S400 Pressure Gauge O ring Sizes

[lensman57]

Can someone please tell me the exact sizes of the S400 Pressure gauge O rings ? One is stated as S536 and another as S427 . I need to know their exact sizes for a late S400 ( 2014 model ) . Mine seems to have disintegrated for some reason and is not measurable.

Many thanks,

A.G

[UrbanFox]

I have the S536 as 4.5 x 1.5 NBR 70 which is also the .177 barrel seal.
S427 at 6 x 1 same as TP seal but I find the TP seal is better at 6 x 1.5 which stops blow out on some rifles.

Hope that helps.

Bri

[bezzer]

I have the S536 as 4.5 x 1.5 NBR 70 which is also the .177 barrel seal.
S427 at 6 x 1 same as TP seal but I find the TP seal is better at 6 x 1.5 which stops blow out on some rifles.

Hope that helps.

Bri

Spot on, but I've never had a problem with the 6X1

[Archer50]

I find the TP seal is better at 6 x 1.5 which stops blow out on some rifles. Bri

Definitely - good on my S400, almost essential on my HFT 500.

Alan

[lensman57]

Thank you gentlemen for your assistance. May I ask if the one that seals the body of the pressure gauge to the action is S 427 or the other way around please?

A.G

[UrbanFox]

S427 seals the Gauge mount to the Firing Valve body and is also used to seal the Transfer Port to the bolt housing. As said above some seals that are 6 x 1 and used on the TP will blow out and you think you forgot to replace it on reassembly!!! My 400 needs the 6 x 1.5 seal RN 219 -9 seals the guage to the Gauge mount.
Heres a pdf file for the parts but doesn't give sizes.
https://www.milidonis.gr/images/part...-arms-iss2.pdf

Bri

[ChrisC]

S427 seals the Gauge mount to the Firing Valve body and is also used to seal the Transfer Port to the bolt housing. As said above some seals that are 6 x 1 and used on the TP will blow out and you think you forgot to replace it on reassembly!!! My 400 needs the 6 x 1.5 seal RN 219 -9 seals the guage to the Gauge mount.
Heres a pdf file for the parts but doesn't give sizes.
https://www.milidonis.gr/images/part...-arms-iss2.pdf

Bri

Good advice with the 6x1.5.... along time ago UKneil made me some brass shims that sat in the TP recess to stop the blowout.

[lensman57]

Well, I have changed both the 536 and 427, twice and still no luck. It is still leaking. Now it is highly unlikely it would leak from the cylinder and fill O rings so I have to examine the firing valve itself. To top it up the cylinder is stock to the firing block and no amount of torquing is able to rlease it. I will try to heat the end with a hair dryer and use a rubber grip to see if I could get the damned cylinder off.
I can't think of any other place the gun could leak from so any advice is most welcome.

Thanks and Regards,

A.G

[bezzer]

If the leak isn't obvious you need to narrow it down instead of chasing your tail, guessing and replacing what it might be. It won't hurt to use a bucket or bowl of water, stick the action in it to confirm or discount where it's coming then just make sure you dry it off properly afterwards. Never had a problem at the firing block end of the air cylinder it's always been the filling end for me, bit of hairdryer heat and the rubber strap does seems the best way to go, padded vice is always the last resort.

[lensman57]

If the leak isn't obvious you need to narrow it down instead of chasing your tail, guessing and replacing what it might be. It won't hurt to use a bucket or bowl of water, stick the action in it to confirm or discount where it's coming then just make sure you dry it off properly afterwards. Never had a problem at the firing block end of the air cylinder it's always been the filling end for me, bit of hairdryer heat and the rubber strap does seems the best way to go, padded vice is always the last resort.

I have thought of the bucket. Might spray the gun with gun oil and then put it in water. I can clean the bits later as the AT has been removed.

A.G

[Rich]

I'd have a look at the filler valve. I got fed up with the old nozzle type failing and bought a replacement kit comprising a new end plug and the barrel type filler with the two O rings, and a new dust cap.

Fitted that, stood back and admired how smart it looked, filled the rifle and overnight it was empty.

Took the new filler out and had a look at the small internal O ring to find it was compressed out of circular in section, and as hard and unforgiving as shoe leather. Popped a new one on and it's been fine ever since. That was about six months ago.

I guess the filler must have been old stock.