Seal fit ?

[kiwi]

Hi..How meany thou over size should a seal be compaired to the
compression tube dia for the correct fit..

thanks
Pete

[airiscool]

Pete,

I've wondered about that also. Maccari mentions how to re-size on his website, but nothing about how much.

The original seal in my Whisper, beat and worn, measures .007 inch oversized.

In my new Bejamin Trail XL, the original seal, with very little wear, is about .020 over.

Paul.

[Bogey]

Excellent question.   How tight is too tight?   And how loose is too loose?    Is one situation better than the other?

[shady816]

i swear i read charlie's post in the gamo section stating 1 thousands over chamber bore but i could be mistaken.
check out this        http://www.gatewaytoairguns.com/airguns/forums/thread-view.asp?tid=25974&mid=205474#M205474

[Gene_SC]

That is what CDT wrote. Not a mistake. Use some good calipers. Sometimes because of the irregularity in the combustion tubes i have to re-size the seals. JM also makes oversize seals and undersize seals for oversize tubes and under size tubes for the home tuner.

[kiwi]

thanks guys...
i think a few of my guns maybe a wee bit on the tight side..

Pete

[airiscool]

That would explain why after about 1000 shots with the new seal in, my Whisper's velocity averages went up about 50-60 fps. The new seal had been about .011 oversized.

The Trail XL's new seal is about .015 over, but still .005 smaller than the factory seal. The velocity went up  a couple of FPS with just that .005 less oversize of the new seal.

Now I gotta figure out if I just keep shoot it and wait, or pull the piston and turn down the seal down on the lathe....  It's always something with this hobby !!!  :)

Paul.

[Gene_SC]

Paul there ae many things to learn about air guns..:) I learn something new every week.  One of them is you have to take into consideration that factory seals for the most part are nylon. The aftermarket poly seals are the best you can buy. You have to take into account that high production air guns will have some irregularities in the bore of the tubes. The poly seals for the most part will compensate.

[airiscool]

Gene.

I know what you mean.  I've learned alot on here and I feel like I've just scratched the surface.  I'm used to dealing with the tolerances involved in rebuilding antique machinery, air guns and their tolerances are a whole nuther animal !!!!

Paul.