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Anyone else got any thoughts or knows someone who has done this conversion?
Or has any ideas for alternative cup washers or can help with an O ring that might fit?
I'm also still slightly suspect of the Breech washer, ones I've got from dealers don't seem that great - anyone got a supply of better ones or tubing that can be cut to fit?
Max; looking for: Baikal IZH 61 side lever rifle
Politically Incorrect
I've still got a few original Webley 'Nitrile' breech washers @ £3.80 posted to UK address.
They can be a pig to fit, but a touch of lubricant can help and they sometimes need fine trimming for the barrel to close properly.
Even the original tool used for the fitting of the leather and brass breech seals doesn't help much with the 'Nitrile' seals, but it's better than nothing.
Last edited by Troubledshooter; 06-03-2019 at 01:49 PM. Reason: wrong postage.
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Cheers David, I'll take a couple and PM you.
You got any other thoughts on the whole power/PB ring/conversion to cup etc? You know more about these pistols than most!
What I might do is find an older scrappy/bitsa MK I or Senior to break up and mod the piston from that to try.
Max; looking for: Baikal IZH 61 side lever rifle
Politically Incorrect
Originally Posted by felix gunner
Cheers David, I'll take a couple and PM you.
You got any other thoughts on the whole power/PB ring/conversion to cup etc? You know more about these pistols than most!
What I might do is find an older scrappy/bitsa MK I or Senior to break up and mod the piston from that to try.
There are others on the BBS who know a lot more about the workings of Webley air guns than I do, as I seldom strip them. I occasionally get the inclination to have a play if I come across a problem, but that inclination doesn't occur often nowadays as I'm winding down my collection.
I've never attempted a piston conversion such as you are considering, as I don't have the facilities to carry it out. This lack of power has been discussed previously on the BBS and I think you have covered all the main reasons for it.
The old leather and brass breech seals can be a problem if they've been allowed to dry out, as can a tired mainspring or worn piston ring, so the only thing to try after thoroughly cleaning the cylinder etc., is replacements for all, and if that doesn't improve matters much, I don't know what to suggest.
I've probably got a used Senior piston amongst my spares, so PM if you want one.
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I fitted a new rubber breech washer (from Knibbs I think), I had to trim about 1mm off it to get the barrel to latch, but it was a fantastic improvement in power over the leather and brass original which had dried out and started to crumble - no amount of oil would restore it!
My power measuring is based on bean-can bashing; when I first got it, 0.22 pellets would bounce off, but after the new seal, they would punch hole in the can, sometimes though both sides.
However, my 0.22 Tempest will easily punch through both sides, and is a darn-sight easier to cock. But I still love shooting my Senior!
Too many guns, or not enough time?
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Felix hi, I can understand your frustration with the piston ring system and if you want to tinker a little more, I have genuine original Webley piston ring material for sale. It does have to be pretty accurate to be fair, but with the 45 degree angled cut and care in fitting, air loss is fairly minimal and the gun was never considered under-powered for its era.
I do agree a piston seal of leather is probably better, but MKI leather piston washers aren't that easy to find. However I have successfully fitted a leather conversion to the senior in several guns. I actually had to resort to using Junior outer washers with an oversize custom made inner, made from nylon, this expands the outer washer enough to fit the senior cylinder. The pistons do seem to vary in hardness and I have had to resort to grinding the surface away a little to allow machining with carbon tip tools.
I measure the piston length overall, drill and tap the front [size can be to suit yourself, but I use M5 countersunk allen screws]; cut the front off and machine to the back face of the piston ring groove.
I build up the new inner and outer; then screw this unit to the piston tightly to expand the outer enough; then measure the length, determine the shortfall and make up a nylon backing washer. This actually simplifies things a bit and I have to accept you have enough engineering knowledge to attempt it. It does make for a nicer shooting pistol, but in general terms not that much more powerful than the average of the model. I fully understand the reasoning behind not wanting to modify an original piston, it's a big decision and I've only done it as a last resort after explaining to owners the risks and benefits and how difficult it can be to fit a new ring to factory standards, those guys were very talented for sure.
Hope this is useful and If I can be of any more help, please PM me for an e mail address.
abellringer
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Thanks very much for that info, fantastic - I now have a spare Senior piston and a selection of leather washers to try so I have some experimenting to do.
Before I go further though I will try this piston as it has it's original PB ring and see what that does.
I have contacts at an engineering firm but will they have issues then trying to mill down the end of the piston?
Max; looking for: Baikal IZH 61 side lever rifle
Registered User
Hi
I am very interested by this thread as I will have to refurb my junior. Junior has a leather piston seal but the breech seal is my main concern.
For my curiosity, I have a few questions for you guys:
What does 'PB ring' stands for?
What is the material of this ring?
Beryllium copper?
Many thanks
I Like Gingers Best
PB stands for phosphor bronze.
blah blah
Even a stopped clock is right twice a day
'Phosphor Bronze', answers both questions I think
I must admit to always being very keen on the concept of the PB piston seal. As I understand it the reason it was not used in future Webleys was due to cost, rather than leather seals being an improvement.
IIRC the FWB65 uses a PB piston ring, and that was not a 'cheap', or half-arsed, pistol.
They are meant to have an extremely long shelf life, I seem to recall figures like a half million, or a million shot cycles bandied about, particularly with reference to the FWB65. For that reason I'd be inclined to keep it in situ...
Good deals with these members
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Agree with that 100%.'Phosphor Bronze', answers both questions I think
I must admit to always being very keen on the concept of the PB piston seal. As I understand it the reason it was not used in future Webleys was due to cost, rather than leather seals being an improvement.
IIRC the FWB65 uses a PB piston ring, and that was not a 'cheap', or half-arsed, pistol.
They are meant to have an extremely long shelf life, I seem to recall figures like a half million, or a million shot cycles bandied about, particularly with reference to the FWB65. For that reason I'd be inclined to keep it in situ...
The FWB 300 rifle uses a split ring as well, though I am sure steel ones with a stepped split section (higher performing) are advertised as non original replacements.
I think there is absolutely nothing that a half decent split ring cannot handle in airgun cylinder pressures since they have been used for ages in high compression turbo-charged diesel engines and last many years in the harshest compression cycle one can imagine.
I think a reasonably competent person with a lathe can turn a few rings effortlessly if the cylinder bore is still true and the piston groove/cylinder dimensions are known. I would hate to loose more of what little power these fine pistols make by fitting leather washers.
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