 The M16 was an improvement on the twin .50 caliber M2 Browning heavy machine gun equipped M13 MGMC and M14 MGMC ( built on an M3 and M5 Half @-@ track chassis respectively ) . It was based on an earlier model of the M13 ( the T1E2 ) , but the M33 Maxson mount was replaced with the M45 Quadmount and the M2 Half @-@ track chassis was replaced by the M3 chassis . 
