Tx200hc .177 to .25/.22/.20 calibre change

[Shed tuner]

Do you remember the thread dimension?

I think it's 14 x 1 mm, but would need to check...

[evert]

I think it's 14 x 1 mm, but would need to check...

Thanks. My Lathe only has imperial threads, so the TX barrel stays in place then

[Garry]

As above, is it as uncomplicated as swapping the barrel or would the spring need changing and then tuning.
Thanks.

That made me smile, I'd have thought the spring would be the uncomplicated part

[Shed tuner]

Thanks. My Lathe only has imperial threads, so the TX barrel stays in place then

So does my Portass lathe, but I did some calculations and CAD'd up then 3D printed a compound gear in ABS (something weird like 60-47 tooth) that got me a 1mm thread pitch within 0.2%

Also if you are machining a new barrel, you can use whatever (fairly fine) thread pitch you like, so long as you source/make a matching nut. Something common in the 24-28 tpi range would work perfectly. Opening out an existing nut is the easiest route, as the nut needs to be quite small relatie to the thread diameter anyways, to allow plenty of clearance for a socket.