Attention all Webley Longbow Guru's

[Shed tuner]

smooth it out, it's not going to seal otherwise

[ashf9999]

Agreed. It really needs a hone and polish, but watch that the minimum of material is removed. Unless you’re very confident and have the tools, maybe find a local engineering company. Hopefully the parachute seal will take up the slack sufficiently.

[rapidresponse1]

not seen that before

[mattyw1987]

I’ve got a spare Aussie piston seal that are a bit snugger than original bud and way better so if you end up needing one let us know.

Cheers.

[maximus]

Is there a step between the two finishes? If not it might just be discolouration of the original blued finish where the piston has been running, though it is unusual. If there's no step, no burrs and no scoring where the seal runs then it should be ok really but a light polish with some 400 grit wet and dry won't do any harm.

[Jonnymac]

I’ve got a spare Aussie piston seal that are a bit snugger than original bud and way better so if you end up needing one let us know.

Cheers.

Thanks buddy. I got a purple one from chambers, but if that one is better, I could be interested. What did you want for it?

[Jonnymac]

Is there a step between the two finishes? If not it might just be discolouration of the original blued finish where the piston has been running, though it is unusual. If there's no step, no burrs and no scoring where the seal runs then it should be ok really but a light polish with some 400 grit wet and dry won't do any harm.

No step between the two. It definitely doesn't look like discolouration. You can see the joining line very clearly.
I have decided, in the absence of any more info, to do a light wet and dry on it, to remove the high spots.

[weebster]

Could it be someone has experimented with copper slip grease?, the kind used for rear of brake shoes on motors, it would certainly explain the start/stop lines, it looks to me its some kind of residue left behind which would point to something having been applied to the piston

[Murphy]

Show us a picture of where it says longbow on the cylinder.

[Jonnymac]

Show us a picture of where it says longbow on the cylinder.

[evert]

So what is the overall consensus?
Do I try and smooth it out with some wet n dry?
Or leave it as is, allowing the Moly grease to sit in the microgrooves?

Looks to me like bluing discoloration.
How does it feel when you push a sealed piston on and down the compression chamber?
Dad has a Birmingham made Tomahawk of the same vintage that has a very rough compression chamber surface,
it has what seems to me machining ridges.

Tubes like this really need a brass plug hone.

[Thegreg]

That’s an interesting one. I don’t believe it’s a sleeve or a liner, but discolouration like others have mentioned. The radial machining lay is no different to the blued section of the tube, the colour will just be highlighting it.

It’s the definitive boundary that’s odd. Does that line coincide with where the rear part of the piston stops? Maybe thinking it could have deposited there if someone had modified a piston with bronze rings or similar.

Copper sulphate solution does deposit a light copper coating on mild steel. I can’t think why it would come near an air rifle cylinder though.

Cheers
Greg

[Jonnymac]

That’s an interesting one. I don’t believe it’s a sleeve or a liner, but discolouration like others have mentioned. The radial machining lay is no different to the blued section of the tube, the colour will just be highlighting it.

It’s the definitive boundary that’s odd. Does that line coincide with where the rear part of the piston stops? Maybe thinking it could have deposited there if someone had modified a piston with bronze rings or similar.

Copper sulphate solution does deposit a light copper coating on mild steel. I can’t think why it would come near an air rifle cylinder though.

Cheers
Greg

No, the piston is completely standard, as was the rest of the gun. It even had the black plastic, Webley spring guide in.
I get what you are saying about the machining lay, but it seemed to have a slightly different surface texture.
Anyway, in the end I took a bit of dowel and some 400 grade wet and dry, and smoothed it out a little. I added Welsh Willy spring and guide kit and a new seal.
It does shoot much better now. No twang, that it had before and much less harsh firing cycle. smoother to cock also. I am sure it is still settling down as I have only put about 30 pellets through it, so far.
I will start to chrono it after another load of pellets and see what it settles down to.