Chemistry help please

[WebleyWombler]

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?

[Ragle Jnr]

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

[trajectory]

If its made of an elastomer alcohol might well cause it to swell & exacerbate things a bit. I think hydrocarbons might do something similar......

[ccdjg]

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.

[WebleyWombler]

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.

Thanks for that tip sir.
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.

[pothunter]

Cellulose thinners contains Xylene, Butyl Glycol and Dichloromethane and is readily available, you could give that a try.

[edbear2]

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?

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

[steptoe1966]

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

[WebleyWombler]

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

Very good point. Noted, and thank you

[leetrenchard]

Take the acetone out and light the vapours at the transfer port.

Point in safe direction😁

[silva]

Have you tried the gentle application of a bit of heat !

[guitardan]

I put my Airsporter in boiling water, ten minutes, out it came..