Help with my new Gamo PX-40

[ShadyG]

Hello everyone, I'm new here, and to PCP rifles, and I'm looking for some help. I've just bought (yesterday) a Gamo PX-40, having read all the glowing reviews on it, but it's not acting like I'd hoped. I've been using the pump that came with it, and pumping it up to full, but I'm only getting about 20 rounds out of it before the pressure falls away, and the pellets start dropping by a long way as well. Everything I've been told about this rifle says I should get 120 - 130 shots out of it on a full charge.
I'm following all the instructions from the book and from websites, and I'm wondering what I'm doing wrong.
I've been a shooter all of my life, mainly .22LR, so I'm fairly experienced in the general dynamics of shooting.

 

[Joedirt199]

You get a full power one? The only ones I can think of that would have a higher round count would be 12 fpe .177 limited guns. Gamo GX-40 is the same thing as a Gamo Urban.

 

[ShadyG]

I had to show my fire arms license to buy it, (I'm in New Zealand). It takes 230bar which is a lot of pumping, but the pressure drops off considerably with the first 20 shouts.

 

[Neu]

I had to show my fire arms license to buy it, (I'm in New Zealand). It takes 230bar which is a lot of pumping, but the pressure drops off considerably with the first 20 shouts.

Do you have a chronograph to see what fps your getting? Have you filled the gun with air and let it sit to see if it has a leak somewhere? If it's a full power rifle then it may have the hammer spring close to max and that would account for the low shot count. My urban is set at 750 fps gets around 35 good shots and is basically the same rifle.

 

[Scotty1]

I would get 3-4 mags from mine 750-800 or so.

 

[ShadyG]

I don't have a chronograph, and I will fill my gun and watch it to see if I've got a leak. It's brand new though, should I expect a leak? the bolt is quite hard to pull back, and I don't know if that's got anything to do with the hammer spring. (I have absolutely no experience at all with this type of rifle, so be gentle if I don't seem to know what I'm talking about.)

 

[Struckat]

Read the manual about hammer spring adjusting. That is the place to start if it holds air.

Get a $30 speed meter. They work very well.

 

[Neu]

I don't have a chronograph, and I will fill my gun and watch it to see if I've got a leak. It's brand new though, should I expect a leak? the bolt is quite hard to pull back, and I don't know if that's got anything to do with the hammer spring. (I have absolutely no experience at all with this type of rifle, so be gentle if I don't seem to know what I'm talking about.)

Here is a vid on how to adjust the hammer spring, it on a urban but it will be the same for the GX 40. The bolt will get harder to pull back the more tension that is on the hammer spring.

 

[MBG]

The GX 40 is the urban with a longer barrel, If its hard to cock then the hammer spring is too tight, you need to back it out a few turns... With the slightly longer barrel you would be able to get a good 750 - 800 FPS at a slightly lower hammer spring setting than the Urban...

 

[ShadyG]

Here is a vid on how to adjust the hammer spring, it on a urban but it will be the same for the GX 40. The bolt will get harder to pull back the more tension that is on the hammer spring.

Thanks, that's fantastic. I'll have a go at that as soon as the boss releases me from domestic duties.