Abstract: A dispensing gun for viscous materials comprises a stock supporting a push rod which is advanceable along a keep in which is mounted a cartridge of the material. The rod is advanced by means of a catch plate and trigger arrangement which bites on the rod and is retreated by a return spring. A release plate prevents the rod retreating with the catch plate. The release plate is frictionally engaged with the rod so that it acts as a lost motion brake once force is removed from the trigger. In this way the rod is allowed a limited retreat to take the dispensing force off the cartridge to prevent leakage when the trigger is not depressed.