Tuning Vortex Type-2 air piston question

[gxs]

Hey

I'm new here so I apologize in advance if I have missed the topic but this seems as good of a place as any to ask.

A little backstory first... I started shooting targets when I was 6 with my grandfathers rifle and then switched over to bows. Then by some divine miracle (my wife calls it a curse) I received two air rifles. I got into it and now I own two more (along with 2 BB guns and 2 pellet pistols because four is a magic number or at least that what I'm telling everyone). Did I mention I risk sleeping on the couch daily?

So the last rifle I have purchased is a Hatsan Mod 130 (not QE but the old model). I love it but it's a little weak for my taste. It has a Vortex piston that I can fill using a PCP air pump but here's the problem... The older models had a release screw to release the pressure but my gun only has a cutout for one and no screw. Another problem is that someone on youtube recommended releasing all the air and pumping new one as you don't know how much is in it so that you don't overdo it. But that's not logical as pumping air in should in theory at least show me how many PSI I'm at.

So I need someone that know about Vortex pistons to chime in. How do you know how much is in and how do you bleed them if needed.



Cheers and sorry for the long winded question

 

[SteveP-52]

Handpump (you can usually find inexpensive 4500psi handpumps on Amazon), Hatsan fill probe and an 1/8"BSPP female adapter to plug the probe to the fill hose: 

https://www.pyramydair.com/product/air-venturi-replacement-probe-fits-select-kral-arms-evanix-hatsan-guns?a=3985

https://www.pyramydair.com/product/air-venturi-male-quick-disconnect-1-8-bspp-female-threads-steel-rated?a=3550

Start pumping and just watch your gauge. If memory serves, the 130 should have something like 135 bar in it, so just pump until you hit that mark

With no screw, there is no way to bleed it off that I know of unless Hatsan wants to be nice and tell you how...lol.

 

[gxs]

Thanks for the answer but I do have a pump and the probe ordered. What is confusing me is this video:

https://www.youtube.com/watch?v=EZb7Es9Ypck&t=293s



It states there that you don't know the pressure due to a one way check valve and that you have to let the gas out. Or have I misunderstood the video which is always an option.

My piston states a max range of 160 so I was planing to just stick the probe in and do a few pumps to equalize and get a reading and then go to 145 or 150 to be safe but the video makes me feel that I wouldn't get a proper readout. Either that or I have misunderstood completely.



Also thanks for the help. I have browsed the web quite a bit but it seems that there's a few revisions out there and I just don't want to order a new pump so soon.

 

[SteveP-52]

Would help if you had a chronograph to know what kind of fps numbers you're getting before you start adding air but not a deal breaker. If I'm understanding him, he prefers to completely bleed the ram but he also has the bleed screw in his. You don't have to, just pump until you hit the psi number you're aiming for. Might take you a couple days to get a reply but you might try emailing HatsanUSA and ask what the factory pressure for the ram is to start. https://hatsanairgunsusa.com/contact-us/

If they tell you it's 135psi, pump to that and again, the gauge will tell you where you're at while filling. Shoot the rifle for a bit to see what you think and then add 5 psi at a time until you have it at the power level you're wanting. It'll take you a bit longer but you won't risk filling it higher than you might want since you don't have a way to bleed off any overfill.

Another point to remember is the higher you fill it, the harder the cocking effort and recoil will get.

 

[dv8eod]

You should be able to slowly bleed out any air with the handpump by pressurizing just enough to open the ram valve, and then cracking the bleed screw on the pump to let it leak out. It works with PCPs that need to be drained, I don't see why that same technique wouldn't work with the ram.

 

[SteveP-52]

My 95 had the bleed screw so I didn't have to consider trying it. Supposedly, that valve is one way only so honestly can't say if it will work or not but go for it and if it does, you just added a pretty big one to the Hatsan gas ram knowledge base.

 

[gxs]

Thanks guys

I'll tinker with the valve a bit once the pump arrives and see if I can open it. As I've said there's lots of conflicting information about it. Some say that you need to equalise the pressure and face the piston downwards once the valve opens. And some say that it's a one way valve.

I'll try the first method just to see if it works and report back and I'll definitely refill the piston as it's probably holding at about 90 at most at least based on the power and ease of cocking.



I'll report back in a month or two when the pump arrives (stocks are low for everything that has to do with air rifles including rifle parts and bluing liquid).