S400 service, what's needed ?

[trumpetier]

Just bought my old S400 back a few days ago. It's a 2006 model. I believe the firing valves need replacing on these every so often, my question is what should I get to give it a good service, seals, springs, firing valve etc ? I previously owned it for a couple of years without it needing anything, it holds air fine, but feel it's probably well overdue a good service.

[Stoohundred]

Contact Julian on here (bgaltd). Or google air arms spares / bond gun accessories.

You need s701 seal kit which is all the O-ring that will need replacing.

I would also replace the main Spring s331
The firing valve Spring s306
And the valve stem itself, s370 (Most important for good performance)

I have just bought all the same parts myself for a full service on my MPR and the total £ was £21.23 including postage

If the filler end of the cylinder is all fine and has no leaks then there isn't really any need to change those seals unless you realy want to (if it ain't broke don't fix it) then you can keep the new ones as spares should it develop a leak, but then again replacing these seals could prevent a future leak, (prevention is better than cure) the choice it yours.

All the other seals are best replaced as they would effect the performance and or safety of the rifle.

The breach/barrel seal can be replaced without removing the barrel if you use a fine set of tweezers or a blunt pin, but it's best to remove the barrel and change it to avoid damaging it and get a good seal

There is a fairly small o-ring that sits between the transfer ports on the firing valve and the barrel block which is easy to loose when taking it apart and also very fiddly to place it correctly when re-assembling so look out and take care of that one.

Also whilst you have it apart, de-grease and polish the hammer rail and the inside of the hammer that slides along the rail and just put a very small amount of light oil (3 in one) on it when you put it back together. This will improve the consistency of the rifle.

Also BEFORE you remove the firing pot (the brass pot inside the cylinder) make sure you measure it to see how far it's screwed in so you can reset it back the same after replacing the valve Spring. Although I think they are set to about 57.5mm in the factory. This is essential to get the correct performance and consistency from your rifle. And note that there is a little grub screw (underneath the gauge block) that needs to be loosened before you can unscrew the firing pot.

After all this it will be essential to chrono the rifle to check the power is legal and adjust it down with the Transfer port screw if needed, as replacing some of these springs may well put the rifle over the 12ft lb limmit.

Cheers , Sean

[Geordie]

+1 for the above.
Nothing more to add other than to say I run my hammer/hammer rail dry (no oil)

[trumpetier]

Many thanks guys for the very informative replies.