Degassed and dissap...
 

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El pelletas
(@el-pelletas)
Joined: 2 years ago
Posts: 116
2018-09-19 18:27:59  

So, last Saturday me and a couple of my kids drove to their grandpa's house with the intention of shooting some guns that don't see much action, namely a crosman phantom, crosman Titan gp and a qb 79 in. 22cal..we got there and set up some targets at around 25 yards, lubed and installed a 90 grams co2 cylinder on the qb 79 but, as soon as I was done tightening the cylinder, it started to leak the c02 under the breech, to mine and my kids surprise, a couple of months ago I shot it and it seemed fine.. Need less to say it went right back to the gun bag and we just shot the springers. .My question is.. What size o rings do I need to change all of them once I get to work on it?  I have done some searching but I don't see anything conclusive ... Thank you guys for reading.. 

Land and Liberty.......


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ribbonstone
(@ribbonstone)
Joined: 2 years ago
Posts: 238
2018-09-19 18:45:42  

Everything that relies on 0-rings to seal will sooner or later unseal.

 

 

Airguns, co2 or PCP, rely on basic cheap O-rings to keep the gas in,

 

So $1500 PCP or $100 co2, it'sthe O-rings that seal the rifle...and they are like brake pads/car tiers/ A/C furnace air fileters/ springer pistol seals? or  water facet washers....sooner or later, they give up and can't do their job.

 

 

Which is pretty much why "they" used replaceable seals to begin with.

 


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ray1377
(@ray1377)
Joined: 2 years ago
Posts: 22
2018-09-19 21:20:40  

The O-ring sizes for QB79 / QB78 rifles are:

1. Valve -113
2. Barrel -012 [qty 3]
3. .177 bolt -003
4. .22 bolt -006

 

Thanks

Ray


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Bob in WV
(@bob-in-wv)
Joined: 2 years ago
Posts: 126
2018-09-19 22:30:40  

A good reseal should replace the exhaust valve too.

 

Bob in WV


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marflow
(@marflow)
Joined: 2 years ago
Posts: 631
2018-09-19 22:53:12  

make the O-rings urethane or polyurethane if they touch co2 and if I was you I would get the adapter that uses 2-12gr carts, dumping a 88-90 gr cartridge is no fun at all

I have 2 hammerli 850's and made up some single 12gr setups for testing and short shooting sessions, you can find them on Ebay for 12-13 bucks or less, I add some tubing so they were the same length as a 88gr tank but in your case that would not be needed

so you only get 30 shots??? but there will be no wasting  a 88gr tank if something is amiss

https://www.airgundepot.com/850-adapter.html

https://www.krale-schietsport.nl/en/co2-adaptor-walther-2x12-gram-8558.html

https://www.ebay.com/itm/1-2PCS-12g-Quick-Change-Gram-CO2-Cartridge-Adapter-Black-With-88g-Bottle-Threads/372281452954?hash=item56adb4299a%3Am%3AmvDQ7J5Mm9GsYLHM7Ah8JFw&var=641115093160

 

just ideas and the O-ring store should have anything you need

 

https://www.theoringstore.com/

good luck and take care

mike

 

 

Mike


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El pelletas
(@el-pelletas)
Joined: 2 years ago
Posts: 116
2018-09-19 23:20:44  

Thanks a lot guys.. You are very helpful and kind. I appreciate the time and effort you put into your posts.. It's great to be part of this forum.. 

Land and Liberty.......


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Voltar1
(@voltar1)
Joined: 1 year ago
Posts: 2
2018-09-20 11:39:11  

QB valve bodies mustbe tight to seal the oring to tube. Yours might be loose. Check that first


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nervoustrigger
(@nervoustrigger)
Joined: 2 years ago
Posts: 184
2018-09-20 15:41:34  

Actually the valve body does not have to be squeezed tight to the O-ring.  The application of pressure pushes the O-ring to the shoulder near the atmosphere side and seals off against the extrusion gap.  All the valve has to do is keep the O-ring from falling off as you slide it down the tube and into place.

Granted it certainly won’t hurt to tighten it but it is not required. 


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ribbonstone
(@ribbonstone)
Joined: 2 years ago
Posts: 238
2018-09-20 16:32:14  

So far, it'sworked out better over all for a rifle a few years old to get a full reseal. A nearly new rifle with a leak problem, I might just hunt doen the leak and fix that one thing....but not on one that's got a few years on it.

Riflewas assmelbed at once, so all the o-rings can't be any newer than when it was put together. O-rings could be older as they are just parts on hand at the factory, so could be a bit older than the assembly date.

So when one dies, the others may still seal well....but why bet on old-o-rings? It would like be replacing the water pump on your car, but deciding to use the old gaskets and hoses.


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El pelletas
(@el-pelletas)
Joined: 2 years ago
Posts: 116
2018-09-24 19:31:42  

Gentlemen,has any of you ordered a reseal kit from e bay or any online retailer specifically for this gun?or can this o rings be  bought at home Depot? O ring stores are confusing, to me at least ... Thank you guys for your help .. ..

Land and Liberty.......


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marflow
(@marflow)
Joined: 2 years ago
Posts: 631
2018-09-24 23:54:50  

if you know the size of the o-ring and it touches co2 it should be urethane, if you use a different material it will work but will fail, most other materials will absorb the co2 and swell

when buying o-rings and you are not sure of the hardness buy several in different hardness

70 duro or 90 duro

sometimes an o-ring that needs to be metric can be swapped out with a inch one but you have to know the size, up in the post some states a 113 as the valve size o-ring and there is no metric at the Oring store in urethane that will cross over so if that is your size, the 113 are found in the 100 series urethane section  they come in both 70 and 90 duroand the 113 is a 2.381 mm cross section with a 14.288 mm inside diameter

that all I have

mike

Mike


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