal hole diameter for this model is 3.8mm (0.14960629921) but before i start to drill again i want to be sure about that. I forgot to mention that i have .22 version of the rifle.

 

[JoeKool]

PM me? I have a working full power version of that same model Gamo that I am willing to sell. Not used often, and is in fair condition. You could use it as is or use it for parts. Again if interested PM me?

Joe Kool

 

[wildscorpion]

PM me? I have a working full power version of that same model Gamo that I am willing to sell. Not used often, and is in fair condition. You could use it as is or use it for parts. Again if interested PM me?

Joe Kool

Thanks for the offer Joe. I could sold my gun and buy full power version if i wanted. Restoring full power on my gun is a challenge so i want to achieve that. Second gun for me will be PCP.

 

[JoeKool]

PM me? I have a working full power version of that same model Gamo that I am willing to sell. Not used often, and is in fair condition. You could use it as is or use it for parts. Again if interested PM me?

Joe Kool

Thanks for the offer Joe. I could sold my gun and buy full power version if i wanted. Restoring full power on my gun is a challenge so i want to achieve that. Second gun for me will be PCP.

Got it, good luck!

 

[Evilivan]

Hi, 

Sorry for the thread resurrection.

I have the same restricted gun bought in Portugal. Guys from the store told me that the optimum port width is 38mm, and 40mm max. I can send you the guide...

I have a question regardless, knowing the width,h deep should I drill the port?

 

[Hobbyman2007]

I hope you meant 3.8mm to 4 mm. I really don’t think the transfer port is the way they reduced the power . I would be willing to bet that the gas ram installed even though it has the same part number has a lower fill pressure or it has leaked slightly . The other thing to look at would be the catch on the piston , could very well be that the stroke has been shortened . 

 

[Evilivan]

Yes, 3.8 to 4.0 mm

The shop guy told me that the power reduction is only due to port size, everything else should be the same 

 

[Alfonsmucha666]

Hi, I drilled 4mm, speed is only 250m / s. I have a new seal. Where will the error be? I have a piston at 160 bar. But it has leaked slightly? Thanks for the reply

 

[JackSparrow]

Hi Alfons,

Is there a solution or any news to your endeavour?

May it be that 4mm is just alightly to big?



Thanks Jack

 

[Sniper_Tom]

…”Hi!

Can anyone tell me what is the diameter of transfer port for full power version (45j) of this rifle? I bought my rifle online and got reduced power version so i drilled my transfer port to 3,5mm (1.37795 inch) but still i dont have full power like original 45j model. Is now my hole bigger than it should be or i need to drill a bit wider hole?”... 





Hello wildskorpion !



This is a futile effort! In Spain, the Airguns Rifle "Gamo G-MAGNUM 1250 Mach 1" is sold only with a reduced output power of 24 Joules and also with a weaker gas spring IGT - 160 Atm. Also, the transfer port is a little strangled - I estimate that the diameter of about 2.4mm. However, with this IGT gas spring (160 Atm / 80kg) it is possible to achieve an output of about 30-32 Joules, but larger values are probably not!



I'm afraid it is not enough to just drill a larger hole in the transfer port, but it is also necessary to increase the spring force. For Airguns G-MAGNUM 1250, enhanced pressure springs from Russian manufacturer Vado 123 are sold on eBay :



”Premium VD” - 180 Atm / 90kg … transfer port cca 3,2 mm - 36 Joules

“Megapower VD” - 200 Atm / 100kg … transfer port cca 3,5 mm - 40 Joules

“Gigapower VD” - 220 Atm / 110kg … transfer port cca 3,8 mm - 45 Joules

However, it should be noted that this result can only be achieved at the cost of an extreme increase in gas spring pressure to 200 to 220 Atm, as well as excessive stress on mechanical components, increased recoil and lower accuracy of firing and airgun life. Personally, I would not recommend increasing the power to 45 Joules much.

Optimum performance 36 Joules Airgun "Gamo G-MAGNUM 1250" with a compression cylinder 29 x 120 mm can only be achieved with a perfectly balanced gas spring mechanism with an optimum pressure of approx. 170 Atm / 85 kg.



These gas springs from Vado 123 also have a drain valve so that the pressure can be adjusted to the required value. By mutual varying the transfer port size and the spring pressure, an optimum balance of the entire pneumatic system mechanism can be achieved.


Best regards
Sniper Tom

 

[Sniper_Tom]

No more unnecessary speculation!
It's alright ?

 

[Sniper_Tom]

Optimal Pressure and Force of Gas Ram Spings for Airgun Rifle GAMO G-Magnum 1250



Of course, all efforts to increase performance by modifying the Transfer Port and using a stronger spring - borrowed from the "truck suspension" or the (much sought after) "Mega" and "Giga" gas springs only lead to the creation of a digging monster that is no longer easy to stretch.



It also has a disastrous effect on shooting accuracy and optics life!



Therefore, I recommend increasing the Transfer Port to the optimal value - diameter approx. Ø 3.2 mm and then reducing the pressure or spring force to set the allowable limit - eg 12 fpe (16 Joules) / United Kingdom of Great Britain /.




.
For the G-Magnum 1250, Gas Spring with a drain valve from company Vado123 from eBay or AirGunUp are ideal (… these can be repressurized with air or inert gas at any time).

 

[Sniper_Tom]

OK?
By analogy with regulations - permitted AirGuns power limits valid in other countries (7.5-12-16-20-24 Joules) - other values for power settings can be derived by conversion, according to the known simple algorithm , by reducing the gas spring pressure (Gas Ram) or force for a conventional coil steel Spring.



Of course, everything after measuring and verifying the optimum of the specified type of AirGun Rifle.

 

[Johny_great]

There ate two things u have to do to achieve original 45 joules.

1. widen the t.p.hole 3.5 to 3.8 mm.

2. Surface of the breach seal should be flat as in original. But limited version has a wide carved hole in which the 2.x mm t.p.hole is set. The carved gap should be filled and then work on t.p.hole...

 

[Sniper_Tom]

Hi Johny_great!

Thanks for the valuable advice! However, the recess in the Transfer Port hole does not have such an effect on the performance, after all, there is another cavity in the pelet's skirt that has an effect on the compression!

As far as I know, no one with the original Gamo IGT gas spring has yet managed to achieve the declared marketing value of 45J. Usually it ends at 32J to 36J because these springs are only pressurized to 160bar (Atm) for export.
It is necessary to pressurize to a higher value…

180 bar … transfer port cca 3,2 mm - 36 Joules

200 bar … transfer port cca 3,5 mm - 40 Joules

220 bar … transfer port cca 3,8 mm - 45 Joules

 

[Johny_great]

thank u tom.

U have a great knowledge on it. Thanks for sharing.

 

[Tommy81]

hello my name is thomas, looking for information i read that you were trying to reach 45 joules with your gamo 1250, did you succeed? can you give me some advice? because I have the same problem, I bought it on the internet and how to get 45, in reality it is only 15 joules, I like you have 5.5 thanks I hope you can help me.

 

[Tommy81]

hello my name is thomas, looking for information i read that you were trying to reach 45 joules with your gamo 1250, did you succeed? can you give me some advice? because I have the same problem, I bought it on the internet and how to get 45, in reality it is only 15 joules, I like you have 5.5 thanks I hope you can help me.