PURPOSE: To provide a low entire height of a gun and to enable the gun to be transported on the land by a method wherein a bullet box is fixed and disposed at a position different from a turning shaft of a main body of the gun and a bullet supplying slip ring is arranged at an intermediate between the main body of the gun and the bullet box.

CONSTITUTION: A bullet supplying slip ring 6 is arranged coaxially with a turning shaft of a main body 1 of a gun below a gun frame 2. A bullet box 17 fixed to a bullet box fixing table 18 arranged on a base block 4 of a tracting trailer is disposed at a position different from the turning shaft of the main body 1 of the gun. Accordingly, even if the bullet box 17 is made large through a large diameter setting of the main body 1 of the gun, it does not accept any influence from the bullet box 17, an entire height of a machine gun can be reduced low and the gun can be made into a retracting type trailer machine gun which does not provide any trouble in a land transportation. A tire 25 of the retracting trailer can be lifted up and openable or closable supporting legs 27 and 28 are disposed, so that a center of gravity of the machine gun can be set low when a machine gun firing occurs and then a stable shooting can be carried out.