In praise of the old leather seal

[45flint]

I know we have made progress with better seals but I find the best seals to have in a vintage gun is the original leather. They just seem to hold up forever, that’s worth more than a few extra FPS. I’ve been extremely lucky to recently purchase some great old vintage guns. All I’m sure with their original leather seals. Weather warmed up to take my BSA Airsporter MK2 out and give it a go. Guns well over 50 years old just put some SAE 30 ND in when I got it. It’s shooting 550+ still right on original specs. Bought a 1930s Tell 2, still shooting fine after 70 years. I’ve purchased 5 Haenel 28s in the last 2 years, all never needed anything but some oil. Two Webley Straight grips one 90 years old same story. I have a FWB 65 with a modern material stop I had to replace, the original just crumbled out. I know leather can wear out but I just don’t see age being much of an enemy. Don’t have that comfidence with the seal in my Beeman R1?

[eyebull]

I must confess to a soft spot for the phosphor-bronze piston rings in some webley and FWB guns. They feel 'future-proofed' to me.

[45flint]

I must confess to a soft spot for the phosphor-bronze piston rings in some webley and FWB guns. They feel 'future-proofed' to me.

Yikes! I forgot, my old Webley pistols are those piston rings!

[Hsing-ee]

I like them but when manufacturers ditched leather and 'O' rings and took up nylon parachute seals like the Feinwerkbau Sport had been wearing since the early 70s power went up 25% and the running-in time dropped to a tin of pellets instead of 20,000.....

[45flint]

I like them but when manufacturers ditched leather and 'O' rings and took up nylon parachute seals like the Feinwerkbau Sport had been wearing since the early 70s power went up 25% and the running-in time dropped to a tin of pellets instead of 20,000.....

What is the life expectancy of the Nylon? Will it deteriorate with age?

[Hsing-ee]

What is the life expectancy of the Nylon? Will it deteriorate with age?

I think if you are careful with fitting them and don't go too mad on the sizing they will last for several years. The Feinwerkbau Sport ones will definitely turn into cheese after 10 years. So, no, they are definitely not as durable or forgiving as leather but they are far more efficient and they are not much money to replace when the time comes. A leather seal can be forced past razor-sharp edges, endure heavy dieselling, seal an out-of-round cylinder and last for decades on no lube (provided the seal has been well lubed at the beginning of its life) and can be replaced with a substitute cut from an old belt, so they have advantages. If they go hard and dry they can also be refurbished with a roughing up with a file and a soak in oil overnight. The smell of a leather-washered springer that is 'on song' and combusting oil at the right rate is delicious!

[bill57]

I converted my Webley Vulcan to a leather seal over thirty years ago; it's still on the same one, and is smooth and very consistent. My Ospreys are similarly converted.
As Hsing-ee says, leather is very tolerant of cylinder wall irregularity, but they need to be sized to a good fit. Usually a relatively loose fit works best, it should be very easy to push it down the cylinder. Too tight will rob it of power.

[Benelli B76]

I know we have made progress with better seals but I find the best seals to have in a vintage gun is the original leather. They just seem to hold up forever, that’s worth more than a few extra FPS. I’ve been extremely lucky to recently purchase some great old vintage guns. All I’m sure with their original leather seals. Weather warmed up to take my BSA Airsporter MK2 out and give it a go. Guns well over 50 years old just put some SAE 30 ND in when I got it. It’s shooting 550+ still right on original specs. Bought a 1930s Tell 2, still shooting fine after 70 years. I’ve purchased 5 Haenel 28s in the last 2 years, all never needed anything but some oil. Two Webley Straight grips one 90 years old same story. I have a FWB 65 with a modern material stop I had to replace, the original just crumbled out. I know leather can wear out but I just don’t see age being much of an enemy. Don’t have that comfidence with the seal in my Beeman R1?

Old type polyurethanes suffer from microbial degradation and basically disintegrate over a long period time. Some polyurethanes suffer from hydrolysis. Fortunately the new polyurethanes have additives to prevent this and will last far longer than the owner of the gun.

Baz

https://polymer-additives.specialche...n-polyurethane

[45flint]

Old type polyurethanes suffer from microbial degradation and basically disintegrate over a long period time. Some polyurethanes suffer from hydrolysis. Fortunately the new polyurethanes have additives to prevent this and will last far longer than the owner of the gun.

Baz

https://polymer-additives.specialche...n-polyurethane

How long have they been available in airguns?

[Benelli B76]

How long have they been available in airguns?

Interesting point. When I started work in polyurethanes in 1994 we were already using additives. There are two types of urethane, polyester and polyether. I think the polyester is more susceptible to bacteria attack. I have Weihrauch seals out of rifles over 20 years old and they are fully functional in good condition. It is difficult to know what material each manufacturer is using without asking for specs. I would think that all manufacturers use modified resistant polymers now.

Baz

[AC99]

Over the years I have acquired a number of Webley mk3's, two of which I had as a lad in the late 1950's. It was then I replaced the leather piston washers on both and they were used for a number of years before being stored and since then have had little use. Both will still hold air in the standard compression test (by cocking, raising loading tap and releasing trigger while holding cocking lever), no air leaking either past the tap or the washer. After almost 60 years both rifles have the same power as they did then.
On the other hand the polyurethane washer I replaced on my Original model 5 pistol four or five years ago has disintegrated AGAIN!
In terms of longevity it seems leather beats polyurethane hands down.

[bill57]

I suspect that the modern synthetic seal is the culmination of manufacturers attempts to move away from leather seals, which they wanted to do to simplify and speed up production. Webley tried piston rings and later the solid PTFE washer, BSA and others tried O-rings, and eventually the modern and almost ubiquitous "parachute" seal evolved.

Leather seals work extremely well, but require softening, sizing and lubricating to work. A synthetic seal, popped out of a mould, goes straight onto the piston and straight into the gun. From a manufacturing aspect it's no contest.

[Dan944]

This is all interesting stuff and I’ve enjoyed reading all these comments.

I converted my Webley mk 3 to a synthetic parachute seal years ago and it really smoothed the shot cycle out and is within 3fps with a certain pellet ,But this thread has made me want to try a leather seal on my 97 just to see how it feels? I currently run orings as just a test and I’m not liking it much, bit too snappy and quick. I like a soft shooting springer even if it is slower than a short stroke which I gave a few for Hft which are short strokes, but my 97 which I bought from New has always been snappy and harsh compared to friends 97s, so I’ve experimented for years trying all sorts, new cylinders, seals ect but I’ve never thought of trying a leather piston seal which would seem quite a crazy thing to do .......but I think when I get a bit of time on my hands I may just try it.

Atb
Daniel