I guarantee that shooter was still surprised he hit the target. No matter how many calcs you do for that distance, there is a huge luck factor involved. I think with modern sniper rifles and optics it will still be tough to get a first rd hit at 1500 yds. The 50 bmg is really not the ideal long range sniping tool, although there have been some impressive hits. Like anything, you hear about the hits and not so much all of the misses that almost certainly precluded those shots. The inconsistency in ammo alone, with all else being perfect, would probably account for variations of 10-20 ft at those distances, and that's with high precision hand loads. I don't call bs on the shot. I'm sure he made it. But I would bet on a good day that same shooter would probably miss 19/20 shots at that range. You are hearing about the one that he hit. It's next to impossible to make a "reliable" hit at that range.