Re-sizing a leather washer

[copperjacket]

Morning all.

I have had an old BSA apart to measure it for a new spring.

When I came to re-assemble it I found that the washer was a touch overtight - so much so that the pellet is not even consistantly leaving the barrel - a problem that wasn't there before the strip!

Do I:

A) Keep trying to shoot in the hope it will loosen up and cure itself.
B) Leave it for a couple of days to let it reform itself.
C) Strip it down and resize the washer.

Many thanks

[Rob M]

I'll have a 'B' please Bob...

[copperjacket]

I'll have a 'B' please Bob...

Ah the good old do nothing ploy..

Many thanks

[ggggr]

sure one of the experts will be along to tell you shortly but going to ask if you had the washer off or tightened the screw that holds it? Sometimes when made a washer I leave the screw a bit loose and then put the piston into the cylinder backwards before tightening the screw up. I then leave it over night to take shape. I sometimes leave the screw a touch loose when I assemble a gun and then when the piston (and the washer) have safely passed the threaded bit of the cylinder, nip the screw up with a screwdriver through the cocking slot.

[edbear2]

HI..You don't say if the washer is new or not?.......If new (or if stiff) you can size it easily by using a lathe and a sharp tool and finishing with glass paper, or just use a cordless drill and sandpaper if not.....If new, the washer should be an easy sliding fit in the cylinder (most replacements are oversized to allow for fitting).....The piston should be able to drop the full length of the cylinder under its own weight.....The BSA's of this period were built "dry"....ie. no oil on the washer*....once assembled, fill the loading tap with oil, stand the gun upright and close the tap, allowing the oil to drain into the cylinder......leave at least 24 hours...48 is better!

Have a look at the piston in this photo....the washer has been sanded and sized, and the piston bearing surfaces polished;

http://www.flickr.com/photos/3122848...7612687471706/

* I was told this by John knibbs, as he says, they wouldn't have been messing around soaking washers in oil on a production line, and the dry method is far easier to ensure that the gun beds in more quickly and seems to give more power due to less drag on the washer. If a second hand washer, you can still sand it to get the required fit if it is even slightly tight.

[copperjacket]

Thank you all for your advice.

The washer is not new - it has been in at least a couple of years and was originally sized dry then lubed - by soaking in Chambers ptfe enriched oil.

The gun has recently been apart for a new spring and when I refitted the piston I noticed the Washer retaining screw was not tight so I retightened and refitted. It may be that doing so has caused the leather to splay.

I was going to resize but thought it would be better to ask first.

It would seem a little trim may be in order.

Alternatively would I be better soaking the washer in say thinners to remove that oil, dry it then resize and use neatsfoot oil?

Edbear that rifle of yours looks magnificent. What is in the top of the photo - a sight?

[edbear2]

~Hi mate.....full set here;

http://www.flickr.com/photos/3122848...7612687471706/

It's one of 2 or 3 old BSA's I have scoped in the past......I was going to leave it shiny, but in the end I browned it with Birchwood Casey "plum brown"....and it ended up looking like this;

http://www.flickr.com/photos/3122848...7614265676462/

Re. the washer, there are as many ideas about lubing leather as there are types of air -rifle......I tend to stick with Cengar green oil.....it is a fairly light (about 30 weight) mineral oil, very close in composition to the old Webley oil I used as a nipper ........I grew up with slightly smoky, oil burning guns, and still believe that they run better like this...maybe I am a luddite

On my latest and most modern gun...a 10 year old TX200, I use just the lightest wipe of abbey SM50......but am convinced that anything silicon based should not be used in older, heavy steel piston guns.....just my own opinion.

[copperjacket]

Lovely photos

One thing missing is the spring - what did you use? I currently have one of Knibbs flat coils (32) in my Light Pattern.

[edbear2]

Lovely photos

One thing missing is the spring - what did you use? I currently have one of Knibbs flat coils (32) in my Light Pattern.

Hi......my Standards have either got Knibbs double sets (but for a 43" gun...his 45" sets are too long IMHO, or Airsporter springs, or in one, original NOS units)

My light models.....I find the Chambers flatwounds very smooth, or the Knibbs one is good as well.......In all cases, I find the Flat/oval wound Twin spring sets to give the smoothest action......they unwind unlike anything else, singles are good too, but in the long guns the the twin flat sets have such a different feel you can tell if they are fitted without looking underneath!

[copperjacket]

To clarify - the twin spring sets are they 2 different diameters one inside the other? Do you have a photo please?