Switch barrel barrel stubs can be made from the H&R, T/C Encore, Contender, CVA Apex and a few others.
Short and to the point - here is an H&R set up as a switch barrel, with the included barrel lock nut and pin. Either a pin or spanner wrench can be used to remove and or tighten the barrel lock nut, which takes minimal pressure to lock a barrel firmly in place. I have work to do, so I will let the pictures speak for themselves, and as always, if you have any questions, just ask!
Oh, before I forget, a switch barrel barrel stub can easily be set up for Savage pre-chambered barrels, which saves both time and money.
And yes, there is a cartridge size limit on doing these...