Here we go again. This time I ran out to the garage, opened a few boxes and pulled out a few manuals from my instructor days, specifically: FM 23-65 Browning Machine Gun Caliber .50 HB, M2 -- since my memory of events 10 years in the past is obviously open to error.
I clearly remember engaging targets at 800m with a loose mounted, open iron-sighted single M2, usually mounted on the commander’s copula of an M-113. I don't recall any formal qualification (a la Tank Tables), however, I did find some good ole "Task, Conditions and Standards" for engaging popup targets on a formal machinegun range with the M2.
They include:
Task -- Engage multiple double E-type silhouettes at 400, 500 and 1,000 meters while wearing the protective mask (nice little handicap there!). Conditions -- blah blah 400, 500, 1000 protective mask bla blah... Standards -- gunner must impact one burst on each target within 45 seconds (while limited to 42 rounds)
or,
The same conditions using the AN/TVS- night sight (a handicap IMO)
or,
Gunner must impact one burst on the 1,000 meter target within 25 seconds (with only 14 rounds total to work with, leaving only two ranging bursts, perhaps three)
or,
As far as aerial engagements (with that handlebar deal I never saw in use) -- Superelevation (compensation made for the pull of gravity on the projectile) is another consideration for some weapons, but the caliber .50 MG projectile is basically flat out to 800 meters. Therefore, the gunner does not have to worry about it.
Now is a pintle mounted M2 different from 6 .50s hard mounted and zeroed in a fighter plane with an optical sight that helps in range estimation? Yes, and not in a positive way IMO in areas ranging from the sight picture to vibrations and limited ammo requirements for qualification. Were the targets moving? Well, no... but then they are providing about as much relative movement as most sky jousters or runners who fly the wings level, steady extension. Again, IMO the infrequent (and hardly game impacting) but noticeable hits at 1,000 plus meters are due to lazy extensions and experienced virtual gunners. Set convergence to a historical 400m max limit and these "issues" would evaporate entirely. Again, IMO.
Charon
BTW: on a personal note, the ATT broadband techs will be out to check the wiring setup in my new house tomorrow, so I may actually be able to fly more than 10 minutes without a "host connection lost" message popping up.

First time since the New Year (please let it be solved!) Hope to see more of you all soon in the unfriendly skies.