On my “reject” barrel the silver soldering was problematic, and one trunnion was subsequently glued into place with Loctite 620. This proved to be so effective, clean, and controllable that I used the Loctite for the main barrel. The following video shows the Loctited trunnions being machined, and showing no signs of being dislodged.
It also shows a possibly dodgy but successful method of rounding the ends of the trunnions.
Click on the arrow to see the 5″ video.