Abstract: In the caulking gun disclosed herein, the piston of a caulking cartridge is driven by axial movement of a exteriorly threaded tube which is, in turn, driven by a rotating ring gear which is interiorly threaded to mate with the tube. The threaded tube is longitudinally split so that it can collapse out of engagement with the threads on the ring gear. A tapered plug cooperates with an expandable bushing inside the tube so as to hold the tube in engagement with the threads in the ring gear when the plug is in a first postion but, when the plug is moved to a second position, the bushing allows the tube to collapse thereby releasing pressure from the piston and allowing quick retraction of the split tube to facilitate loading of a new caulking cartridge.