Abstract: A pressure release mechanism for a calking gun adapted to receive a calking material containing cartridge tube and having a piston device for applying pressure to the tube for dispensing calking material therefrom enables the pressure to be released by the user to stop the calking material from flowing from the tube. The cartridge gun includes a ratchet device for advancing selectively and releasably the piston device, and the piston device includes a piston rod having ratchet teeth therein. The ratchet device includes a pawl and a latching dog for engaging the ratchet teeth. The pressure release mechanism includes a lever pivotally mounted near the latching dog for contacting it and moving it out of engagement with the teeth to free the piston rod. A manually operable device is connected to the lever and is adapted to be grasped by the user in a convenient manner for moving pivotally the lever to cause it to move the latching dog and thus to free the rod.