What Zero For Your Fighting Rifle?
One of the many myths and legends that abound promulgates the thought that many rifle fights take place at long range. Conceptually this sounds good and we all like it because it satisfies our ego to shoot and hit targets at long range. In reality many rifle fights may fall well within ranges normally considered to be handgun distances.
Whatever the range, marksmanship is always a helpful problem solver and hitting the target is the intent. However hitting the target may be harder than you think. Thinking logically, if every center fire round ever fired in anger had hit its intended target there would be no air breathing entities left on the planet. Lots of angry rounds have been fired and lots of targets have been missed.
As one example, the 8th United States Army Air Force in World War II fired a nominal 76.9 million rounds of .50 caliber and .7 million rounds of .30 caliber machine gun ammunition downing 6,090 enemy aircraft which equates to about 12,700 rounds fired per enemy aircraft. Although rifles are not machineguns mounted in aircraft you get the point.
The Instruction
To help us hit the target with each rifle class I teach, the first range exercise is to check on or confirm the zero of the rifle being used. The vast majority of the rifles used here are of military origin so the issue of mechanical off set or the difference between the height of the sight and the center axis of the bore comes into play. If we were dealing with a scoped rifle, this offset would be called parallax.
But to set the record straight, the true issue is not whether optical sights or iron sights are used. In fact, simply dealing with the offset is the issue. Many times at extended ranges, the offset is not an issue as the projectile trajectory arc generally passes from below the line of sight through the line of sight and then re-crosses at an extended range.
This projectile cross and re-crossing is determined by range, velocity, wind and other elements that affect the projectile. Two other important factors to be aware of are POA vs. POI. Point Of Aim is where the sights are located on the target when the hammer falls. Point Of Impact is the point on the target where the projectile strikes. Remember, point of aim and point of impact are not and may not be the same based on zero and range to target, among other things.
The Zero
The zero or cold zero as called by some, is where the first projectile strikes on the target from a cold clean barrel. Cold zeros may print different than a string of five rapid shots but it’s not always necessarily so and may vary from rifle to rifle.
Many students here at school are either law enforcement officers or rifle-armed civilians who want to assure a surgical placement of projectiles on target. So in that vein the zero or the quality or type of zero they have effects their ability to deliver that surgical hit on target. Many law enforcement officers working in cities or built up areas seem to elect a POA/POI zero at 25 yards. The next most popular range seems to be 100 yards for the denizens of the city. Rural residents often go with a military type battle zero.
The actual zero may not be as important as the ability to know if your rifle is zeroed and where your zero places projectiles on targets at different ranges.
Using an AR15 type rifle with a nominal 2 1⁄2-inch sight to muzzle offset, we established the impact point above or below the POA with varying initial zeros. The chart tells the tale, and may help you to better choose which zero is appropriate for the environment you work in.
Remember the offset in application — just because the sight is clear does not mean the muzzle is clear of obstructions in front of the barrel. Clear sights do not mean a clear path for your projectile.
Also of interest is the fact that inside 15 yards, no matter what zero you have, the offset will prevail, and the shooter will have to hold the POA off to have the POI strike where they wish.
Since hitting the target is, in fact, the desired result, it would then make sense to zero our rifle to know where the projectiles will strike the target. By knowing what a zero is, having one and knowing how to use it, we will go a long way towards solving any marksmanship problems we may encounter.
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