Abstract: An elongated horizontal barrel, transfer tube and cylinder are provided in vertically laterally stacked relation with the barrel disposed uppermost and the cylinder disposed lowermost. Closure structure is provided for the rear end of the barrel and the rear end of the barrel and transfer tube are in closed communication with each other while the forward ends of the transfer tube and cylinder are in closed communication with each other. The closure structure is shiftable to a position opening the rear end of the barrel and the rear end of the barrel may receive a blow dart therein after which the rear end of the barrel is closed. A piston is freely slidable within the cylinder and elastic tubing structure is provided for yieldingly biasing the piston forwardly within the cylinder and cocking structure is provided whereby the piston may be manually displaced rearwardly in the cylinder against the biasing action of the force structure.