Quote Originally Posted by oliver13 View Post
Just a footnote really, but the compression tube on my Mk6 had a distinct line of silver coloured brazing visible at the join with the breech. I've always assumed it was silver solder,
It may be wise to confirm exactly what it was before you braze on a new barrel & the compression tube comes off...

What about a mechanical solution with removable barrel fitted into a rebate a bit like the old Webley Hawk's, with a screw to secure it. You could have .177, .22 & a .25 barrel for special occasions?

I think the tap loader would need to be changed for different calibres which would make it a bit fiddly, but making a rebate would work and a grub screw to lock it similar to how a Rapid barrel fits would be a good idea, and you could have different barrel lengths to experiment with, and different manufacturers barrels.