I can remember things from 35 years ago clear as a bell, but I struggle to remember what I had for lunch yesterday.

Anyway, here are some numbers:
From a front firing .50 caliber MG:
@ sea level, no hits at all after 1,050 yards
@ 11,000' MSL, you can get a few "golden BB's" hits (one round per 1,000 rounds fired) at about 1,189 yards.
From a rear firing gun:
@ 6,000' MSL, "golden BB's" only at 1,324 yards.
@ 11,000' MSL, "golden BB's" only at 1,350 yards.