A caulking gun has a tubular chamber to surround sleeve-like rigid tubes and compressible sausage type containers containing viscous materials including sealants, adhesives, caulking, mastics and the like. When rigid tubes are loaded into the chamber, compressed gas is allowed to surround the sleeve and a plunger loaded within the rigid tube to equalize pressure around the outside of the rigid tube. If a sausage type container is loaded into the chamber, a removable plunger is also provided to form a tight seal between the perimeter of the plunger and the inner surface of the chamber. Compressed gas introduced into the chamber preferentially acts on the plunger and an underlying end wall of the sausage to expel the material, without imparting any significant pressure to other parts of the sausage. The caulking gun includes a variable flow rate nozzle which may be removed from the device. The nozzle may be replaced with similar or different nozzle pieces of various shapes and sizes, if desired. Hand operated controls vary the flow rate through the nozzle and control introduction of compressed gas when in use. These features may be incorporated into other portable, hand held dispensing devices powered by other pressurized fluids.