Hatsan Flashpup regulator tuning questions.

[JohnnyPneumonic]

I recently installed a Huma regulator into my wooden flashpup. Standard plenum size, not the XL.

I've been seeing guys getting 830fps with 25.4 grain pellets with the reg set to low pressure like 120 or 140 bar, and the hammer spring only a few turns out from home.

I was able to average 825 on a 10 shot string before regulation, but have not been able to get that speed from the regulator at any settings.

Any thoughts or ideas?

 

[Vetmx]

Did you open up your ports?

 

[JohnnyPneumonic]

Nope! Is this an essential step? I've got a mechanical background and a drill.

 

[Vetmx]

Turning an unregulated gun into a regulated gun is not as simple as just slapping a reg in it. A unregulated gun has small ports because that is its regulator. A unregulated gun has a heavy hammer and spring because it has to crack the valve at the original max fill pressure. Or close to it. So when you put a reg in one of these guns, there are still three things that are still wrong because they belong in an unregulated gun.

 

[Vetmx]

You should be able to use the stock spring and hammer and still have adjustability to tune it. Unfortunately you are going to have to set the reg at 150b. But since you seem to be craving power, you know what comes with that, low shot count with a small air tube. And now smaller since you stuck a reg in there. Port your gun but don’t go over 80% of the caliber. If your gun is a .25, go with 5mm porting if the components will allow it.

 

[Vetmx]

Don’t expect many shots. I did a .22 Flashpup for a friend and it only gets 2 mags.