Loose part in pressure vessel

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Ralph Fairbrother
Posts: 1
Joined: Mon Sep 10, 2018 8:58 am

Loose part in pressure vessel

Mon Sep 10, 2018 9:09 am

I am new to the forum so please excuse if this has been answered before.
My 14 month old S400f carbine has a loose part inside the pressure vessel that can be heard rolling from one end to the other when the gun is tipped each way. The gun still works but obviously I won't use it in this condition. Any advice would be appreciated. Thanks

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Posts: 9
Joined: Sat Jul 21, 2018 10:29 am

Re: Loose part in pressure vessel

Mon Sep 10, 2018 12:32 pm

Although your rifle is out of warranty, I'd be inclined to take it to the supplier and try to persuade him to cover it - try citing the new extended warranty, maybe? Unless you are comfortable working on the high pressure side of the gun it will be safer to get a gunsmith to sort it for you.

The part that seems most likely to be able to come loose and roll around in the cylinder is part of the pot. This is a brass cylinder which controls the feed of air to the firing valve. It fits onto the firing valve spring holder and the two are considered as one part. It should be an interference fit onto the spring holder and I believe is also held by some Loctite.

In actual fact, if the fault is as I suspect, then it could be rectified without having to breach the Anti Tamper devices. All the air must be allowed to escape (usually by dry firing) and then the fill valve body can be cracked open a tad to ensure the process is complete. Take your time in depressurising it. Remove the barrel support and the air cylinder can be unscrewed. If a small brass cylinder drops out, then it can be Loctited back onto the brass spring holder body and the whole thing reassembled. Some caution is required to ensure that the o-rings are undamaged. They should be re-greased before assembly - just a wipe of silicon grease.

Re-charging the cylinder requires the rifle to be cocked and the bolt close, otherwise air will simply flow past the firing valve and escape down the barrel. It takes a cylinder pressure of around 50 bar before this stops. Check all the joints for leaks .


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Joined: Mon May 29, 2017 10:55 am

Re: Loose part in pressure vessel

Mon Sep 10, 2018 11:40 pm

Yes, almost certainly the pot has come loose... happened to mine... not enough Loctite. Take care when reassembling to glue it back in the correct position. If the original position is not obvious you can set it at 57mm overall length with valve body screwed in. I'd suggest you don't move the remaining section (valve body) until the tube is glued back in place otherwise you loose the datum for your measurement, although I expect Air Arms could advise correct overall length with valve body out.

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