Velocity Loss ?

[Mark 611]

Like I said before, these rifles are not power houses to begin with, ARH kit for these rifles are probably OEM power? Like Ed said many factors can cause this, I would look at ur piston seal fit, and check ur breech seal, even tho they my look good? how does the piston seal fit? is it tight or lose? if either condition exist it will cause velocity loss, also the spring has probably settled in, I would try to add a 1/8th or 3/16th'' spacer on top of ur top hat as well, but I think ur piston seal fit is ur problem, if all is well there u may have a bigger problem

[Oldgringo]

The piston seal is very tight in the chamber.  The breech seal passed the "tissue" test. Neither would snag a tissue when softly swiped across/around them.  I dunno', it's beyond my level of understanding.  I'm gonna' look for some delrin washers and see if they'll help.  ITMT, I can hit my spoons and spent shotgun shells at 25 yards with regularity using CPHP'S at the slower velocity.  So, why fret?  If I didn't have a chronograph, I wouldn't even know she had slowed down.

Happy Independence Day,  y'all!

[Airnut]

The piston seal is very tight in the chamber.  The breech seal passed the "tissue" test. Neither would snag a tissue when softly swiped across/around them.  I dunno', it's beyond my level of understanding.  I'm gonna' look for some delrin washers and see if they'll help.  ITMT, I can hit my spoons and spent shotgun shells at 25 yards with regularity using CPHP'S at the slower velocity.  So, why fret?  If I didn't have a chronograph, I wouldn't even know she had slowed down.

Happy Independence Day,  y'all!

That may be your issue! As Mark has stated. The piston may be to tight in the bore. If it is a new seal it should loosen up after a few hundred shots. I have found that 3 to 5 lbs.of force to move piston in the bore works best for me. If the gun is doing what you want don't worry about it and have fun if not then resize the piston seal.

[Oldgringo]

Like I said before, these rifles are not power houses to begin with, ARH kit for these rifles are probably OEM power? Like Ed said many factors can cause this, I would look at ur piston seal fit, and check ur breech seal, even tho they my look good? how does the piston seal fit? is it tight or lose? if either condition exist it will cause velocity loss, also the spring has probably settled in, I would try to add a 1/8th or 3/16th'' spacer on top of ur top hat as well, but I think ur piston seal fit is ur problem, if all is well there u may have a bigger problem

That's the piston seal that was in the gu when it was shooting 670 fps in 2016.  I think it might be the original and it is very tight.  Why would it grow fatter?  I'll tear her down again and change out the piston seal.  Where do you get the Australian seals?

[Airnut]

Like I said before, these rifles are not power houses to begin with, ARH kit for these rifles are probably OEM power? Like Ed said many factors can cause this, I would look at ur piston seal fit, and check ur breech seal, even tho they my look good? how does the piston seal fit? is it tight or lose? if either condition exist it will cause velocity loss, also the spring has probably settled in, I would try to add a 1/8th or 3/16th'' spacer on top of ur top hat as well, but I think ur piston seal fit is ur problem, if all is well there u may have a bigger problem

That's the piston seal that was in the gu when it was shooting 670 fps in 2016.  I think it might be the original and it is very tight.  Why would it grow fatter?  I'll tear her down again and change out the piston seal.  Where do you get the Australian seals?

Huum! The only thing that I can think of that may swell the seal is maybe the lube used?? I guess it's possible if someone used some weird chamber Lube?? I would look really hard at the compression tube for any possible issues.(out of round etc.)
You can get the seals at custonairseals.com

[Mark 611]

Ebay sell Custom air seals from Australia, these are good seals I have 1 in my HW30!

[Yogi]

Ebay sell Custom air seals from Australia, these are good seals I have 1 in my HW30!

I understand that they tend to run large or XL.  Did you have to size them down?

-Y

[Mark 611]

No!!!! mine fit perfectly in my 30! but I bought the green eco seal! just to try them out, these are very good seals,

[Airnut]

Ebay sell Custom air seals from Australia, these are good seals I have 1 in my HW30!

Amazon has them also.