RIC barrel bushing/sleeve

[Bruce_in_Oz]

Silver solder os great stuff, but you have to be REALLY careful not to overheat things with the torch and cause evil things to happen to the bore at the muzzle.

One old trick is to pack the relevant section of bore with charcoal and then SOFT solder, after thorough cleaning, fluxing and tinning the barrel and the interior of the collar.

I'm sure there are folks MUCH more "crafty" than I am, who can provide greater detail.