Well good day everyone, today we’ll discuss how to battle-sight zero your M16 or M4 carbine rifles. In order for the rifleman to develop skills that enable them to become combat effective. It is essential for the shooter to know how to zero their service rifle. Zeroing is the adjusting of the elevation and windage on the service rifle to cause the shots to impact where the shooter aims.
Zeroing compensates for the effects of weather and other external influences upon where the bullet impacts.
Point of Aim Point of Impact
To accurately engage targets, the strike of the bullet must coincide with the aiming point (Point of aim/point of impact) on the target. This must be done while compensating for the effects of weather and the range to the target. This is accomplished by adjusting the sights on your rifle to achieve point of aim/point of impact.
This process is called zeroing and it is the basic and most critical element of accurate target engagement. Along with a solid understanding of marksmanship fundamentals. One can’t work with out the other to place a shot or shot group in the center of the target at any given distance.
Elements of Zeroing
In order for shooters to understand the zeroing process there are particular elements that must be accounted for.
Line of Sight: Line of sight is a straight-line beginning at the center of the eye. It passes through the center of the rear sight aperture. It continues across the tip of the front sight post to the exact point of aim on the target.
Aiming Point: The aiming point is the precise point where the tip of the front sight post is placed in relation to the target.
Centerline of the Bore: Centerline of the bore is an imaginary straight-line beginning at the chamber end of the barrel. It proceeds out of the muzzle and continues indefinitely.
Trajectory: A bullet does not follow a straight line to the target. Instead, a bullet travels in a curved path, or arc, which is called the bullet trajectory.
Earths Gravity: This trajectory occurs because of the earth’s gravity, which pulls the bullet down toward the ground as soon as the bullet leaves the rifle’s barrel. The rate of this curvature increases as the bullet’s speed decreases.
Compensating for Gravity: To compensate for this affect (so that the bullet will impact the target), the muzzle of the rifle must be elevated. This is accomplished by applying elevation to the rifle sights. The greater the distance to the target, the higher the bullet’s trajectory must be to impact with the target. Therefore, the greater the distance to the target, the greater the elevation that must be applied to the sights to engage the target from that distance.
Types of Zeroes:
Battlesight Zero (BZO): A BZO is the elevation and windage settings required to place a single shot, or the center of a shot group, in the center of a target at 300 yards under ideal weather conditions.
A BZO is the sight settings placed on your rifle for combat, in combat, your rifle’s BZO setting will enable engagement of point targets from 0 – 300 yards in no wind condition. 8/3 is the rear sight elevation setting for the M-16 BZO. 6/3 is the rear sight elevation knob setting for the M-16 & M-4 Carbine.
Zero: A zero is the elevation and windage settings required to place a single shot, or the center of a shot group, in center of the target at a specific range, from a specific firing position, under specific weather conditions.
True Zero: A true zero is the elevation and windage settings required to place a single shot, or the center of a shot group, in the center of a target at a specific range other than 300 yards. This is also from a specific firing position, under ideal weather conditions.
Sighting System:
The sighting system of the service carbine consists of a front sight post, a rear sight aperture with windage knob, and a rear sight elevation knob. Moving each of these sights one graduation or notch is referred to as moving one “click” on the sight system.
Front Sight: The front sight consists of a square, rotating sight post with a four-position, spring-loaded detent. The front sight post is moved up or down when zeroing the rifle for elevation. Depress the detent and rotate the post to adjust for elevation up or down.
Moving Front Sight Post: To raise the strike of the bullet, rotate the post clockwise (in the direction of the arrow marked UP) or to the right. When rotated clockwise, the front sight post moves down into the front sight housing. It causes the shooter to raise the weapon’s muzzle weapon to realign the tip of the front sight post in the center of the rear sight aperture. To lower the strike of the bullet, rotate the post counterclockwise or to the left. When rotated counterclockwise, the front sight post moves up and out of the front sight housing. It causes the shooter to lower the weapon’s muzzle to realign the front sight post tip in the rear sight aperture’s center.
Rear Sight: The rear sight consists of two sights. Rear sight elevation knob, and a rear sight windage knob.
Rear Sight Elevation: The rear sight elevation knob is used to move the strike of the round up or down, and to adjust for elevation or range to the target. The knob has an index on the left side which indicates the settings for a specific range to target. To adjust for elevation or range rotate the knob so the desired setting is aligned with the index on the left side of the receiver. Each number on the knob represents a distance from the target in 100 yard increments.
Rear Sight Windage: The rear sight windage knob is used to move the strike of the round left or right. To move the strike of the round right, rotate the knob clockwise (in the direction of the arrow). To move the strike of the round left, rotate the knob counterclockwise.
Rear Sight Aperture: The rear sight aperture consists of two separate sights. One aperture is for normal range and the other aperture is for short range limited visibility engagement.
The normal range aperture is unmarked and is used for zeroing and in most firing situations. The limited visibility aperture is the larger aperture. It may be used for engagement of targets closer than 200 yards, and target engagement during limited visibility, or when a greater field of view is desired.
Zeroing carbine rifle:
Zeroing at 300 yards: Zeroing is conducted at a range of 300 yards. The rifle’s sights must be adjusted so the bullet’s trajectory and line of sight intersect at a range of 300 yards. Zeroing at 300 yards accomplishes this.
Establishing Initial Sight Settings: To begin the zeroing process the rifle sights are placed on a known BZO previously established or on initial sight settings.
Front Sight Post: To set the front sight post to initial sight setting, depress the front sight detent and rotate the front sight post until the base of the front sight post is flush with the front sight housing.
Rear Sight Elevation Knob:
M-16: Rotate the rear sight elevation knob counterclockwise until the rear sight assembly is bottomed out. Rotate the rear sight elevation knob clockwise until the number 8/3 aligns with the index mark located on the left side of the upper receiver.
M-16 & M4 Carbine: Rotate the rear sight elevation knob counterclockwise until the rear sight assembly is bottomed out. Rotate the rear sight elevation knob clockwise until the number 6/3 aligns with the index mark located on the left side of the upper receiver.
Windage Knob: To set the windage knob to initial sight setting, rotate the windage knob until the index line located on the top of the large rear sight aperture aligns with the centerline on the windage index scale located on the moveable base of the rear sight assembly.
Proper steps to Zeroing Rifle:
Fire 3 Round Shot Group: When the target appears shooters will fire a well aimed 3 round shot group in a time limit of one minute.
Mark the Target: The target will be lowered to the pits and marked indicating shooters 3-shot group.
Plot the Group: When the target is raised from the pits, ensure shooters plot the 3-shot group.
Triangulate the Shot Group: Triangulate shooters shot group by drawing a line to form a triangle connecting all 3 shots. Locate the center of the triangle and make elevation and windage adjustment recommendations to shooters.
Fire 2nd 3 Shot Group: When the target appears shooters will fire a 3-shot group in a time limit of one minute.
Mark the Target: The target will be lowered to the pits and marked indicating shooters 3-shot group.
Plot the Group: When the target is raised from the pits, ensure shooters plot the 3-shot group.
Triangulate the Shot Group: Triangulate your shooters shot group by drawing a line to form a triangle connecting all 3 shots. Locate the center of the triangle and make elevation and windage adjustment recommendations to shooters.
Fire 4 Shot Group: When the target appears shooters will fire a well aimed 4-shot group in a time limit of one minute. This last group is to confirm the sight adjustments that were made.
Final Steps: Once shooters have confirmed their adjustments and have their sight settings, there needs to be an adjustment determined for wind (if present) and taken off the sight settings. This setting becomes the zero setting for the rifle, and must be recorded in your shooters data books.
These are the proper steps in order to BZO your rifle. Any questions please feel free to contact me.
Isaac J. Hall II
#SemperKill
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