Ballistics and Zeroing

Definition:Everything that happens to the projectile from the time the primer is struck by the firing pin until the projectile comes to a complete stop.

There are three ballistic phases:1. Internal2. External3. Terminal

Ballistics

Of the three phases, we will discuss one; External ballistics.A. Gravity and air resistance have a constant and continuous effect on a

bullet passing through the air.B. This constant effect causes the flight (trajectory) of the bullet to be a

definitive and uniform arc.C. A common cylindrical bullet has no loft capabilities, as does an airplane

wing.D. The sole purpose of the spin that is imparted upon a bullet is to keep the

projectile from tumbling end over end.E. A bullet fired from a true horizontal barrel begins to slow down and fall

towards the earth immediately upon leaving the muzzle of the weapon.

Two basic concepts that are common to most of us will help you to visualize how a bullet is sent through the air when leaving a rifle barrel.

A.The flight of a football. B.A common children’s top.

Bullet TrajectoryA bullet flying through the air is acted upon

primarily by two forces, which change the direction and velocity of its motion.

These two forces are:A. Gravity

-Causes the bullet to fall towards the earthB. Air Resistance

-Causes the bullet to slow down-Causes the bullet to fly erratically and tumble

Bullet Trajectory cont. We try and counter these forces on the bullet in three basic manners.• (1) Increase the angle of departure (elevating the muzzle) to counter the effects of gravity and allow the bullet to reach further distances.• (2) Impart spin and (3) high velocities on the bullet to counter air resistance and allow the bullet to fly in an nose forward manner at far distances.

Parts of a TrajectoryLine of Sight:This is what the shooter sees behind the sights and can be illustrated by drawing an imaginary line from your eye through the rear and front sights out to infinity. This is how you aim.

Line of Sight

Line of BoreThis is an imaginary line that is drawn from the chamber where the bullet lies through the barrel out to infinity. It is also the path a bullet would take if gravity and wind resistance weren’t a factor. It would in effect be a laser.

Line of Bore

Path of Bullet

Trajectory or Path of BulletThe path of flight that the bullet will take when it is fired from the rifle. The following is an example of what happens when a bullet leaves the bore of a rifle in which the barrel is horizontal to the ground and the line of sight is parallel to the line of bore.

Path of Bullet300m

300mPath of Bullet

What has to change to be able to engage this target?

•Increasing the angle of departure will allow the bullet to impact the target at the given distance.

•This causes us to lose sight of the target.•To be able to aim at the target, the sights must be adjusted.

Lowering the front sight post

Parallel Sight and Bore relationship

Re-acquire proper SIGHT ALIGNMENTand you have elevated the line of departure.

Parallel Sight and Bore relationship

Raise the rear sight

Re-acquire proper SIGHT ALIGNMENT,and you have elevated the line of departure.

25 meters 150 meters 300 meters

Line of Bore

Line of Sight

The diagram below shows us how the Army is able to zero at 25m and still be center of mass on a 300m target.

The distance the muzzle is raised may not be noticeable with the naked eye, but even at 25m, the muzzle is slightly elevated.

Minute of Angle (MOA)

100 200 300

1 moa

Unit of measure 1 minute of angle= 1 inch per 100 yards Sights and scopes move in Minutes of Angle Wind is estimated in Minutes of Angle

4”

2”1”

3”

400

Minute of Angle (MOA) worksheet

1) 6” @ 600m= ?MOA

2) 3 MOA @ 200m= ?inch

3) 6” @ 400m= ?MOA

4) 4 MOA @300m= ?inch

5) 20” @ 500m= ?MOA

6) 5 MOA @ 300m= ?inch

6”/ (6)00m=1 MOA

3 x (2)00= 6 inches

6”/4= 1.5 MOA

4 x (3)00= 12 inches

20”/ 5= 4 MOA

5 x 3= 15 inches

Value of clicks in MOA for iron sights:

WEAPON TYPE

ELEVATIONKNOB

WINGDAGE KNOB

FRONT SIGHT POST

M16A2 1 1/2 1 1/4

M16A4 1/2 1/2 1 1/4

M4 1 1/4 3/4 1 1/2

40”

19”

300m1. Elevation adjustment?

a. Need to come down 12”b. 12”/3(00)m= 4= 4 MOAc. 1 click on front sight= 1 ¼ MOAd. 4 MOA= about 3 clicks on front sight

2. Windage adjustment?IMPACT

a. Need to come left 21”b. 21”/3(00)m= 7 MOAc. 1 click of windage= ½ MOAd. 7 MOA = 14 clicks of windage

Zeroing: What is the definition?The average answer is: “Adjusting the sights so that the bullets impact where we are aiming.”

FM 3-22.9 states: The purpose of battlesight zeroing is to align the sights with the weapon’s barrel given standard issue ammunition.

Both answers are correct.

The Army has developed methods for engaging targets based on the following two scenarios:

1)Unknown distance=Battle Sight Zero (BSZ)

1)Known distance=Bullet Drop Compensating (BDC)

Zeroing continued

Battle Sight Zero

A Battle Sight Zero allows you to aim center mass on a target and achieve a hit from zero to 300m. A correctly zeroed rifle will impact within 10 inches of your point of aim.

10 inches32m 150m 300mLine of Sight

Trajectory

10 inches300m 400m350mLine of Sight

Trajectory

Battle Sight Zero

350m = 10” below point of aim 400m = 20 inches below point of aim

Bullet Drop Compensating

The elevation wheel on the rear sight is known as a Bullet Drop Compensator.The numbers on the wheel represent distances in meters. How it works:

Bottom out the rear sight and click up to 8/3 or 6/3. The BDC is now set for 300 meters.

Clicking up to 4,5,6,7 or 8 adjusts the trajectory of the round to engage targets at the corresponding distance (i.e. 4=400m, 5=500m).

One full revolution up from 300 correlates to the number on the left side of 3. For a 6/3 BDC the elevation would be set at 600 meters. This is why it is essential that the elevation wheel is bottomed out and then clicked up to 6/3 or 8/3 before zeroing.

Elevation changes at 25 meters are made with the front sight post so that the Bullet Drop Compensator can be used to engage targets beyond 300 meters.

Sight is bottomed out thereforethe right number is used (3), which indicates 300 meters.

Gap is noticeable, the sight is up one “revolution” from (3) so the left number is used (6), which now indicates 600 meters.

M16A2/A3Up 1 click

M16A4Up 2 clicks

7”-10”25 m

Representation of M16 Bullet Path

150m 300m 350m

ZEROING AT 25 METERS

M16 Rear Sights

The difference can be seen in the thread pitch between a rear sight on a fixed carrying handle and that of a detachable. This is why you have to come up only one click on the M16A2/A3 and two clicks on the M16A4. (Reference Army TM9-1005-319-10 Pg. 0011 00-7 #4)

M16A2/A3 M16A4

Difference in Thread Pitch

Representation of M4 Bullet Path

25m 150m 300m 350m

M4 Zeroing:The M4 and M16A4 share the same carrying handle, however the M4’s shorter barrel produces less muzzle velocity. The line of sight and path of the bullet cross at 25m AND at 300m.

Pre-range departure/post weapons draw checks

BDC is bottomed out and on300 meter setting

Small rear sight aperture is up and “windage” index lines are centered.

Front sight post is not bent ordamaged and the base of the sight post is flush with the front sight base.

Center MassIncluding head

Center MassNOT Including the head

Which is CENTER MASS?

Modified zeroing target

Emphasize zeroing in the lower half of the 4 cm circle. This will ensure a higher probability of hits from 150-250 meters.

3 Shot vs 5 Shot

If possible, 5 shot groups are recommended

Makes triangulation more accurate

INTRODUCTION TO THE TA01NSN ACOG

NSN 1240-01-412-6608

CHARACTERISTICS of TA01NSN 4x magnification. 32mm objective lens. Waterproof to depth of 66 feet. Eye relief 1.5 inches. Field of view at 100 yds. = 36.8 feet Adjustments= 1/3 MOA per click (clicks/in @

100 m.) = 3

ZEROING the TA01NSNTwo methods:1. 100 meter zero (most accurate)

- Use center cross hair- Point of aim/ point of impact

2. 25 meter combat zero- Use 300m reticle- Point of aim/ point of impact

Reticle/silhouette relationship @ 100 meters

200m 300m

100m

INTRODUCTION TO THE TA31F ACOG SCOPE

NSN 1240-01-514-8428

CHARACTERISTICS OF TA31F 4x magnification. 32mm objective lens. Waterproof to depth of 66 feet. Eye relief 1.5 inches. Field of view at 100 yds. = 36.8 feet Adjustment= 1/3 MOA per click(3 clicks = 1

inch @ 100m)

100m

300m

200mAiming points for:

For rapid engagement of targets less than 300m use this hold

ZEROING the TA31FTwo methods:1. 100 meter zero (most accurate)

- Use point of red chevron- Point of aim/ point of impact

2. 25 meter combat zero- Use top of 300m post (underneath chevron)- Point of aim/ point of impact

100 meter POA/POI

3 clicks = 1 MOAFor both elevation and windage

ZEROING the TA31F cont.

25 meter- POA/POIUse top of 300m post

9 clicks = 1”For both elevation and windage

12 clicks = 1”For both elevation and windage

ZEROING the TA31F cont.

If red chevron is too bright- cover fiber optic with tape.

What are your questions?