It is heavy, 23 lb. as I recall, and no really comfortable way to carry it either. The ammo weighs a ton too. It has been replaced by the M-240B, which is actually even heavier at 27 lb. but the 240B has a much higher rate of fire and maximum effective range. It's really meant to be a crew-served weapon and too heavy for squad-level dismounted patrols, which is probably what your dad was doing. The army came up with the M249 SAW which is much lighter to fit that role.

__________________
"He writes the worst English that I have ever encountered. It reminds me of a string of wet sponges; it reminds me of tattered washing on the line; it reminds me of stale bean soup, of college yells, of dogs barking idiotically through endless nights. It is so bad that a sort of grandeur creeps into it." - H.L. Mencken on Warren Harding