Wouldn't it be nice if manufacturers provided a complete list of the O ring sizes used on their guns? I know you can usually find the sizes via a Google search or by asking on the BBS but it would be nice to be given the BS or metric sizes in the manual. The thought came to me when looking for a breech seal for an Original 66. I found, somewhat by trial and error, that a BS109 is a very good fit; the same size as used on a Theoben Fenman.
An Air Arms TX200 breech seal is a BS108 and as far as I can remember, the size is given on the Julian Bond spares site. But I think that site is unique in giving the seal types and sizes ... thank you Julian.
Just thoughts from a Victor Meldrew impersonator .....
Cheers, Phil