I'd add that .50 BMG is more precisely a "material destruction" round (aircraft being "material"), it's rather excessive for a human target except at very long

I'd add that .50 BMG is more precisely a "material destruction" round (aircraft being "material"), it's rather excessive for a human target except at very long ranges as pioneered by e.g. Carlos Hathcock in Vietnam (a serious "competitor" to Chris Kyle modulo the very different terrain etc.). I've read that the Barrett M82 has been used a lot in explosive ordinance disposal, something for which a single aimed shot (at a very long distance) is ideal, whereas a full auto M2 would be gross overkill, not to mention not particularity man portable (30 pounds, a bit over the weight of our medium general purpose machine gun (but that also requires spare barrels and a lot of ammo), vs. 128 pounds with tripod).