Metal casting is a manufacturing activity that uses metal and then melts it with a furnace. Meanwhile, aluminium casting is a technical activity by mixing several chemical elements which functions to see the right composition to increase the mechanical strength of the aluminium. This study uses sand molds. The results for the 10% Mn 5% Mg variation obtained a tensile test value of 128.15 MPa with a brinell hardness value of 21.81 BHN. The 15% Mn 7% Mg variation obtained a tensile test value of 99.62 MPa with a brinell hardness value of 19.65 BHN. And for the 20% Mn 10% Mg variation, it obtained a tensile test value of 116.47 MPa with a brinell hardness value of 19.90 BHN. This decrease can be caused by the inability of the alloy metal to spread throughout the microstructure and produce empty space in aluminium.