Hi I have a BSA Mercury I bought used in 1983 and not touched for a long time. Today I dismantled it, the piston was dry, and initially stuck. I followed my nose and found the nylon piston head, retained by a pin thru it, and a rubber O ring, also a steel "ring" in a groove for it, above the O ring. Under the Nylon head a fibre sort of washer had disintegrated. I gave it all a good clean, made a replacement for the disintegrated part from a tap washer and with lithium grease reassembled it, it seems to give good power again. Looking thru parts lists and illustrations I find no mention of that steel circlip. What did you find in yours? I guess I should really track down proper replacement parts, O ring, the spacer (is it called a support) and breech seal.

I opened up my old meteor, it only has an O ring and a support for the piston head.

What do you know about that O ring?

I'm 4 years retired and playing, I bought my Meteor Super with my first tax refund, 1973. Still on all original parts and fun to use.

Cheers.

Added later. I read they used that steel ring to try to stop the piston swelling and jamming. Later Mercurys used an alloy piston head. Some people leave the steel ring off which seems like a good idea. THe washer that had fallen apart is called the buffer spacer. Kits out there for various different piston heads, the best one looks to us a "parachute seal" a lipped seal as i often see in bicycle pumps. Any advice, how did your Mercury go?

Sweet project by the sounds of it. Basic rifle, if you restored it it wouldnt be worth a whole lot. so agree; clean it up and try for performance.

Ive got a BSA mercury coming that has aparently got a seized piston - externally nice but buggered inside. so that will be a bit of a fun "get up and going" project

I have an old Gamo that is one of several unfinished projects and if it shoots any good when it's all together it'll go to my grandson.  It's cleaned up very well but the stock is what may be of interest.  It was originally coated with a mid-brown lacquer of some sort that was pretty scratched up.  I decided to have a go and stripped the bulk of it off with paint stripper (2 coats), then scraped off the residual and sanded it back to clean timber.

I then finished it with 5 coats of Trueoil applied with a small piece of cloth.  The finish isn't perfect but it's a hell of a lot better than what I started with.  It really wasn't hard to do and didn't take a great deal of time.

I think you need to show us the rifle... we're all keen to see a project take shape