Is it possible to thread a muzzle of a barrel without removing the action?

[tammons]

This is for a rifle that the barrel cannot be removed without destroying the barrel.
IE a relief cut would have to be made to remove the barrel.
And a re-barrel (at least for now) is not in the picture.
IE the rifle is a Swiss K-31 which is level 10 to rebarrel.

[bc160]

You bet, that's how most gunsmiths will do it. Shouldn't be an issue for any qualified smith.