Comment by jakub_h

.50 BMG is supersonic but drops in velocity rather quickly, like any other small caliber round. Depending on the position of the shooter (especially if opposite to the recording equipment relative to the LV, for example), chances are that the cameras with mikes recording the LV might have problems hearing it. I'm not sure at what distance it drops into subsonic region but the size of the target should allow for some pretty large distance. Powder load could also be tweaked. One has to assume a shooter with significant resources if a deliberate action against a multiple-$100M target is the premise.