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I've just started work on a couple of BSA Meteor MkIV and a few Scorpion pistols. They have obviously not been used for years and the pistons/buffer washers are stuck solid.
I've always struggled with this type of job and have a sample of each stood up in a corner. One has the barrel and air chamber full of Isoprop. and the other Acetone. They have been like that for 2 days and still nothing is moving.
Is there any chemical I can obtain that will free off or dissolve the awful stuff that BSA make the bits out of.
I have removed similar stuck pistons on other guns by making wedge bolts but I son't want to do that with the BSAs because of their flimsy folded construction
Advice please?
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I knocked the piston out of my Scorpion pistol by using a drift in the cocking slot, once it gets moving it takes less effort! I vaguely recall ending up puncturing the nylon head on the last few inches, if I was to do another I'd make an impact tool to hook in the piston. Used ¾ tap washers to replace the cushion rather than the cheese BSA used! David
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If its made of an elastomer alcohol might well cause it to swell & exacerbate things a bit. I think hydrocarbons might do something similar......
Airgun Alchemist, Collector and Scribe
The most aggressive solvent towards polymers, apart from corrosives like acid and alkalis, is methylene chloride. If a 24 hour soak in that doesn't soften it up enough to make it movable, then you are stuck with brute force.
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Thanks for that tip sir.Originally Posted by ccdjg
I'll get some and try it. Failing that, I'll make a compression fitting for the muzzle and put them in the bath before connecting 200 bar to them, see if that works.Chemicals will be much easier if they work without eating the steel parts.
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Cellulose thinners contains Xylene, Butyl Glycol and Dichloromethane and is readily available, you could give that a try.
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Some of the big brands of paint stripper contained methylene chloride......& also alcohol of one sort or another, typically butyl alcohol.
Have you considered draining the existing acetone or Isoprop out then airing it for a while & then immersing it in a bucket of very hot water for a while then take it out & see if it budges while still hot?
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I have 5 to do. 3x scorpions and 2x meteors. 1 Meteor and 1 scorpion are soaking ATM. I'll drain them and try the hot water bucket suggestion on them tonight.
I have some xylene , so I will try filling the other Meteor tonight and leave to soak till tomorrow.
I've spent this afternoon making a concentric punch to produce the buffer washers out of some 6mm leather belting I have, 2x thicknesses of 3mm seem to produce the same job. Working with a spare cylinder and piston , I've also found the cheap 'o' rings size R15 (19x3.55mm) supplied in the Lidl red boxed multipacks to be a very nice fit. Just need testing.
Also made this afternoon is a steel mould to cast breech seal sized tube out of Shore 85. hardness casting rubber. Not sure whether that will work but I mixed and poured a few grams earlier and it will be cured off by tomorrow . Time and scrap materials cost cost nowt and I'm trying to keep costs down but still do an effective job. The proof will be in the testing
Thanks to those who have commented, I'll update when I'm done if anyone is interested
Hi, the Acetone works for me, but you have to put pressure on the piston as well I have found.....In the last Mercury I did I would sit and hold the barrel as hard as I felt safe to try and get things moving.....plus are you putting in through the transfer, or are you muzzle down and putting in the cocking slot, as obviously the latter gets to the buffer without the piston washer getting in the way!
So try muzzle down, good dollop of acetone, leave 1 hour then apply pressure / repeat worked for me, took maybe a full day whilst out in the garden aqnd just going back to the gun every so often, bit messy but the feeling when it "gives" is great
ATB, Ed
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Hi i had a mercury with a stuck piston i did get it free but forget how but someone did say have i tried putting a football pump needle in the port and just putting a little air in from the port end bare in mind it may not push the piston out but it may help a little but make sure you have the cylinder pointing away from you in case the piston does decided to shoot out , next time i am going to try it
stay safe
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Very good point. Noted, and thank youHi, the Acetone works for me, but you have to put pressure on the piston as well I have found.....In the last Mercury I did I would sit and hold the barrel as hard as I felt safe to try and get things moving.....plus are you putting in through the transfer, or are you muzzle down and putting in the cocking slot, as obviously the latter gets to the buffer without the piston washer getting in the way!
So try muzzle down, good dollop of acetone, leave 1 hour then apply pressure / repeat worked for me, took maybe a full day whilst out in the garden aqnd just going back to the gun every so often, bit messy but the feeling when it "gives" is great
ATB, Ed
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Take the acetone out and light the vapours at the transfer port.
Point in safe direction😁
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Have you tried the gentle application of a bit of heat !
"helplessly they stare at his tracks......."
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I put my Airsporter in boiling water, ten minutes, out it came..
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Well the soaking scorpion and Meteor have both come out with a little persuasion but only after putting a little solvent in each piston chamber and standing in a galvanised bucket of boiling water for 10 minutes. before the additional solvent , the boiling water alone wouldn't shift them with the amount of force I wanted to use.
I'll try the other methods on the other 2 scorpions and the meteor that's left for interests sake (and I'm lazy so always want to find an easier way)
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