I have used vortex seals in all my guns with good results except for my Hatsan's. I have tryed all the most popular seals and found that the factory molded seal works best. I lost about 100+/- fps with after market seals. If you do a search you will find some good threads on the subject.
Michael, when you topped your gas piston off to 125 bar, did you have to get a gas fitting first? From Hatsan? How much was it? Thanks.
Airguns need a lubricant that can take 3,000-5,000 psi pressure without detonating.Just about all "oils" are a no go. These are no firearms.-Y