Abstract: An improved piggyback dispensing feature for extended dispensing devices of tile type having a housing with a downwardly extending handle, a trigger pivoted to the handle, an extension bracket attached forwardly of the housing, a barrel assembly attached to the extension bracket opposite the housing, and a piston rod slidably supported in the housing and extension bracket and protruding into the barrel assembly. The improvement comprises an interchangeable push-disk piston mounted on the distal end of the piston rod, and a smaller barrel assembly adapted to be seated inside the other larger barrel assembly to accommodate a smaller-sized cartridge. The smaller barrel assembly piggybacks in the larger, and the push-disk piston swaps out, thereby making it possible to use one extended gun for at least two different-sized cartridges, such as the typical ¼ gallon cartridges and {fraction (1/10)}th gallon cartridges.