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PostPosted: Tue May 09, 2017 10:32 am 
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Joined: Tue Feb 18, 2014 3:10 pm
Posts: 175
I just resealed five cylinders for my early Steyr CO2 pistol (CO2 Match, LP-1p, LP-1) with the following SAE (US Spec) polyurethane o-rings...

#020 - Tube to valve assembly seal
#005 - Internal valve stem seal

Polyurethane (cream or green color, doesn't matter) is recommended for longevity as they won't absorb CO2 gas, particularly the 005 o-ring that soaks in the liquid CO2. You can use a BUNA-90, 020 o-ring, or the factory 2mm x 20mm for the larger seal. But you will need to replace it more often.

Mine cylinders are now good for another 25 years. Have fun with yours...


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PostPosted: Tue May 09, 2017 10:52 am 
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Joined: Sat Sep 04, 2004 6:04 pm
Posts: 1346
Location: Massachusetts
Good to know. Thanks!

Did you get the polyurethane O-rings from McMaster Carr? I see that they carry those sizes.

Also, did you get the durometer 90 rings, or just 70? 70 may be OK for CO2, but PCP would probably be better off with 90.


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PostPosted: Tue May 09, 2017 11:07 am 
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Joined: Tue Feb 18, 2014 3:10 pm
Posts: 175
Gwhite wrote:
Good to know. Thanks!

Did you get the polyurethane O-rings from McMaster Carr? I see that they carry those sizes.

Also, did you get the durometer 90 rings, or just 70? 70 may be OK for CO2, but PCP would probably be better off with 90.


McMaster Carr carries these for quantity purchase, but I bought just the number I needed locally here in Dallas. These are quite expensive o-rings.

Duro 70 will probably be best for CO2, especially for the 020, as it will seat more easily (staticlly-mounted) against the tube. But I bought the 90's and they work fine.


Last edited by DFWdude on Tue May 09, 2017 12:04 pm, edited 1 time in total.

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PostPosted: Tue May 09, 2017 11:13 am 
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Joined: Tue Feb 18, 2014 3:10 pm
Posts: 175
BTW, the 005 o-rings will fit over the valve stem loosely. Don't be upset to see this, because this is what you want. Remove the old seal and you will see it falls off, too. The Steyr design is simple, and efficient, with the valve stem simply capturing the o-ring between the metal sealing surfaces. The loose o-ring permits the CO2 to exit once the seal is cracked. And you can just imagine the o-ring floating back and forth on the stem within the liquid CO2 once on the gun.

You can try a smaller ID o-ring, but it will seal against the stem shaft, and prove impossible to crack the seal open, either with the bleeder tool, or when mounted on the pistol. Trust me on this as I tried it. All I got was a full cylinder of CO2 and no way to drain it. And I'm not about to describe how I did it, either.


Last edited by DFWdude on Tue May 09, 2017 4:19 pm, edited 2 times in total.

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PostPosted: Tue May 09, 2017 11:18 am 
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Joined: Thu May 22, 2008 2:21 pm
Posts: 23
Location: Virginia
If they are static o-rings, 70 durometer is likely good enough. The o-ring store sells 70 and 90 durometer polyurethane o-rings in cast or polyether urethane (EU): http://www.theoringstore.com/index.php? ... &cPath=367

I've found that if an order is already in place for McMaster-Carr, larger quantities can be added for similar o-rings at about the same price. The o-ring store used to ship for less, but I think they realized that business model was not sustainable.


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