Ballistics and Zeroing * * * * * * This is the mechanical

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Ballistics and Zeroing
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Ballistics

• 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
• Internal
• External
• Terminal

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• Of the three phases, we will discuss one
• External ballistics.
• Gravity and air resistance have a constant and
  continuous effect on a bullet passing through the
  air.
• This constant effect causes the flight
  (trajectory) of the bullet to be a definitive and
  uniform arc.
• A common cylindrical bullet has no loft
  capabilities, as does an airplane wing.
• The sole purpose of the spin that is imparted
  upon a bullet is to keep the projectile from
  tumbling end over end.
• 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.

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• 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.
• The flight of a football.
• A common childrens top.

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• Bullet Trajectory
• A 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
• Gravity
• -Causes the bullet to fall towards the earth
• Air Resistance
• -Causes the bullet to slow down
• -Causes the bullet to fly erratically and tumble

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• 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.

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• Parts of a Trajectory
• Line 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.

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Line of Bore This 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 werent a factor. It would in effect
be a laser.
Line of Bore
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Trajectory or Path of Bullet The 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 Bullet
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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.

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Parallel Sight and Bore relationship
Lowering the front sight post
Re-acquire proper SIGHT ALIGNMENT and you have
elevated the line of departure.
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Parallel Sight and Bore relationship
Raise the rear sight
Re-acquire proper SIGHT ALIGNMENT, and you have
elevated the line of departure.
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The diagram below shows us how the Army is able
to zero at 25m and still be center of mass on a
300m target.
Line of Bore
Line of Sight
25 meters
150 meters
300 meters

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

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Minute of Angle (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

1 moa
100
200
300
400
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Minute of Angle (MOA) worksheet
6/ (6)00m1 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
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Value of clicks in MOA for iron sights
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• Elevation adjustment?

300m

• Need to come down 12
• 12/3(00)m 4 4 MOA
• 1 click on front sight 1 ¼ MOA
• 4 MOA about 3 clicks on front sight

IMPACT
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• Windage adjustment?

• Need to come left 21
• 21/3(00)m 7 MOA
• 1 click of windage ½ MOA
• 7 MOA 14 clicks of windage

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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 weapons
barrel given standard issue ammunition.
Both answers are correct.
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Zeroing continued

• The Army has developed methods for engaging
  targets based on the following two scenarios
• Unknown distanceBattle Sight Zero (BSZ)
• Known distanceBullet Drop Compensating (BDC)

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• 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.

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Battle Sight Zero

• 350m 10 below point of aim
• 400m 20 inches below point of aim

Trajectory
Line of Sight
300m
400m
350m
10 inches
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• 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. 4400m, 5500m).
• 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.

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Sight is bottomed out therefore the 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.
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Representation of M16 Bullet Path
150m
300m
350m
7-10
25 m
ZEROING AT 25 METERS
M16A2/A3 Up 1 click
M16A4 Up 2 clicks
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M16 Rear Sights
M16A4
M16A2/A3

• 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)

Difference in Thread Pitch
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Representation of M4 Bullet Path
150m
300m
350m
25m
M4 ZeroingThe M4 and M16A4 share the same
carrying handle, however the M4s shorter barrel
produces less muzzle velocity. The line of sight
and path of the bullet cross at 25m AND at 300m.
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Pre-range departure/post weapons draw checks
Small rear sight aperture is up and windage
index lines are centered.
BDC is bottomed out and on 300 meter setting
Front sight post is not bent or damaged and the
base of the sight post is flush with the front
sight base.
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Which is CENTER MASS?
Center Mass Including head
Center Mass NOT Including the head
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Modified zeroing target
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Emphasize zeroing in the lower half of the 4 cm
circle. This will ensure a higher probability
of hits from 150-250 meters.
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• If possible, 5 shot groups are recommended
• Makes triangulation more accurate

3 Shot vs 5 Shot
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INTRODUCTION TO THE TA01NSN ACOGNSN
1240-01-412-6608
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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 _at_ 100
  m.) 3

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ZEROING the TA01NSN

• Two methods
• 100 meter zero (most accurate)
• Use center cross hair
• Point of aim/ point of impact
• 25 meter combat zero
• Use 300m reticle
• Point of aim/ point of impact

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Reticle/silhouette relationship _at_ 100 meters
100m
200m
300m
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INTRODUCTION TO THE TA31F ACOG SCOPENSN
1240-01-514-8428
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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 _at_
  100m)

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100m
Aiming points for
200m
300m
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For rapid engagement of targets less than 300m
use this hold
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ZEROING the TA31F

• Two methods
• 100 meter zero (most accurate)
• - Use point of red chevron
• - Point of aim/ point of impact
• 25 meter combat zero
• - Use top of 300m post (underneath chevron)
• - Point of aim/ point of impact

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ZEROING the TA31F cont.
100 meter POA/POI
3 clicks 1 MOA For both elevation and windage
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ZEROING the TA31F cont.
25 meter- POA/POI Use top of 300m post
12 clicks 1 For both elevation and windage
9 clicks 1 For both elevation and windage
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If red chevron is too bright- cover fiber optic
with tape.
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What are your questions?