This Classic from Tiger McKee explains the reasoning behind his preferred zero for the AR carbine – originally published February 2009.
There is a constant, ongoing debate about the distance at which the AR rifle should be zeroed. Ideally you need a zero that provides the least deviation between your POA (point of aim) and the actual POI (point of impact) of your bullet. From tests I have run it seems that the best distance to zero the AR for self-defense and law-enforcement purposes is 75 yards.
A 75 yard zero provides the least deviation between your POA and POI from 25 to 100 yards. At 25 yards the POI will be around 1.5 inches low, and at 100 yards POI is approximately 1.5 inches high. Of course, this depends on the offset between your sights and barrel, barrel twist and length, and ammo. So, for this discussion we’re talking about using iron sights, or a red-dot optic mounted on a flattop rifle.
There are some people using 25 yard zeroes, based on the fact that 25 yards and closer is where the majority of their shooting will take place, but this creates a couple of problems. First, even with a 25 yard zero, once you get 20 yards and closer you’ll still have to compensate for the offset between the sights and barrel because the POI will be 2-2.5 inches lower than your POA. With body shots this may not be an issue, but for headshots, especially in a hostage situation, it is critical. The second problem with a 25 yard zero is that if you do need to take a shot from extended distances your POI will be way off. For example, a shot from 100 yards with a 25 yard zero will have a POI around 6-9 inches high, again depending on weapon variables. Having to compensate for this much difference between POA and POI can be difficult, especially under stress.
What about if you are forced to make a shot from extended distances, say a shot from 200 yards? First, it will be rare that you would have to make a shot at that distance, especially in LE or self-defense work. Plus, the average drop of the .223 from 100 to 200 yards is roughly 3 inches, so with a 75 yard zero you’re still capable of hitting body shots by aiming center of mass.
The beauty of the rifle is the ability to place a single projectile exactly where you want it. So regardless of the distance at which you zero, learn the difference between POA and POI from 3 to 100 yards. Hit the range, work from actual fighting positions and different distances so you have the data necessary and develop the skills required to get that hit. When lives are at stake, you may not get a second chance.
— Tiger McKee
