Hassan Striker Vortex New Piston Seal, Lower FPS

[Lostcoast]

I just had a Maccari piston seal put in my Hatsan Striker Vortex. The reason for the installation was because the velocity of my Striker had gone down from 750+ fps with CP 14.13 pellets down to around 700 fps. I figured the stock piston seal had gone bad. Unfortunately with the Maccari seal the velocity is now even lower - 661 fps. Will this change as the piston seal gets broken in? If not I may have to have the Vortex ram replaced with a spring...

[rong1966]

My velocity stayed the same. I bought a chrony after I had replaced the seal in my .177 with the ARH one and the velocity seemed lower than it should be, so I put the original seal back in and saw the same numbers.

[OleTomCat]

I just had a Maccari piston seal put in my Hatsan Striker Vortex. The reason for the installation was because the velocity of my Striker had gone down from 750+ fps with CP 14.13 pellets down to around 700 fps. I figured the stock piston seal had gone bad. Unfortunately with the Maccari seal the velocity is now even lower - 661 fps. Will this change as the piston seal gets broken in? If not I may have to have the Vortex ram replaced with a spring...

Did you put the seal in or did someone else do it for you?

It sounds like the seal was not sized correctly to me....

[Lostcoast]

I had it put in by a well-respected airgun tuner, who I think prefers tight-fitting piston seals.. Maybe I should remove it and put a new Hatsan piston seal in.

[Lostcoast]

Someone on the Yellow Forum suggested that perhaps the Vortex ram is losing air. Can these be worked on and repaired? Dang I wish I had a Hatsan fill probe so I could check to see what the current pressure in the ram is.

[rong1966]

Where is the fill port on the Edge gas ram?   I've had mine apart several times and there is a "tunnel " near the end of the ram, but I don't see an opening where the ram could actually be filled.  The better Hatsan models seem to have a fill port but does the Edge?

[OleTomCat]

I had it put in by a well-respected airgun tuner, who I think prefers tight-fitting piston seals.. Maybe I should remove it and put a new Hatsan piston seal in.

If it is to tight or to dry it will be slow.

[mentolio]

I have a similar experience. I just put an ARH seal in my Webley Value Max (total rebuild and lube tune to include a light hone, deburr, thorough cleaning, etc). So now after about three hundred or so shots I Chrony'd it, and found a significant loss in velocity (averaging 60 FPS or so average loss). These seals are oversized, and it seems they need to be "sized." My stock Piston measured 26.8mm diameter, but that is measured off the Piston. The ARH seal (installed on the piston) measured 27.04mm diameter.
I can't even guess how much installing the seal on the Piston increases diameter (or if it even does), so I went a little conservative when sizing the seal down. My final measurement was 26.95mm. Gun shoots, and is still accurate, so I'll throw a hundred or so shots through it before re-chronying, and will report back the results when I do.

[mentolio]

ARH seal versus stock seal diameter:

WHEW! Sorry in advance for the length...

   OK, just found out the difference between an ARH seal (for Hatsan 95) and the stock Webley value max seal (which should take same seal) The ARH is said to be an "oversized" seal, which needs to be sized to the air tube. After I Chrony'd the gun (with the ARH) I found that I had lost pretty significant velocity while also increasing my extreme spread. When I measured the ARH while installed on the piston the ARH seal's diameter was 27.04 mm. I then compared this to the outside diameter of the stock seal while not installed on the piston, which measured out to 26.5. I assumed that the ARH seal must be too big, so I resized it down to 26.95 mm. I put about 100 rounds through the gun, just to ensure that I burned off the majority of the extra lube. When I tested again, I found that my velocity had decreased even more, but my extreme spread seemed to improve somewhat. So I took the piston out again, removed the new seal, and then measured both seals side-by-side uninstalled. What I discovered is that the stock seal is actually is just abit smaller than the ARH as I resized it. Then I measured the old seal installed on the Piston. What I found was that the stock seal expands in diameter pretty significantly when installed (measuring 27.22 to 27.10mm installed, and this seal has chunks taken out of it!), the ARH DOES NOT EXPAND LIKE THIS. Also of note, is that the ARH seal is made of softer material, which may explain the lack of expansion when installed, but I can't be sure. The stock seal however does significantly increase in size. After reinstalling the beat up stock seal, it measured 27.22 mm at its largest, and 27.10 at its smallest. So the lesser velocity appears to not be due to an oversized seal/too tight of a fit/too much friction on the seal (ARH), but instead is because the ARH seal is too small to seal properly. Now I want to say that this is just because of a subtle difference between my Whitley value max and the 95 tube, but I also own a Hatsan 85 (same diameter as the 95). Did the same rebuild with the same ARH seal in the 85, with the same loss in velocity.
   So, if anyone has a new, factory seal they could measure the diameter of, that would be helpful to me. As it stands, I plan on searching for larger diameter seals, and will likely order factory Hatsan seals in the meantime.

I will post all my numbers when I can. Can't figure out how to post a PDF?!?

[Gut2Fish]

When doing my tune ordered the seals from Australia of all places. Funny thing was it was cheaper to get the seal there and shipped halfway around the world than order a new seal here in the states. The piston seal from Custom Air Seals is oversized. Very snug fit but left it as is to wear in the gun. You could literally hear the suction when cocking. Took a few hundred shots for it to completely smooth out. A darn good seal, gave more power than when the gun was new and did the tune due to the dramatic loss of power from stock seal after maybe 600 shots since new. Purchased a breech seal at the same time. These are way too big and must be sized for length. Made the mistake of putting in breech as is resulting in dramatic barrel drop. Needs a lot of sanding and suggest if you get a breech seal there to use old one as reference to depth prior to installing it. Couldn't get the new one back out without tearing it so had to sand the top down to near flush. 

https://www.customairseals.com/

Very happy with the 125 replacement piston seal.