Seized piston

[Vernal]

I haven't shot my Lincoln Jefferies for a year or so, so a few of days ago I put a couple of drops of leather oil in the tap (new John Knibbs leather washer a couple of years ago), and decided today to try a few shots (I can shoot from the cover of a shed). The gun completely refused to cock, as the cocking lever opened and came across a solid stop. I stripped the gun to investigate, and the piston is totally, and I mean totally, (a decent tap with a mallet on a block of wood inserted in the cocking slot will not budge it a fraction) solid. The gun is stored in a warm dry room, and there is no rust externally or, as far as I can see, internally, so all I can think of to cause the seizure is an expanded and jammed washer. Can any one tell me please whether this can happen and, if so, (or indeed if not) offer suggestions on how to free it? Heart is the only thing I can think of, but how much, or will heat make the leather swell even more?

[trajectory]

I haven't shot my Lincoln Jefferies for a year or so, so a few of days ago I put a couple of drops of leather oil in the tap (new John Knibbs leather washer a couple of years ago), and decided today to try a few shots (I can shoot from the cover of a shed). The gun completely refused to cock, as the cocking lever opened and came across a solid stop. I stripped the gun to investigate, and the piston is totally, and I mean totally, (a decent tap with a mallet on a block of wood inserted in the cocking slot will not budge it a fraction) solid. The gun is stored in a warm dry room, and there is no rust externally or, as far as I can see, internally, so all I can think of to cause the seizure is an expanded and jammed washer. Can any one tell me please whether this can happen and, if so, (or indeed if not) offer suggestions on how to free it? Heart is the only thing I can think of, but how much, or will heat make the leather swell even more?

I'd be interested to hear what others may say but I've seen & heard of rusty seized guns, synthetic piston washers & buffers swelling etc causing jams or lock ups, old oil & grease can congeal & jam mechanisms but a looked after gun with a seized piston caused by the leather washer is a new one to me. I suppose my first question would be have you ever taken the piston out before & hence know for sure it has a leather piston washer & not a man made polymer conversion by a previous custodian. If it is a leather one I'd be surprised if it has swollen to the point it has locked up. Maybe there are some circumstances where that is possible but as I say I've not encountered it. Another remote possibility, has the cylinder been bumped, it would need a fair bump but if it's gone out of round that might be enough to prevent the piston moving.
If its a swollen leather washer then. When you mentioned stripping the air rifle was that trigger block off & spring out when you tried moving the piston?

I suppose a little warmth on the cylinder is worth trying, nothing too hot, maybe a hot water bottle in a towel & see if that frees things up a bit. Maybe try that & see if it works. I'd not suggest anything else yet as any materials or substances introduced could affect a following stage. So I'd suggest one step at a time. Someone might suggest a high pressure airline down the muzzle, maybe it's a possibility but try some gentle warmth before thinking of anything else.

[Hsing-ee]

I hope no silicone oil has been involved.

This locked solid a tap on a taploader I once had, and it was very tricky getting it free again.

I'd be inclined to remove the stock, close the tap and get a small funnel and pour a 50/50 mix of acetone and Automatic Transmission Fluid into the barrel, it should then seep into the compression chamber. Allow to stand for 24 hours then wipe off, replace the stock and try cocking it again. Once the gun is freed up, DO NOT FIRE IT, strip, clean, degrease and relubricate,
reassemble and carry on.

[Vernal]

Thank you for the advice gentlemen. The strip is indeed block off and spring out. It is definitely a leather washer, I fitted it myself 2 or 3 years ago, and unless John Knibbs put silicon in their leather oil no silicon has ever been anywhere near any of my guns. I have never done anything to cause the cylinder to go out of round, and there is no sign of damage on the exterior. The gun was firing nicely last time I shot it, about a year ago.
I agree with one step at a time, and tomorrow I will start with a little gentle heat. perhaps a heat gun on low setting, before i move on to solvents. I don't have automatic transmission fluid, and thinking more about white spirit to soften the oil?
Another thought is a screw type extractor to hook into the cocking slot and pull against a leather protector over the end of the cylinder?

[Hsing-ee]

Thank you for the advice gentlemen. The strip is indeed block off and spring out. It is definitely a leather washer, I fitted it myself 2 or 3 years ago, and unless John Knibbs put silicon in their leather oil no silicon has ever been anywhere near any of my guns. I have never done anything to cause the cylinder to go out of round, and there is no sign of damage on the exterior. The gun was firing nicely last time I shot it, about a year ago.
I agree with one step at a time, and tomorrow I will start with a little gentle heat. perhaps a heat gun on low setting, before i move on to solvents. I don't have automatic transmission fluid, and thinking more about white spirit to soften the oil?
Another thought is a screw type extractor to hook into the cocking slot and pull against a leather protector over the end of the cylinder?

This is really weird. I can only think a spot of corrosion has locked it up and obviously you haven’t put main force on it, but it might yield with a little encouragement. Maybe a good squirt of WD40 from the cocking slot side and in through the transfer port could free it off? I’ve never heard of leather sticking in a chamber, typically it might go hard and dry but won’t actually glue the piston in like for example BSA and FWB synthetic piston washers … Hope you get it sorted and I’m curious to know how the jam came about ..

[edted]

I have had the same thing on a couple of rifles in the past .
My solution was to put them in a trough and fill with diesel, after a week the pistons came out with ease.

[Vernal]

No progress this morning. I tried very gentle heat (still comfortable to touch) and a better set up with a steel bar (and protector) which let me give it a pretty decent whack with a dead blow hammer, resulting in absolutely no movement at all.
For the next step I have put a fair quantity of meths down the muzzle with the tap shut, and I will give it a few hours before I resume hostilities. I am resigned to having to replace the newish washer, so using a more aggressive solvent like diesel, or more heat and destroying the washer remain options for later if needed.

[trajectory]

Sorry to hear its not shifted yet.

My next stage would be to soak it in some form of fluid that might help free it up. Either by introducing it though the barrel/loading tap & the cocking slot simultaneously or immersing the whole thing (minus stock, trigger block & spring in a trough of something.
Depending what materials you have to hand might determine what you can use but I'd shy away from WD40, it's good stuff but if it dries out it seems to leave a layer on the surface almost a dry film? I think I would put something down the barrel or loading tap maybe 3in1 even paraffin or diesel, but soaking in a trough of diesel would be a godd idea if you have a suitable container. Give it a slosh around in the trough to displace trapped air, but it will probably find its way into all the nooks & crannies by itself.

The idea of pulling on the piston with a hook & protecting the end of the cylinder at the same time sounds a fair bet but I think it would be better to get the piston freed up by soaking first, maybe a mechanical pull will be necessarry to get it moving but I'd go at it in stages with minimal force first. Perhaps it will need more oomph later on but at the moment early days so patientce & care & if it can be avoided ......well that just sounds a bit better to me,
ATB

[Waddy]

I bought an old airsporter in bits & there was a fair amount of old leather seal "welded" to the end on the chamber, which sounds like what yours has done.

The bits came off with brake cleaner & rotating the end of a stiff cardboard tube that had been part of the packaging for cling film.

Id either go with a solvent or something like Neatsfoot. Oil does dry hard, and sticks like "something" to a blanket, which is why paint is made with it.

Heat isn't going to help IMHO, and I'd be vary wary of brute force.

.

[Vernal]

Solvents seem to be the way to go, and thanks for the various suggestions. I will top up the already applied meths and give it 24 hours before I try again, and if it doesn't work, try what I have a available. White spirit and neatsfoot are to hand, but I wonder if penetrating oil might be better? Are there any risks with this?

[Shed tuner]

Solvents seem to be the way to go, and thanks for the various suggestions. I will top up the already applied meths and give it 24 hours before I try again, and if it doesn't work, try what I have a available. White spirit and neatsfoot are to hand, but I wonder if penetrating oil might be better? Are there any risks with this?

the only thing that might get damaged is the seal, which is cheap and probably already toast. Like others have said, soaking in some kind of solvent, like diesel, is the way I'd go.

It really is weird though, for it to seize so solid when in good mechanical order and kept dry. was there any plastic disc behind or within the piston seal ?

[Hsing-ee]

Solvents seem to be the way to go, and thanks for the various suggestions. I will top up the already applied meths and give it 24 hours before I try again, and if it doesn't work, try what I have a available. White spirit and neatsfoot are to hand, but I wonder if penetrating oil might be better? Are there any risks with this?

The acetone/ATF mix is an oldschool mechanic's penetrating oil potion which works brilliantly on rusted bolts and so on, the acetone brings the oil into where it needs to go. Probably you can mix acetone with motor oil (some use medium weight motor oil as a lube in springers) and use that instead. As far as I know WD40 is largely paraffin so it evaporates. Meths is just ethanol like you get in vodka, with an additive to make it taste foul. It will just dry out the leather further as far as my chemistry informs me.

[Lawrie Amatruda]

I haven't shot my Lincoln Jefferies for a year or so, so a few of days ago I put a couple of drops of leather oil in the tap (new John Knibbs leather washer a couple of years ago), and decided today to try a few shots (I can shoot from the cover of a shed). The gun completely refused to cock, as the cocking lever opened and came across a solid stop. I stripped the gun to investigate, and the piston is totally, and I mean totally, (a decent tap with a mallet on a block of wood inserted in the cocking slot will not budge it a fraction) solid. The gun is stored in a warm dry room, and there is no rust externally or, as far as I can see, internally, so all I can think of to cause the seizure is an expanded and jammed washer. Can any one tell me please whether this can happen and, if so, (or indeed if not) offer suggestions on how to free it? Heart is the only thing I can think of, but how much, or will heat make the leather swell even more?

Is it possible to drill out a piece of round bar with a hole to fit over the centre rod of the piston, and fit a grub screw through the side to grip the centre rod through the cocking slot, then you could try pulling it out, just a thought.

Cheers Lawrie.

[keith66]

WD40 is about the worst penetrant for releasing stuck things there is. Us Diesel, ATF & acetone or proper penetrant like plus gas or similar.
Use a Brass or bronze drift on the piston rather than steel or you will mash it up.
If all else fails a grease gun on the barrel will shift it but you would need an adapter made & clamped to the barrel end with nipple to attach the grease gun to.

[Vernal]

Is it possible to drill out a piece of round bar with a hole to fit over the centre rod of the piston, and fit a grub screw through the side to grip the centre rod through the cocking slot, then you could try pulling it out, just a thought.

Cheers Lawrie.

Nice thought for a way to do it, but I need to get some sort of freeing first. It feels totally solid, almost as if there is a solid mechanical lock in.