Webley Senior main spring

[nikvanorton]

I've noticed that the mainspring supplied by John Knibbs is quite a lot shorter than the ones in the pistol (about an inch). I've replaced a couple of old springs with these and they have resulted in a bit of a loss of power.
Is this the only replacement available or are there other suppliers that have springs more like the original size?

https://www.airgunspares.com/catalog.../category/906/

[WebleyWombler]

How long is the original spring and what is the length of the new springs please? The springs you have from Knibbs sound like Typhoon springs

Also bear in mind that Seniors do not really get on with modern lubricants in the piston ring /cylinder area. A good dose of SAE 30 engine oil generally ensures maximum power .

[isobar]

i bought a spring from protek for a mk1,very similar to an original in length and performance.

[Troubledshooter]

I have new Senior springs with tags on, and not one is the same length as the next, although the differences are not massive.
There was a thread on this a while ago, in which a photograph of John Atkin's collection of new springs showed similar disparities on length.
Below is John's text:

Webley Senior Mainsprings – JA - 10/02/2019

The Webley ‘Senior’ officially used a 37-coil mainspring, unchanged in coil numbers since pre-war days when the Senior took over from the Mark II Target Model de luxe air pistol, which, like the Mark I used a 36-coil mainspring. The added length of the one extra coil, coupled with reduced friction of the new single phosphorous-bronze piston ring of the Senior, boosted the power from the 350 f.p.s. of the Mark I/Mark II to 360 f.p.s. in .177" calibre.

With the the right pellet and mainspring, it’s true some tuned Seniors can exceed 430 feet per second. In the late 1930s, Webley gave a mean muzzle velocity of 416 f.p.s as an official figure for their .177" pre-war Senior. Velocity testing using several 1940s and 50s Webley Seniors prove Webley’s advertised 360 f.p.s. as more of a correct average.

The Webley Senior mainsprings shown come from different eras. The oldest, longest and most powerful at the top. Although they should all be 37 coil mainsprings, some are 38 or even 39 - whilst a couple are only 36, 7 inches long and I’d have assumed they were for the Mark I or II - apart from the attached sealed tin tabs marked "S.A.P." (Senior Air Pistol) which have been on them since I purchased them in 1975 for 33p each from the ever-patient Miss J. Partridge of Webley’s Spares Dept. It wasn’t wrongly tabbed at the factory - mainsprings S8 (Senior); M7 (Mk. I) and M.7 (Premier) were all made the same size by then, as part no. ‘P1032’ common to all three pistols and producing a reduced 350 f.p.s. in the .177" Premier’s published data of the time.

To sum up, fitting a later Webley no. 1032 mainspring to an early Senior won’t give a true reading of the original higher power but the likelihood of finding the right ‘new’ early 1930s spring as per those sitting on the old-style blue box are remote.

[nikvanorton]

Thanks for all the info - the sprimg from Knibbs is about 6.25 inches long.

[WebleyWombler]

Thanks for all the info - the sprimg from Knibbs is about 6.25 inches long.

That's about 1/2" shorter than a Premier spring and 5 /8" shorter than a Senior spring. A Junior spring would be 6.5" long and have about 30 coils.

Something not correct about the one you have been supplied with. Have you contacted Knibbs?

Sounds like you would be better off with the W25p spring from Protek Supplies . It's a little bit long but works very well in Senior models