Senior down on power

[felix gunner]

Been testing mine and it's well down for some reason.

Bruce gives 416 fps in .177 and 330 fps in .22 for what it's worth.

Nothing has really changed since the last time tested (2015 following new genuine spring) when it was very healthy, averaging (Hobby 7.0) 470 fps + and 3.45 ft lbs) - this was with the .177 barrel.

Since then I have used it pretty infrequently but with a .22 barrel only.

Tested yesterday (Hobby 11.9) it was doing a meagre 246 fps and 1.6 ft lbs.

I replaced the .177 barrel but no better down to 306 fps and 1,46 ft lbs.

So power down 50% somewhere?

Piston ring looks fine and all is lubed correctly.

I stripped it again and relubed the piston ring and this gained about 45 fps in .177 but maybe still dieselling a tadge so not sure if it did much.

I tried the trick I read of sucking on the barrel and then trying to get a vacuum on your tongue but it did not work for me. (...with the barrel closed against breach seal (and unloaded) suck strongly at the muzzle. Put your tongue against the bore. It should stick if there's no pressure leak. If it doesn't, it means you might need to replace the seal to cause a full seal of air.)

Also tired holding tissue over the breach seal but hard to say if it moves due to a leak as it jumps of course.

Blooming frustrating.

[Benelli B76]

You are taking for granted that the spring has lost no power over those years just because you have not used it very much.

Baz

[felix gunner]

Thanks for the reply Baz, had a lot of views and no other responses - does seem quiet on here, don't know where all the Webley nuts have gone that would have chipped in in years past!

I don't suspect the spring though to be honest, it has only been in there a very relatively short time, little used and always left uncocked and I've got much older springs which are fine. I'll pop an older one in though to see.

Not sure how well the vacuum sucking thing on the barrel should work as not tried it before but the Breech seal looks good and interfaces well.

I'm sure it the piston ring but that was new some years back.

I do love the Senior but it is frustrating - always something with these guns, can never get them all running right together...

[wild boar]

could the barrel have gone a bit rusty ? maybe a good clean would help it

[Fronteria]

I had a senior which I purchased at auction that was very low on power. I eventually traced the cause to the piston ring not because it was worn or broken the ring had been replaced and was binding because the ring gap was wrong, the cylinder had a taper of a few thou. causing the ring gap to close up completely then the ring would bind on the cylinder wall causing it to slow the piston speed down an inch or so at the end of it's stroke when you fired it.
I filed a few thou off ends of the ring, power restored to normal range.
It might be worth you having a check just in case you have the same problem.

[ggggr]

Been testing mine and it's well down for some reason.

Bruce gives 416 fps in .177 and 330 fps in .22 for what it's worth.

Nothing has really changed since the last time tested (2015 following new genuine spring) when it was very healthy, averaging (Hobby 7.0) 470 fps + and 3.45 ft lbs) - this was with the .177 barrel.

Since then I have used it pretty infrequently but with a .22 barrel only.

Tested yesterday (Hobby 11.9) it was doing a meagre 246 fps and 1.6 ft lbs.

I replaced the .177 barrel but no better down to 306 fps and 1,46 ft lbs.

So power down 50% somewhere?

Piston ring looks fine and all is lubed correctly.

I stripped it again and relubed the piston ring and this gained about 45 fps in .177 but maybe still dieselling a tadge so not sure if it did much.

I tried the trick I read of sucking on the barrel and then trying to get a vacuum on your tongue but it did not work for me. (...with the barrel closed against breach seal (and unloaded) suck strongly at the muzzle. Put your tongue against the bore. It should stick if there's no pressure leak. If it doesn't, it means you might need to replace the seal to cause a full seal of air.)

Also tired holding tissue over the breach seal but hard to say if it moves due to a leak as it jumps of course.

Blooming frustrating.

I would think it is the breech seal especially if it is a leather one, which may need lubing and a chance to swell up. However, for ease and a methodical approach, if you have another Webley pistol, chrono that so you know the mainspring is ok, then try it in your Senior and see if your Senior is close to those readings. If it is, then it is probably the mainspring. If not then you are looking for something else. I cannot see it being the seal on the piston being tight as that should not have changed over time.
BUT--and I know a few people have done this , strip the gun and remove the piston and shine a torch down the cylinder and see if there is any debris in the cylinder. Then use a bit of thin wire, and poke through the transfer port and hopefully you should see the wire coming into the cylinder. If it does not show or seems difficult to come through, then you probaly have a small bit of rag or kitchen towel in there from when you have cleaned the cylinder out. Please let us know how you go on.

[felix gunner]

Thanks chaps - breech seal is a genuine Nitrile and in (to my eyes) perfect condition. I've had this pistol apart a month of Sunday's and very familiar with it's insides which as per the 'stiff to cock' topic are mirror like and very blemish free. Super clean and greased where they should be. Pushing the piston in/out by hand it *feels* about right in terms of resistance/drag.

I'll try the spring from my MK 1 as that had a new genuine spring at the same time and is a gem - putting out .22 Hobbys at 348 average with spread of just 6 and 3.20 ft lb.

I have never thought the piston ring a great idea - I know some have tried a nitrile O ring but it seems sacrilege. I much prefer the leather washer in other Webleys.

[felix gunner]

Update - dismantled - try as I might, by blocking breech seal or barrel with finger when held in place and pushing back piston with long rod - no compression or resistance. Strange as noted the piston/ring seems to have a nice feel of slight drag.

I found a combo of small O rings which would fit in the cylinder tightly but still move (most are too thick) and repeating above there is now compression and an air spring effect.

This even though the PB ring looks perfect and was a genuine Webley (bough it with some other spares from Denis H may moons ago) and was working fine previously.

My preference as the best solution would be to maybe mill/thread the end of the piston to take a leather cup washer?

What do you think?

[felix gunner]

Further update - chronoed with the nitrile rings - better but not great - after a few shots dropped to around 370/380 with .177 Hobbys. Was doing 470 when new spring fitted a thousand or so pellets back. And that still had the same piston ring. Bloody things!

I'll try the MK I spring and report back...