What distance should you zero the sights or optic on your AR-15 style rifle? For the flattest, set-it-and-forget-it trajectory, zero your red dot, holographic, and backup sights at 50 yards. Trust us, or keep reading to find out why.
This page does not address A2 style sights found AR-15 style rifles with fixed and removable carry handles. For detail instructions on how to zero A2 sights check out Savannah Arsenal’s How To Zero AR-15 A2 Sights.
For ballistic calculations used throughout this page I used the following ammunition and velocities. Your results may vary slightly.
- 20″ barrel / M855 62-grain FMJ — 3061 FPS
- 20″ barrel / M193 55-grain FMJ — 3254 FPS
- 16″ barrel / M855 62-grain FMJ — 2938 FPS
- 16″ barrel / M193 55-grain FMJ — 3075 FPS
- 14.5″ barrel / M855 62-grain FMJ — 2861 FPS
Battle Sight Zero = Set It And-Forget It:
Simply defined, “Battle Sight Zero” (sometimes referred to as “Battle Zero”, “BSZ”, or “BZ”) is a theoretical “set it and forget it” setting for your backup sights or non-magnified optics that will allow your to make combat effective hits out to a certain distance without applying any hold-over or hold-under from your point-of-aim. With your sights set to a “Battle Sight Zero” you will know that your rounds will hit no more than “X” inches above or below your point-of-aim from CQB distances out to “Y” yards or meters distance. You will want your sights set at a distance that will provide the flattest trajectory, and thus the least deviation in point-of-aim and point-of-impact at varying distances. Fortunately for those using .223 Remington / 5.56mm NATO rifles, there is a distance that you can zero your rifle and enjoy a very flat trajectory out past 200 yards away.
What Zero Distance Provides The Flattest Trajectory?:
It is important to zero the elevation of the sights with a single setting that will take the most advantage of the flat shooting trajectory of the 5.56mm/.223 caliber rifle round. The following diagram compares the trajectories of bullets when zeroed at 25, 50, and 100 yards. While you can expect minor variations in trajectory depending on if you are using a carbine with a 16″ barrel or a full-size battle rifle with a 20″ barrel, as we as with different brands, loads, and weights of ammunition, the data supplied is accurate enough to compare trajectories for use with backup sights and non-magnified optics.
100 Yard Trajectory:
The first chart shows the trajectory of a 5.56mm NATO round when fired from an AR15 style rifle. The dash line represents the shooters point of aim. The bullet departs the barrel approximately 2.5″ below the point of aim. It’s flight path reaches the shooters aiming point at 100 yards (point-of-aim (POA) = point-of-impact (POI). The bullet then drops back down to 2.5″ below POA at 200 yards, and plummets drastically after that. This isn’t a terrible zero if you never plan on shooting past 200 yards as the bullet will impact somewhere within the distance of the barrel to the top of the rifle’s sight base. Not terrible, but you can do better.
25 / 300 Meter Trajectory:
The next graph represents the traditional military method of zeroing the rifle at 25 / 300 meters (meaning that you zero the rifle at 25 meters and can expect a second POA = POI at 300 meters). This was traditionally done with adjustable rear sights, such as those found on rifle’s equipped with carry handles, set on the 300 meter setting, but the target set 25 meters away. This is a TERRIBLE zero setting. At 100 meters (109 yards) the your rounds will impact over 4″ above your POA. At 175 meters the bullet impact will reach its peak apogy at roughly 6″ above your POA. The USMC has finally accepted that this isn’t the most efficient way to zero an AR15 / M16 style rifle. Do not use a 25 meter “set-it-and-forget-it” zero.
50 Yard Zero:
The next graph illustrates the ballistic trajectory of a 5.56mm NATO round with a 50 yard zero (not meters). This zero is commonly referred to as “Improved Battle Sight Zero”. As with the graphs above, you can see that the bullet leaves the rifle 2.5″ below the point-of-aim (POA). The bullets trajectory will pass through the shooters point-of-aim at 50 yards. At 100 yards it impact approximately 1.5″ high. It will reach its peak apogy of 1.8″ at approximately 140 yards. Around 220 yards the round will again pass through the shooters (POA). At 250 yards the round will impact approximately 2.5″ below POA. This data shows that on its flight from the rifle’s muzzle out to 250 yards, the bullet will hit somewhere within plus or minus the height of the rifles front sight base (+/- 2.5″). That’s pretty darn flat.
50 Yard, 25 / 300 Meters / 100 Yards Trajectory Comparison:
The final graph compares all three trajectories. The 100 yard zero isn’t terrible, but you can do better. The 25 / 300 meter zero is terrible. The 50 yard zero will provide the combat shooter with the flattest trajectory out to approximately 250 yards, and is the recommended distance to zero your backup sights and non-magnified optics as a “set it and forget it” Battle Sight Zero setting.
The 50 yard zero provides the flattest trajectory for the AR-15 style rifle. It is easy to see why the 50 yard zero is the best choice, and how your point-of-impact will never be more than +/- 2.5 inches from your point-of-aim, from close up and personal “bad breath” distance, all the way out to a distance of approximately 250 yards. Competitive shooters and the USMC now realize this and employ the 50 yard zero technique with backup sights and non-magnified red-dot and holographic optics.
Important: This Battle Sight Zero is for AR-15 style rifles firing 5.56mm NATO ammunition. It is not necessarily an appropriate Battle Sight Zero for other 5.56mm rifles (because they may have sights of different height over bore than the AR-15), or rifles in other calibers. This is not the correct zero for Tavor, Steyr AUG, or AK rifles chambered in 5.56mm.
Backup “Iron” Sights With Your Red-Dot Optic:
BUIS is an acronym for “backup iron sights”. This is nothing more than a catchy label for backup sights that you can use when and if your primary electronic or magnified optic is damaged or fails. “Iron” simply refers to their metal parts to differentiate them from electronic optics, although none of them are made from iron, but rather aluminum, steel, and plastic. Backup sights can simply be a rear sight that sits on a flat-top receiver behind the optic, or it may be a set of both front and rear sights for an ORC (Optic Ready Carbine: a carbine with only rails on top and no front sight base that is ready for customization by the end user).
Most rear backup sights are only capable of windage adjustments. Elevation must be established with adjustments to the front sight. Most backup sights do not have the fine adjustments like those on a carry handle. Zero them as close as possible, but don’t expect perfection. Zero your backup sights for point-of-aim / point-of-impact at 50 yards. Be sure to use Loctite thread locker when mounting your backup sights. I promise that the screws will eventually loosen during shooting and the sights will lose their zero.
If you run some type of aiming device (holographic sight, red-dot sight, or magnified optic) on your rifle then you need to have a backup sight(s) on your rifle. Murphy’s Law dictates that your electronic optics will break or be damage, your scopes will break or fog up, and your batteries will go dead at the worst time. If this happens and you don’t have a backup system for aiming, then that weapon is out of the fight. You soon will be too.
If you are going to use BUIS to backup your optic as they are intended, then keep them folded down and out of the way until the optic fails or is damaged. Then simply pop them up into position and use them while looking through the dead optic. If the optic is too damaged to look through, then if you have equipped it with a quick release mount and can remove it out of the way so that you can continue the fight with the backup sights.
BUIS Zeroing Procedure:
Most backup type sights do not have as many fine, incremental adjustments as the RDS that they will backup. You won’t be able to adjust the backup sight as finely as you will the optic. The most efficient method is to finely zero your optic first, and then match your BUIS as close to the RDS as possible (don’t get upset if you can not get it to match perfectly). You will want to zero the RDS with the sights folded down and out of the way. Then you pop up your backup sights, and while looking through both the backup sights and the optic, adjust the sights so that the reticle (the red dot) of the RDS bisected across the middle by the top of the front sight post. With a properly zeroed RDS you can zero your BUIS without firing a shot. Simply match them to the RDS.
Unlike A2 sights, with most backup style sights you zero your elevation setting to your desired battle sights zero (BSZ) and leave it. Your elevation will be adjusted with the front sight, and windage will be adjusted with the rear sight.
BUIS Sight Adjustments:
When adjusting the sights on any firearm, remember the acronym, “FORS”. Front Opposite, Rear Same. For firearms that require you to move the front sight to adjust bullet impact, you will want to move your sight in the opposite direction that you want to move the shot group. If you have to adjust the rear sight, then you move it in the same direction that you want your bullet group to move.
With 99% of backup style sights, elevation is adjusted with the front sight post, and windage is adjusted with the rear sight.
Adjust Elevation On The Front BUIS:
Use the acronym, FORS. Front Opposite, Rear Same.
- To raise your next shot group, rotate the front sight post clockwise.
- To lower your next shot group, rotate the front sight post counterclockwise.
Adjust Windage On The Rear BUIS:
Again, use the acronym, FORS. Front Opposite, Rear Same.
- To move your next shot group to the left, turn the windage knob counterclockwise.
- To move your next shot group to the right, turn the windage knob clockwise.