There are several ways to do the barrels for switching. The factory setups for Hi Walls use a interrupted thread, with a small metal piece to mate the forearm and receiver together. This system makes the change quick, but not very solid, or accurate.
The Stevens system is one of the best, with it's set screw, but a cross pin system, with a tapered crosspin works equally well, and allows for faster changes. Schoyen and Pope both used the crosspin system on the guns they built barrels for. Although Schoyen also used the Stevens setscrew system as often. My Schoyen Ballard in .38-55, uses the Stevens setscrew system for barrel changes, and the barrel is just snug, so it can be changed easily.
Hope this helps.