Abstract: Discloses a caulking gun apparatus including a caulking cartridge housing, a handle with a trigger attached to the housing, and a pawl system to ratchet a plunger rod and displacement head into the inlet of a caulking cartridge. A plunger rod release mechanism is provided which can be actuated by the operator while the caulking gun is held and operated with one hand. Mounted within the housing is a piercing blade and sealing mechanism for piercing the closure diaphram of the caulking cartridge and thereafter stopping the caulking cartridge to seal the caulking cartridge between the times that the caulking compound is extruded from the cartridge through its nozzle. A plurality of holes of different size as defined in the handle of the gun with the holes being oval or elliptical in shape and having their edges bevelled as to form a sharp edge on the inner side of the handle to act as a shear with a cooperating edge of the trigger when depressed into the handle.