What material for new seal on CO2 pistol?

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ctshooter

ctshooter

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Oct 30, 2018
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CT, United States
I have a very old vintage CO2 pistol but it came without a seal for the CO2 cartridge piercing pin. I’m looking for some help on the right material to use to create a new seal.

I’ve had - use a Urathane rod - but I don’t know if the properties will resist the pressure of the CO2 and not stretch out without some other form of support.

I was thinking PTFE but I didn’t know if that was too hard to make a good seal. What if I machined a groove for an o-ring in the PTFE to support the o-ring from stretching?

Right now my solution is a seal from a Crosman 2240 CO2 valve which I am supporting from stretching with a metal washer carefully filed to just fit. It feel cludgy and requires me to remove the handles to line up everything just right when changing the CO2.
 
What you describe sounds like a good approach. It’s the same principle as a bonded seal washer (Dowty seal).
https://en.wikipedia.org/wiki/Bonded_seal

A simple (unsupported) O-ring on its own would not handle it. For example an -008 O-ring has an ID of 0.176” and assuming a slight squeeze applied to it to compress it from 0.070” to 0.060”, it has an internal area of about 0.033 sq in. An operating pressure of 850psi would therefore exert a force of ~28lbs attempting to expand the O-ring. So in other words just imagine pulling from the inside of a small O-ring with almost 30lbs of force, it’s going to stretch a lot. And of course as the O-ring expands, the pressure operates over a larger area and therefore exerts a growing force until the O-ring either ruptures or squirts out past the nose of the cartridge.

You might succeed with your other plan of machining a flat washer from polyurethane rod (90 or 95 durometer) if the ID can be made small and the OD somewhat large, however a rigid supporting ring would be the preferred way for sure.
 
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Yes - I found the o-ring by itself gets turned to deformed mush just by itself.
I think it will help better if I show a picture of what I am working with. I was emailing with Jimmie Dee about it and he had recommended the urethane tubing as an option.

Luger CO2 - 1.jpeg

Luger CO2 - 1 (1).jpeg
 
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