S400 Breech seal still leaks

[Simonsays]

Following on from my earlier thread http://www.airgunbbs.com/showthread....urus-out-there, I have now got my new (to me) S400 up to scratch thanks to this forum (thanks again Chris, UKNeil et all). WIth the guidance it was a doddle.

Before stripping I noticed some blow back from the breech when firing so I replaced the breech seal.

Despite all being good in terms of performance, I am still getting the same amount of blow back through the new breech seal. Is this normal? If not, is there a tighter alternative or is it a new probe required?

As ever, I would appreciate words of wisdom.

[u.k.neil]

Pellet probe 'O' ring seal mate, inside the brass bush that the probe goes in to.

Neil

[oliver13]

Pellet probe 'O' ring seal mate, inside the brass bush that the probe goes in to.

Neil

What he said.
It's really a consumable & will wear eventually, but stuffing pellets in backwards or similar can knacker them pretty quick too.
Here's a handy S400 exploded diagram on Chamber's, I don't know if you've seen it, you want part no. OR056, https://www.gunspares.co.uk/shopdisp...=24238&Search=

If you can work out the size they will be a lot cheaper from a factors, & you might as well get a few spares as well.

[Simonsays]

Pellet probe 'O' ring seal mate, inside the brass bush that the probe goes in to.

Neil

Thanks Neil. Think I missed OR56. I have a seal set and wondered about this obe. It resides inside the bolt housing I assume?

I changed the seal OR 57 but I still feel the air escaping from around the probe tip in the breech.

[Simonsays]

What he said.
It's really a consumable & will wear eventually, but stuffing pellets in backwards or similar can knacker them pretty quick too.
Here's a handy S400 exploded diagram on Chamber's, I don't know if you've seen it, you want part no. OR056, https://www.gunspares.co.uk/shopdisp...=24238&Search=

If you can work out the size they will be a lot cheaper from a factors, & you might as well get a few spares as well.

Thanks very much Oliver, but I am confused here. OR57 is the internal barrel breech seal. Where does OR 56 reside please. Didnt spot it in the strip down. Note that I feel the air escaping from around the probe tip/loading port and hence I assume, OR56, not the bolt end. I have already changed this seal.

[u.k.neil]

Thanks very much Oliver, but I am confused here. OR57 is the internal barrel breech seal. Where does OR 56 reside please. Didnt spot it in the strip down. Note that I feel the air escaping from around the probe tip/loading port and hence I assume, OR56, not the bolt end. I have already changed this seal.

OR 056 is the one I am talking about mate. If it goes too bad it can actually lift the bolt.


Neil

[Simonsays]

OR 056 is the one I am talking about mate. If it goes too bad it can actually lift the bolt.


Neil

OK, gotcha. Thanks, I'll change this out when I get the new firing valve and main spring to go in.

[p.sharp]

Brother had a similar problem, it turned out the collet & seal were in back to front.

Probably very obvious, but worth checking all the same.

[martyn]

Check how straight the probe is to the bore, if it's not dead straight going into barrel the o ring it will always blow past. But the probe can easily be bent by hand as it's quite thin inside the housing.

[Simonsays]

Brother had a similar problem, it turned out the collet & seal were in back to front.

Probably very obvious, but worth checking all the same.

Thank you but er which collet and seal please?

[Simonsays]

Check how straight the probe is to the bore, if it's not dead straight going into barrel the o ring it will always blow past. But the probe can easily be bent by hand as it's quite thin inside the housing.

Cheers Martyn I'll check it out.

[bigm]

I change mine about every 1000 pellets. You can get packs of 10 x N70 seals from places like Sealforce in Dundee. Couple of quid posted. A bit tricky the first time but once you get the hang of it dead simple.
Hope this helps./Martin

[gb68]

Thanks very much Oliver, but I am confused here. OR57 is the internal barrel breech seal. Where does OR 56 reside please. Didnt spot it in the strip down. Note that I feel the air escaping from around the probe tip/loading port and hence I assume, OR56, not the bolt end. I have already changed this seal.

One is a .177 and t'other a .22 seal

[Simonsays]

I change mine about every 1000 pellets. You can get packs of 10 x N70 seals from places like Sealforce in Dundee. Couple of quid posted. A bit tricky the first time but once you get the hang of it dead simple.
Hope this helps./Martin

That's very helpful thanks bud. I'll order some up. I still need to resolve the blow by with the new seal I just fitted.

[Gwylan]

I've lost count of the number of shots I've put through my S400s. If you have to replace them every 2 tins, there's something wrong. OP, are you sure it's the breech seal? The transfer port Oring seal can leak from around the same area, and it's easily misplaced, or even lost, when you do a rebuild.

Gus