QB 79 valve O-Ring

QB 79 valve O-Ring

Joined: February 18th, 2012, 3:01 pm

April 20th, 2012, 3:40 am #1

Picked up one of my all times wants in Findlay on Saturday, thanks to Ted Summers... A .177 QB 79 with a 3.5oz tank. After finding a safety and getting the tank filled I was ready to see if she held air...she didn't. I had to replace o-rings with what BUNA o-rings I had and could get at the hardware store.(Also found out a crosman 2100 breach seal works for the QB's in a pinch)

My question is about using a BUNA #113 for the valve how long will the o-ring probably last? I plan to mainly use a 20oz. CO2 tank with a remote, which I think if I keep the tank vertical, it will keep liquid CO2 from getting inside the rifle, which in paintball is the major cause of o-ring failure....I guess I really tossing the idea out there to see if BUNA is probably ok if it is not going to be in contact with liquid CO2 much.

I plan to upgrade to the xp valve/bolt in the next few years, but don't want to be tearing the rifle apart alot until then or ordering excess amounts of valve o-rings.
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Joined: December 5th, 2008, 8:43 pm

April 20th, 2012, 7:45 am #2

The valve o-ring does come in contact with co2, but if you coat it with silicone grease it should make a good seal and last a good while ,
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Joined: January 9th, 2005, 1:46 am

April 20th, 2012, 1:04 pm #3

Picked up one of my all times wants in Findlay on Saturday, thanks to Ted Summers... A .177 QB 79 with a 3.5oz tank. After finding a safety and getting the tank filled I was ready to see if she held air...she didn't. I had to replace o-rings with what BUNA o-rings I had and could get at the hardware store.(Also found out a crosman 2100 breach seal works for the QB's in a pinch)

My question is about using a BUNA #113 for the valve how long will the o-ring probably last? I plan to mainly use a 20oz. CO2 tank with a remote, which I think if I keep the tank vertical, it will keep liquid CO2 from getting inside the rifle, which in paintball is the major cause of o-ring failure....I guess I really tossing the idea out there to see if BUNA is probably ok if it is not going to be in contact with liquid CO2 much.

I plan to upgrade to the xp valve/bolt in the next few years, but don't want to be tearing the rifle apart alot until then or ordering excess amounts of valve o-rings.
Derek, I hope you will enjoy your new QB79!

In my experience, Buna works well for the barrel O rings (where CO2 exposure is intermittent and brief). We've found that EPDM and Urethane rings are superior for the valve O ring, however.

The factory has used a variety of O rings styles for the valve and tank block. The material for both O rings has normally been urethane in recent years.

But I have found that the factory O rings around the tank block tend to split apart at their join after some years and BUNA can work well there as the material is more flexible. Factory O rings in this position can be green, purple or cream-colored - the cream Urethane rings are generally seen on more recent examples.

I'm sure others will also chime-in with their experience, too

Stephen Archer
Archer Airguns Inc.
Online stores http://www.archerairguns.com
http://www.archerpelletguns.com
Videos http://www.youtube.com/ArcherAirguns
Blog http://www.archerairguns.info
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Joined: January 14th, 2011, 9:42 pm

April 20th, 2012, 1:42 pm #4

Picked up one of my all times wants in Findlay on Saturday, thanks to Ted Summers... A .177 QB 79 with a 3.5oz tank. After finding a safety and getting the tank filled I was ready to see if she held air...she didn't. I had to replace o-rings with what BUNA o-rings I had and could get at the hardware store.(Also found out a crosman 2100 breach seal works for the QB's in a pinch)

My question is about using a BUNA #113 for the valve how long will the o-ring probably last? I plan to mainly use a 20oz. CO2 tank with a remote, which I think if I keep the tank vertical, it will keep liquid CO2 from getting inside the rifle, which in paintball is the major cause of o-ring failure....I guess I really tossing the idea out there to see if BUNA is probably ok if it is not going to be in contact with liquid CO2 much.

I plan to upgrade to the xp valve/bolt in the next few years, but don't want to be tearing the rifle apart alot until then or ordering excess amounts of valve o-rings.
... I put a very small chamfer on the joint where the valve body meets - top piece only. Then used a urethane o-ring from a paintball tank that you can get on ebay for $8 for 100 and reinstalled.

The chamfer helped the o-ring fit to the tube and it hasn't leaked since. It was converted to a regulated HPA bottle running at 1100PSI 2 years ago and it still doesn't leak.
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Joined: September 21st, 2007, 12:13 pm

April 20th, 2012, 2:40 pm #5

Picked up one of my all times wants in Findlay on Saturday, thanks to Ted Summers... A .177 QB 79 with a 3.5oz tank. After finding a safety and getting the tank filled I was ready to see if she held air...she didn't. I had to replace o-rings with what BUNA o-rings I had and could get at the hardware store.(Also found out a crosman 2100 breach seal works for the QB's in a pinch)

My question is about using a BUNA #113 for the valve how long will the o-ring probably last? I plan to mainly use a 20oz. CO2 tank with a remote, which I think if I keep the tank vertical, it will keep liquid CO2 from getting inside the rifle, which in paintball is the major cause of o-ring failure....I guess I really tossing the idea out there to see if BUNA is probably ok if it is not going to be in contact with liquid CO2 much.

I plan to upgrade to the xp valve/bolt in the next few years, but don't want to be tearing the rifle apart alot until then or ordering excess amounts of valve o-rings.
the major o ring suppliers their first choice of o ring material for co2 both gas and liquid is Buna (nitrile).
The problem is most hardware stores etc. carry Chinese assorted o rings, which are junk. I've found that U.S made Mil Spec Buna is the best for co2 and it doesn't saturate, and lasts for years.
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Joined: February 16th, 2007, 5:58 am

April 20th, 2012, 4:41 pm #6

I believe the O-rings my dad got me years ago (pre-2000...) were EPDM, for a paintball tank. He used them at work to test with CO2, and I never had an issue with them...

Urethane are probably best, if you can get them in small quantities.
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Joined: February 18th, 2012, 3:01 pm

April 21st, 2012, 5:44 am #7

Picked up one of my all times wants in Findlay on Saturday, thanks to Ted Summers... A .177 QB 79 with a 3.5oz tank. After finding a safety and getting the tank filled I was ready to see if she held air...she didn't. I had to replace o-rings with what BUNA o-rings I had and could get at the hardware store.(Also found out a crosman 2100 breach seal works for the QB's in a pinch)

My question is about using a BUNA #113 for the valve how long will the o-ring probably last? I plan to mainly use a 20oz. CO2 tank with a remote, which I think if I keep the tank vertical, it will keep liquid CO2 from getting inside the rifle, which in paintball is the major cause of o-ring failure....I guess I really tossing the idea out there to see if BUNA is probably ok if it is not going to be in contact with liquid CO2 much.

I plan to upgrade to the xp valve/bolt in the next few years, but don't want to be tearing the rifle apart alot until then or ordering excess amounts of valve o-rings.
Decided to Order some EPDM and other BUNA o-rings from the oringstore.com, will see how long hardware orings last and I will have replacements on hand then so I wont have much down time when it happens.
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