  The magnetic properties of the Mn$_3$Ga$_{(1-x)}$Sn$_x$C, 0 $\le$ x $\le$ 1
antiperovskite compounds have been investigated in detail. Though all compounds
of this series crystallize in a cubic structure, the Ga rich (x $\le$ 0.2)
compounds transform, via a first order transformation, to an antiferromagnetic
ground state and the Sn rich (x $\ge$ 0.8) compounds exhibit dominant
ferromagnetic interactions at low temperature. In the intermediate range (0.4
$\le$ x $\le$ 0.7) co-existence of ferromagnetic and antiferromagnetic
interactions can be seen. The results have been explained to be due to growth
of ferromagnetic sub-lattice at the expense of antiferromagnetic sub-lattice
with increasing Sn concentration in Mn$_3$Ga$_{(1-x)}$Sn$_x$C. This growth
occurs to a point where the first-order transition is altered from a
ferromagnetic - antiferromagnetic type in Ga rich compounds to a paramagnetic -
ferrimagnetic type in Mn$_3$SnC.
