Thanks Mick ... excellent information.
But this reminded me of thoughts I have often had. This is one of those instances where it is possible to swap and change one manufacturer's parts, breech seals, piston seals etc for those of another manufacturer. Mainsprings are an obvious case in point and no one bats an eyelid in thinking about it or trying it. But other parts e.g. breech seals seem to attract scant attention. I try to keep notes on information I find on here but it would be wonderful if people posted their experiences of parts compatibility.
Just a thought, and not wishing to hijack this very interesting topic. Maybe a 'sticky' for the experiences. But maybe it would not get much use ....
Cheers, Phil