Over 1 mile - a .50, and no dispersion, no spray and so precise on target that it picks a selected person within a group of persons and with just one and the first round? Very hard to believe, I admit.
Even more, the cal .50 is the commander'S weapon that doe snot get operated by the gunner'S primary sights. He can give a more precise range by lasing the target of course, but still the TC needs to use the purely optical sight for the .50. Without magnification. Elevation done via handcranks, not by just pointing and swinging the weapon like a LMG on a tripod. And then just one shot? Heck, this is no sharpshooting rifle, this is no M107.
You can see auxiliary sight'S design from various vehicles (LAV, M2, M1, Leo1, Leo2) in this essay, scroll down the text a bit.
http://www.subsim.com/radioroom/showthread.php?t=191272
I check that with the eSim forums. Many tankers there, probably somebody there has heared the story if it is true. But I have a hard time that you even can use the tank'S main aiming devices to precisley pick a single person in a group of person at over 1 mile and avoid the dispersion, always hitting with just one round.