Quick change caulk gun - GIF

[Frank S]

The caulking cartridges around here (Australia) have a small ridge on the external surface at the "open end"...
but the device could also work by having a set of grippers which engage the plastic tube itself. - the ID of the tube is defined by standard size (and the plunger meets that with clearance), so a shallow spigot plug of that diameter would sit inside the open end of the cartridge, and a set of spring steel jaws could then press against the outer wall of the cartridge to grip it against the spigot... at least that is how I'd make my first attempt at making it.

That's same way I was thinking