Automatic fire is considered “area fire”, where you don’t home in on a particular target but blanket the killing zone with fire. In a military situation, troops are (if properly led) dispersed and know how to use cover, with some cover available. In this case, people were massed and there was no cover to speak of.
“Cover” is a term of art meaning something to get behind that has a good chance of protecting one from fire. “Concealment” is something that hides you but will not stop incoming. There was little concealment available, either.
400 yards is at the far end of the effective range of the AR and AK rifle ammo. Aimed fire with the AR is possible with a lot of practice, good optics and match ammo.
I reckon many of the injured were due to ricochets. Choice of ammunition could add to the potential for ricochets…steel cored military ammo that does not expand as it hits the first target but drills through.
The average hunting round is designed to penetrate a certain amount and then expand, hopefully to expend all its energy into the animal and achieve a quick, humane kill. Some designs work better than others and it depends on the animal. Such rounds used here would expand, lose energy as they hit a person. They may not exit the body. If they do and hit cement, they will further deform and lose energy, becoming less effective. I will be interested to see what the reports are.
Also, reports indicate the range of calibers as being from “.308 to .223” but only AR and AK rifles are noted. I wonder if there is confusion between a “.308” (7.62x51mm military) and the AK round (7.62x39mm), a much less powerful round. There are “AR configuration” rifles in 7.62×51 (such as the AR10 and others) so it’s possible this round was used. That may explain the numbers of killed. The 7.62×51 is still quite effective at 400 yards. It is widely used by police and military as a sniper round, though ranges more than 500 yards usually are dealt with by a .300 Winchester Magnum or .338 Lapua. The very long shots are made with .50 caliber BMG, a cartridge designed by John M. Browning before War One, and in continuous use since then in heavy machine guns on the ground, in the air and asea, and in sniper rifles for a couple of decades anyway.
by George Schirtzinger via Facebook