Hi Guy
Sorry for the late reply.
I haven't got any pictures of any Tornado O ring conversions,
, but I do have some of the Relum junior piston I did which is exactly the same.
first off a bit of decapitation.
http://i1138.photobucket.com/albums/...s/DSCF1253.jpg
then I machined up the new piston head from brass, I machined it to take a standard BSA Meteor O ring and threaded the tail of the new head at 1/4" unf.
http://i1138.photobucket.com/albums/...s/DSCF1276.jpg
when the new head is fitted to the piston with a nylock nut it looks like this.
http://i1138.photobucket.com/albums/...s/DSCF1296.jpg
I used a Meteor MK5 spring and spring guide in the Tornado, though I think the Meteor MK6 spring could have worked better.
Jim Tyler showed a synthetic seal conversion in AGW where he used a 26mm Weihrauch seal on a homemade adaptor.
Hi Dave
If you need any help with the Fume Bluing give me a shout --- I'm always happy to help.
All the best Mick