The 5.56 X 45

Any veteran that was trained on a M16 (1962) , M4(present) or any variant between knows max kill is 300 meters.

Any thing further is wounding/maming which would take other soldiers out as they should help the wounded .
That was the theory anyway.

Got to give ‘Free North Carolina’ a big Oooo Raaahh on that article. A great supporting article for this was the Popular Mechanics article from June_july 1967, when the M16 was just entering into use for VietNam. They did a BIG layout, talked to old Stoner himself (man who designed the M16), and discussed a LOT of things that over the decades, have dropped off the radar when talking assault rifles. Things like why the Army considered the rifle, why Stoner considered the caliber when designing the rifle, etc.

Basically, to ‘short-story’ it, Stoner couldn’t afford to license the new Winchester .243 caliber (which he wanted first) to the rifle, as Winchester still had protection on the new caliber design, but when Remington heard this, they quickly threw their old ‘no longer protected .223 caliber at Stoner and begged him to use it instead (Winchester saw the .243 as a new premium smaller large-game cartridge, while Remington was glad to give away the .223 just to get movement on sales, and saw what the military tie-in could mean to them).

The first AR/M-16′s jammed terribly, so in came the forward bolt assist feature. They were temperamental and did not like water or grit (and still don’t, to this day). The advantage, that really sold them to the military, was the weapon’s weight, and the fact that a soldier could carry 200-rounds of 5.56 for the weight of only 90-rounds of 7.62 (the old .308 Winchester that the M-14 was chambered on). In the end, weight savings per round sold the rifle to high ranking admin clerks at the pentagon that never tried to shoot a man-sized object with what was, in fact, a small animal varmint round. The rest is history.

The round is super-fast, flat shooting, but is defeated by low projectile weights that loose power rapidly when velocity drops. It is, after all, just a matter of physics.

Compared to a 168-grain 7.62 cartridge, the 5.56 can’t compare. The 7.62 retains mass and excels at downrange force. This is why Kalishnikov designed the AK-47 around the 7.62 cartridge, while Stoner simply had a general idea of cartridge and designed the rifle first. Even Stoner when asked, said he would rather carry an AK into battle, while Kalishnikov said he didn’t trust the AR in battle.

In battle, an AK wears out, while an AR catastrophically and suddenly fails.

AR-15/M16, the best coyote and prairie-dog gun you could dream of. The worst Mattel toy you could ask for in combat (Mattel owned the AR design for a period of time at the end of the 20th century).

Forget the AR, stick with ANYTHING that fires 7.62 (my personal favorite is the Springfield Armory M1A).