PURPOSE: To obtain such an effect as if the amount of gunpowder is increased although a model gun is safe as usual, by giving power to a powder smoke gas out of a muzzle without increasing the gunpowder.

CONSTITUTION: A hole 3 for a barrel 1 is perforated near a muzzle 6 of the burrel 1, which is at the side of a gunpowder chamber, and a gas pipe 4 is fastened to the hole 3. A complete member wherein the barrel 1 is integrated with the gas pipe 4 is fastened to a model gun. At that time, the model gun is so composed that a high-pressure gas is sent into an entrance 5 to the gas pipe, that a powder smoke gas is sent into the muzzle 6, and that these gases do not flow upstream. However, it is necessary that processing being based on usual model gun regulations is done for a muzzle 2. Furthermore, it is necessary that a powder smoke gas-generating mechanism for the model gun main body and a high-pressure gas-jetting mechanism therefor are at a level being based on the usual gun regulations. In this way, such an effect as if the amount of gunpowder is increased although the model gun is safe as usual, can be obtained.