A caulking gun having a push rod-formed by two interlocking chains. The caulking gun comprises a barrel having an open framework for receiving and cradling a caulk cartridge. A self-contained drive mechanism is provided to forwardly advance a chain arrangement comprising two separately coiled chains, each composed of a series of individual links connected in pivotable fashion one to another. The shape of the individual links of the two chains enables them to be interlocked as one parallel chain, forming a push-rod to compress the caulk cartridge, for extrusion of material contained therein. The coiled chains enable the chain arrangement to bend 180 degrees, so that the overall caulking gun length is reduced. The caulking gun is preferably made entirely from plastic. A caulk cartridge is retained within the barrel of the device by a pair of locking clips which may be closed by a sliding ring mechanism.