Handpump filling problems Sumatra .25 carbine

[sammeke]

Hey guys, I already searched on GTA about this problem, apparantly I am not only one who has issues with filling his Sumatra…
Purchased a new carbine in .25 cal today and it was filled  to 180 bar.
I handpumped it to 200 bar at home and when I opened the bleed valve of my pump all the air of the gun was coming out through the bleed valve of the pump…
Tried bleeding off the air of the pump very fast, didn’t work…
Tried filling the gun in a vertical position, didn’t work…
The shop will take the Sumatra back and give me a new one but if I understand it correctly also the new one will have the same issue with the handpumps?
I really like the cheap China pumps, they are simple and give me a good workout, and use nothing else for filling my PCP’s.
I know that a tank with a quick push bleed valve would probably solve the issue but I would prefer to stay with my handpumps.
Any ideas?

[Robert 5mm]

Sounds like the check valve on the gun is open

[Habanero69er]

As Robert said. Check valve stuck sounds right.

[Back_Roads]

 Try a couple drops of pure silicone oil in the fill nipple that may free up the sticky fill valve.

[sammeke]

Thanks for the comments, just delivered the gun back to the shop , fingers crossed that it will work with the new Sumatra….

[Habanero69er]

Even though you’re getting a new Sumatra, it’s not a bad idea to use a little pure silicone like James suggested. Especially when you’ve put the effort into hand pumping.

[Madd Hatter]

I have the same problem with my Sumatra. The pressure needs to be released fast for the valve to seal. I got a new fill station off eBay and it did the same thing. The hose is too small to release the air quick enough. I've been thinking about installing a one way male Foster fitting but the original fitting will need to be cut off and then drilled and tapped for a 1/8 npt. I don't think I'll be doing that anytime soon as all I have to do is use my other fill station.

[Habanero69er]

Will Piatt, God rest his soul, installed a Foster fitting on my .25 carbine. Never had an issue. Knock wood.