Webley Mk3 (serial 9350) - Piston Washer Advice

[deejayuu]

Chieftool. Well done A+ for persevering. If you strip piston out again try making a thin plastic/metal sleeve to get the seal back without damage.
I've used old photo negative, pop bottle, beer can just like a spring sleeve really. Slight funnel through thread area first then offer the piston up.

[chieffool]

Chieftool. Well done A+ for persevering. If you strip piston out again try making a thin plastic/metal sleeve to get the seal back without damage.
I've used old photo negative, pop bottle, beer can just like a spring sleeve really. Slight funnel through thread area first then offer the piston up.

neat idea. The harder (AR20) washer was 'fiddly to fit' back in - 'gentle persuasion' needed to squeeze it past the problem areas that might damage it.


I also tried an alternative SOFTER (Protek) Washer:

I'll load up some pics so that others can see the difference between the two options (hard vs soft).
This 'soft' washer was an alternative suggested to try (and obviously this is just my opinion and experience) BUT...
...No shaping required.... ...
...No soaking needed.... (you use a silicone gun oil)
...and (oh yes) - No f@kkin good!!

[AC99]

I don't think I can further add to mk3 washer suggestions which now seems quite extensive and far reaching but I carried out muzzle velocity (chronograph) tests on my first and second mk3's bought in 1959/60 when I was a youngster. One of these was a second-hand one (ribbed stock, about 1949 vintage) which I fitted with a new spring and washer supplied by Webley and still in situ. The second was bought new by my then neighbour's eldest son who sold it to me six months later when he he needed the cash to get engaged and it still has the original Webley factory-fitted spring and washer.
The average muzzle velocity of the first was 569fps and the second one achieved 573fps averaged over ten shots each.
An indispensable source of information for air-gun enthusiasts is "The Airgun from Trigger to Target" by Cardew last published in 1995 I think and which describes in some detail exhaustive tests on airguns changing several variables with some astonishing results. Chapter 3 gives detailed analysis on spring dimensions, methods of manufacture, heat treatment etc.
Hope this helps.

[chieffool]

many thanks. everything helps. Having the info to hand (to compare, etc) means the difference between recognising there is a problem (and tracking down to eliminate likely causes) to finally finding a solution.

[chieffool]

neat idea. The harder (AR20) washer was 'fiddly to fit' back in - 'gentle persuasion' needed to squeeze it past the problem areas that might damage it.


I also tried an alternative SOFTER (Protek) Washer:

I'll load up some pics so that others can see the difference between the two options (hard vs soft).
This 'soft' washer was an alternative suggested to try (and obviously this is just my opinion and experience) BUT...
...No shaping required.... ...
...No soaking needed.... (you use a silicone gun oil)
...and (oh yes) - No f@kkin good!!

some pics: self-explanatory i believe. My 'hard washer' as you can see (having resoaked and refitted as described above) is now a very good seal. Haven't bothered with describing the process off/on, resoaking, prep, etc as covered in previous. So bear in mind that the whole 'test' process took days of soaking, allowing to set inside the gun, etc - and then i've put together this series of pics FYI:


http://s296.photobucket.com/user/chi...7xhi3.jpg.html
Knibbs 'hard washer' AR20

http://s296.photobucket.com/user/chi...dowis.jpg.html
AR20 fitted and Protek 'soft' washer waiting

http://s296.photobucket.com/user/chi...eurct.jpg.html
AR20 off and Protek soft washer on

http://s296.photobucket.com/user/chi...h88g9.jpg.html
Soft washer AFTER about 30+ pellets. Chrono results inconclusive as so erratic, but although compression seemed good, i just didn't have the confidence to keep it in the gun for any longer. When i took the piston out - the soft washer looked like it was ready to fall to pieces. It would (i'm sure) have lasted longer, but it was shedding bits of leather from the edge .... and that just can't be 'effective'.

SO:
The hard washer was refitted again - see my notes above on 're-spreading' the inner central hard leather disk to squeeze out the dry-shaped outer cup washer to improve fit/compression. Getting it back in was a fiddly (as tighter fit), but worth it. Compression is very good indeed.

[chieffool]

and just for completeness and clarity:

The Knibbs seal i fitted (and am happy with) is part no. AR20.
This is a complete kit: outer leather cup, inner leather flat washer, concave metal washer, machine screw head.
This requires shaping of the outer leather 'cup' very carefully when dry (ie turn the whole kit in a drill so that the screw shaft and washer hold the washer set straight and flat in the jig, and use sand paper to shape perfect washer. Keep checking fit). After shaping the dry washer, the leather then requires soaking (at least 12 hrs).... then careful fitting back.... leave to rest (again overnight) with gun uncocked.
http://www.airgunspares.com/store/pr...Part-No.-AR20/

The aim of this comparison was to try a different type of seal.

SO:
The Protek seal i tried (after discussing with one of their 'technicians') is part no. MPH3.
NOTE: This is NOT part no. W121 which is a 'hard' seal similar (identical for all i know?) to Knibbs part no. AR20.
This is softer, and is fitted in a completely different way.
No extensive pre-soaking. Fit straight to the end of the piston and liberally lubricate with a silicone Gun Oil.
Take time to carefully/gently fit the whole thing back into the air tube.
Leave at rest (i left overnight with gun uncocked in case it helps fit the seal to the air chamber).
http://www.proteksupplies.co.uk/piston-seals-etc.html



FINALLY: In my opinion the 'harder' seal from Knibbs (part AR20) is undoubtedly better for my gun when compared to the Protek 'softer' seal (part MPH3). Maybe someone has tried successfully the softer seal and swears by that instead...? or fitted the Protek 'hard seal' and thinks it better than the Knibbs? My end result suits me fine.

Equally importantly (although there are other parts suppliers out there) the people i spoke to from both companies were helpful, and happy to take the time to chat through the different stages required to fit both. Neither involves 'rocket science' but to get the best, you need to know the tweaks. Thanks Guys

PICS of both types in my post above

[abellringer]

I have a question regarding the piston in your photographs. It appears to be a machined one piece piston, which as I understand were the latest variant made, the guns serial number makes it a fairly early one, but these guns would have had a sheet steel / weld construction for the piston. These earlier pistons were prone to wear from the contact of the cocking arm to the rear of the slot in the piston, had that happened or has it been serviced to the extent that a replacement piston was fitted ?. I suppose there is little consequence to the answer, just that this seems "odd" in the normal context of the guns history.

Regards abellringer

[chieffool]

I have a question regarding the piston in your photographs. It appears to be a machined one piece piston, which as I understand were the latest variant made, the guns serial number makes it a fairly early one, but these guns would have had a sheet steel / weld construction for the piston. These earlier pistons were prone to wear from the contact of the cocking arm to the rear of the slot in the piston, had that happened or has it been serviced to the extent that a replacement piston was fitted ?. I suppose there is little consequence to the answer, just that this seems "odd" in the normal context of the guns history.

Regards abellringer

you definitely know more about it than i do. The serial (underside of cocking arm) is 9350, as is the number stamped into the wood of the gun visible when stock removed. Don't know of anyone ever doing anything to this before (and guns were a BIG thing in my family and always a constant discussion point). If anyone had - it would have been either Dad - or my elder brother (and sadly neither around to ask). Out of interest - what year would the number indicate?

[deejayuu]

13389 is featured in Thrale's book as circa '52. So my best guess is 1950 ish.

[chieffool]

13389 is featured in Thrale's book as circa '52. So my best guess is 1950 ish.

Thank you. Much appreciated.

[cliveyt]

Weirder than that: the old spring i took out (29 coils) only measures 220mm, and produces on my combro crono 434-438 fps, @6.3/6.7 ft lbs. This was the reason i decided on replacing it.


You need to be using a true 5.6mm pellet to get the best out of a mark iii

[chieffool]

Weirder than that: the old spring i took out (29 coils) only measures 220mm, and produces on my combro crono 434-438 fps, @6.3/6.7 ft lbs. This was the reason i decided on replacing it.


You need to be using a true 5.6mm pellet to get the best out of a mark iii

in the 1960s we used to shoot any old thing. I'm using WASP no.2 /5.6mm now - not many 5.6 options about, but better than a 5.5 obviously.

Will post up results when my new 'Webley new/old' spring arrives courtesy of a very generous soul in New Zealand! Winging its way for next week i believe. Extraordinary that a forum such as this can produce such good and helpful people and am eternally grateful.

....and the new washer (ref all the stuff above and reason for the thread) has really good compression now (actually improved over last week of 'resting' - so high hopes for the spring!

[abellringer]

Hi from abellringer again; I have done some checking around and it seems I was correct regarding the production of W & S MKIII pistons; the earlier ones were fabricated from sheet steel and the latter ones from solid, however no one seems to have a specific date for the change. I know from experience in the mid 70's I personally was changing fabricated pistons to machined ones; again as I said it is something of an irrelevance with regards to any particular gun, just that it triggered something in my mind as out of the ordinary. It will be nice to hear your report of when the gun is up and running again as that is always my intention with any gun I work on, I like to think I can "with safety and integrity keep as many guns working as possible for as long as possible". Nice to see also, how many people have contributed to the thread with so much info.
abellringer

[chieffool]

i really do appreciate all the comments. I'm not the only one facing similar problems, or the first to deal with things like this as a novice - but already i feel as though i've gained enough collective experience to get the best out a (treasured) gun, and ensure its continued existence.

I'll be summarising all the chrono results as soon as i get the new spring in and fitted. Have advice on preload, and any suggested coil-cutting to tailor the spring.... high hopes!

[isobar]

in the 1960s we used to shoot any old thing. I'm using WASP no.2 /5.6mm now - not many 5.6 options about, but better than a 5.5 obviously.

Will post up results when my new 'Webley new/old' spring arrives courtesy of a very generous soul in New Zealand! Winging its way for next week i believe. Extraordinary that a forum such as this can produce such good and helpful people and am eternally grateful.

....and the new washer (ref all the stuff above and reason for the thread) has really good compression now (actually improved over last week of 'resting' - so high hopes for the spring!

as regards to pellets,i have been using milbro select in my mk3.they are stated as 5.5 but are a tad bigger as they won't fit my german 5.5 barrel.i am getting very good groups with these and the rifle has a nice quiet firing cycle with them,as it happens they are very good in my bsa standard.another plus is the price at about a fiver a tin. atb