Hw45 power dropping

[martyn]

Hi, I have inherited a early hw 45 in .177, it probably dates from the late 80's, it was tuned by venom when they were at trapshot, as far as I can see all they have done is put spring guide to other end. The problem I'm finding is power dropping around 100 fps over 15-20 shots, stripped it and found piston really tight in tube. So put it in lathe took some off piston seal ( standard white one) now it falls under its own weight. Was running nice for a while but now has dropped 100 fps again, does anyone know if the seals get worse with age.

[Shed tuner]

Get one of the ausie red seals, much better than the crappy hard white one. If it falls under it's own weight, it's too loose.

[TonyL]

Yep, as Jon says, many that have used the parachute seals seem very happy with them.

The problem with the original is that, I believe, they are PTFE? PTFE has no memory and creeps. So, although it's been sized, after some time with the hammering received, the outside diameter is increasing in size, making it a tight fit again.

I'm also wondering if it may be worth replacing the breech seal? If there's an issue there, that could be contributing to hard piston landing, exacerbating the piston head swelling issue?

[martyn]

Yep, as Jon says, many that have used the parachute seals seem very happy with them.

The problem with the original is that, I believe, they are PTFE? PTFE has no memory and creeps. So, although it's been sized, after some time with the hammering received, the outside diameter is increasing in size, making it a tight fit again.

I'm also wondering if it may be worth replacing the breech seal? If there's an issue there, that could be contributing to hard piston landing, exacerbating the piston head swelling issue?

Regarding the piston seal, that was my thinking. Breech seal was replaced but made no difference.

[martyn]

Get one of the ausie red seals, much better than the crappy hard white one. If it falls under it's own weight, it's too loose.

Aussie seal now ordered. Thanks for info.

[averageplinker]

Aussie seal now ordered. Thanks for info.

When you have fitted and tested it please let us know how you get on with it.
Cheers

[PhatMan]

martyn,

+1 on the Aussie seal - I fitted one to my 0.177" HW45 SilverStar, and it has performed flawlessly ever since.

The Aussie seal was a perfect fit to the cylinder, and needed no sizing

Have fun & a good weekend

Best regards

Russ

PS My seals took ca. seven (7) weeks to arrive, so don't worry if they seem to take a time to arrive.