What I am talking about is point blank range.
Unfortunately it is generally believed that point blank range means pushing your pistol muzzle into the face of the target and pulling the trigger without needing to aim... ie it has come to mean shooting from so close you can't miss and therefore have no need to aim properly.
In actual fact that is the correct meaning except it refers to bullet trajectory.
The point blank range for the AK bullet is about 320m or something which means if you zero the rifle to that range and aim centre of target at no distance from the muzzle out to 320m will the bullet miss the target by going over their head.
If you zeroed your AK and set the iron sight to 1,000m you will be firing up into the air to lob the round up so that when it slows down and falls by the time it has travelled 1,000m it will fall back down to hit the target. The point is that at 200m away from the rifle the bullet might be 10 or 15 metres up in the air so you will only be killing someone in your line of sight perhaps between 950m and 1,020m.
Using the trajectory of the round you can zero the rifle and set the iron sights to 300m and therefore any human standing target that appears between 0m and about 350m you can place the front iron sight on their centre chest and get a hit somewhere on them without thinking how far away they are or adjusting the sights or doing any calculations... once you hit them with a round you can follow up with more hits to ensure the kill and then move on to the next target.
With the smaller lighter 5.45mm round the point blank range is about 450m or so which means targets within about 450m should be hittable with a 400m iron sight setting without adjustment or calculation.
From memory, the killing range of the AK-74 (the point at which the bullet technically still has enough energy to kill) is something like 1350m, although the effective range is a lot lower.
The energy of a bullet can be calculated quite accurately and drops off at a known rate, but accuracy generally falls off much faster and is much more critical in getting a kill...
A .22 calibre pistol bullet can kill when directed through the brain, while a 50 cal can remove your fingertip but otherwise leave you unharmed... unless you happened to be picking your nose at the time of course...
Officially the effective range of the 223 bullet from an M4 rifle or an FN Minimi with the short commando barrel they liked to use in Afghanistan was 200m.
Their other 223 calibre rifles were not much better despite longer barrel lengths.
They decided that a larger calibre rifle was needed in each platoon... you know... like the Soviets put SVD rifles in platoons over 60 years ago did...
Also after decades of criticising the Hind for moving all the time... often claiming because it was underpowered and couldn't hover properly, they now instruct their Apache crews to fly around more because a hovering helicopter is horribly vulnerable... even an RPG-7 will take it out and hovering behind a tree wont protect you from machine gun fire going through the branches...