 As aircraft became more advanced over the M16 's lifetime , its role as a mobile anti @-@ aircraft weapon became limited . During the Korean War , it served mainly in the ground @-@ support role , at which it was highly effective . In late 1951 , it was declared as " limited standard " and largely taken out of service from the U.S. Army in Korea , although a few examples served until the end of the war . It was declared obsolete by the U.S. Army in 1958 . 
