UNITED STATES MARINE CORPS WEAPONS TRAINING BATTALION

MARINE CORPS COMBAT DEVELOPMENT COMMAND QUANTICO, VIRGINIA 22134-5040

STUDENT OUTLINE

APPLIED WOUND BALLISTICS

1022LP

APPROVAL____________________________ DATE_______________

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1. INTERNAL BALLISTICS: Internal ballistics is the study of what a projectile is doing while it is inside the weapon:

a. The primer is crushed, sending a jet of flame into the powder contained within the cartridge case. The powder is ignited by the flame and begins to burn. As the powder burns, chamber pressure builds. The case expands from the heat and pressure, forming a gas-tight seal in the chamber. This is known as obturation. The projectile is pushed forward through the throat and engages the rifling. b. The powder in the cartridge continues to burn, adding pressure and increasing the velocity of the projectile. The bullet forms a gas-tight seal with the barrel, preventing escape of gasses around the projectile.

c. As the round travels down the barrel, it is being rotated by the rifling cut into the barrel. This rotation stabilizes the round once it exits the barrel. The stability of the round is determined by the twist rate, and is designed to give the optimal amount of stability to a given projectile. Longer, heavier rounds require more spin than lighter, shorter rounds for optimal performance. If the twist rate is wrong, it will adversely affect the round. If the round is over-stabilized, the projectile will perform poorly in tissue, as it will punch straight through with minimal disturbance of tissue. If the projectile is not stabilized enough, it will not travel accurately and will be heavily affected by atmospheric conditions and air drag. 2. EXTERNAL BALLISTICS: External ballistics is the study of what a projectile is doing while it is in flight: a. When the projectile exits the bore, velocity begins to drop, as there is no longer any force to speed up or maintain the speed of the round. Air drag immediately begins to effect the round, slowing it down. (1) As the projectile ends, it contacts with the lands and grooves of the barrel, the gas-tight seal that was behind the projectile is broken. The expanding gas behind the bullet exits along with the bullet, and is expelled around the bullet and bore. (2) The bullet will not be stable when it exits the bore due to lack of constriction provided by the barrel and by the exiting gasses. The bullet will wobble in flight (precession)

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until gyroscopic action stabilizes it. This initial wobble is known as the Magnus Moment. (3) It is the brief period in a bullets flight when it is not stabilized. Due to gyroscopic stabilization the bullet may not travel directly aligned with the path of flight. Instead, the bullet will rotate around its center of gravity. The optimal amount of twist for a 62-grain bullet (SS109 in M855) is one rotation in eight to nine inches (1/8, 1/9). The optimal amount of spin for the M856 tracer is 1/5 to 1/6. The reason for this is that the M856 is slightly longer and heavier than the M855. The best compromise for both trajectories to be about the same was a 1/7 twist for the service rifle. Although not optimal, it is acceptable. b. Precession: Precession is a circular motion of the bullets center of gravity aligning with the projectiles center of mass as the bullet is rotated and stabilized. Yaw is a back and forth wobbling of the round, and is essentially a two dimensional view of precession. Precession is present in any bullets flight; the degree and length are what makes a certain round more or less accurate than other rounds. Gyroscopic stabilization is intended to limit these motions by matching bullets to a given twist rate. These deviations will generally be no greater than a few degrees.

c. Even if the bullet is completely stabilized it will still have a slightly upward orientation during most situations since the bullet is not fired parallel to the sight plane. The round must travel up to meet the sight plane (Initial Point) then travels forward and up until it reaches the height of its travel (Maximum Ordinate), which will be at roughly to 2/3 of its target distance, when the target is at ranges in excess of 300 yards. At that point, the round begins its descent onto the target. The projectile will be given slight lift from the turbulence that forms on the top of the round as it drops toward the target. This gives the round a slightly longer time of flight than would be expected from pure physics. d. When zeroing the service rifle at 300-yards with the M855, all projectiles exiting the barrel will have to travel upward to meet the line of sight at 36-yards, and back down to cross the line of sight again at 300-yards. The effects of zeros at combat range become apparent, especially when comparing a 300-yard zero with a 200-yard zero and a 500-yard zero. e. Long range ballistics show how the round must drop

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heavily into the target. The distance at which the round will be in the lethal area is very small. f. With a 300-yard zero, all shots at less than 36-yards will be lower than the sight picture. With a 200-yard zero, the same is true at 55-yards. This is especially important at close range due to the height of the optic over the bore. To place a round precisely, the shooter must aim higher than the intended impact point. g. Minute of Angle (MOA) is a commonly used term to describe accuracy. (1) It may explain the accuracy of a weapon, performance of ammunition, ability of a shooter, or a combination of these aspects. (2) Minute of Angle (MOA) depends on size and range. It is an expression of an angle, so size will increase as range increases. One inch, at 100-yards, equals 1 minute of angle. Though 1 MOA is not actually 1 inch, the difference is so miniscule it does not come into effect at any range that can be engaged with shoulder-fired weapons. At 1,000 yards, the difference is only .476 inches, hardly enough to make a difference. (3) Minute of angle is determined not only by the size of the group, but also the range at which the group was fired. 2 inches at 200-yards is 1 MOA. 2 inches at 100-yards is 2 MOA. 1 inch at 200-yards is or .5 MOA.

(4) If a weapon holds a certain size group at one range,

the group will spread or shrink proportionally according to distance. Simply divide the group size by hundreds of yards to determine the minute of angle, or multiply the minute of angle by hundreds of yards to determine group size. One caveat to this is that just because a weapon can produce a group of 1 inch at 100-yards, it does not necessarily mean that it will produce a 5-inch group at 500-yards. The projectile may not be stable throughout its flight, allowing drag or wind to cause a slightly different trajectory for each round fired. 3. TERMINAL BALLISTICS: Terminal ballistics is the study of the projectile once it strikes its target and the effect on the target. For the purposes of this period of instruction, the target is the human body. It is the examination of what is

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occurring when the projectile makes impact, what happens as it travels through tissue, how the projectile reacts when in tissue, and projectile-tissue interaction.

a. Myths Surrounding Terminal Ballistics: There are many myths about terminal ballistics circulated by unknowledgeable individuals and ammunition manufacturers. Some of the most frequent misunderstandings are as follows:

(1) Human targets will fly backward when shot. (2) Entrance wounds will be huge holes spurting blood. (3) A human will instantly die when shot. (4) A shot to the heart will instantly kill a human

threat. (5) Any shot to the head will cause instant death.

(6) Bullets will bounce around inside the body.

(7) Any high velocity round will kill a target due to

Hydrostatic Shock, which instantly destroys organs regardless of shot placement.

(8) There is a mathematical formula that can determine

knock-down power of a given round. (9) Numerical values of foot pounds of energy, or energy

transfer, are indicative of a rounds ability to stop a threat. (10) Bigger bullets will always out-perform smaller

bullets. b. When the projectile makes initial impact with the target it is unlikely that the bullet will be perfectly aligned with its flight path, due to constant precession. Additionally, the gyroscopic stabilization imparted by the rifling will keep the round pointed in the same direction as the barrel. Gyroscopic stabilization causes the round to resist changes in orientation. As the bullet begins its penetration into a human target, it will produce a puncture wound in the skin and will not be deformed or fragmented.

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c. The puncture wound will be smaller than the diameter of the bullet that produced it because the skin will stretch before the bullet punctures the skin. d. As the round continues into flesh, its slight offset orientation will cause friction on the front and bottom of the projectile. This bullet-tissue interaction will cause the round to tumble, with the point of the bullet generally moving upward and the base rotating down and forward. The impact of the round on the wet tissue of the body will impart energy and velocity to the surrounding tissue. This creates a cavity within the flesh, but does not cause any real damage itself. e. The temporary cavity is easily visualized by thinking of a large rock dropped into a puddle. The water will rapidly move away from the rock, creating a large hole in the water around the rock that quickly closes. This is called the Temporary Cavity, and it will close itself in a matter of milliseconds. f. Depending on the round and its velocity, the round may either stay in essentially one piece or break apart into several smaller pieces. (1) If the round breaks apart (fragmentation), it will cause several small wound tracks, as the individual pieces of the round will each follow different paths. The round may stay in one piece though, causing damage only to the tissue the projectile directly contacts. The target will suffer tearing and crushing wounds to the tissue directly contacted by either the fragments or the round itself during its passage through flesh. (2) This destruction is the Permanent Wound Cavity, and is responsible for real system trauma within the body. The amount of penetration a projectile achieves in tissue is important to terminal ballistics, but alone is not an indicator of success. (3) The round must penetrate sufficiently to reach and destroy vital areas of the human target. Any additional penetration is unnecessary, and may even be detrimental due to over-penetration and resulting injury, to personnel other than the intended target.

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(4) When the round is traveling at high speed, it has a higher probability of rapid fragmentation, and thus lesser penetration than a slower projectile. (5) The slower projectile (less than 2600 f/s) will usually penetrate more deeply with lesser or no fragmentation within a human target. This is also applicable to common obstacles such as wood. With metal however, the steel penetrator of the M855 will benefit from high velocity, penetrating more deeply at higher velocities.

g. When the temporary cavity is created within the target, the stretching action can further tear the small wound tracks produced by fragmentation. In this respect, the temporary cavity assists the permanent wound cavity, but is not an indication of effectiveness or stopping power alone.

h. There is no hydrostatic shock imparted to the target by

the temporary wound cavity. Even when multiple shots strike a target, the primary wounding mechanism is rapid fragmentation / tissue destruction. Hydrostatic Shock is the process in which energy is transmitted through a body of water at the speed of sound through that medium. The theory places high value in temporary cavity, which is non-destructive, with a single round. This is not damaging to a human body due to its elastic composition and the fact that force is transmitted radially outward from a projectile. i. The temporary cavity closes rapidly, causing no lasting damage unless it occurs in inelastic (non-stretching) tissue such as the liver, kidneys or brain, or the skin during the rounds exit from the body. These organs or skin will be ripped apart by the temporary cavity pressure wave since they do not stretch as well as other organs, fat, and muscle. j. The tissue that was crushed and torn by the projectile will remain open as the Permanent Cavity. k. Ballistic gelatin is used to determine a rounds performance in flesh. It does not account for bones, thick muscle, air in the lungs, etc. What it shows is an educated guess as to what will happen in a human body. Penetration in a human body will be about 4/5 of the ballistic gelatin. Notice that the permanent cavity is about the same size as the projectile and is surrounded by the temporary cavity. The

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closer the round comes to stopping, the less energy has been available to maintain the temporary cavity. l. The amount of yaw a bullet has when striking a target (angle of incident) is also a factor in the amount of fragmentation and penetration that the round will exhibit. A low angle of incident, as when the round is very stable or the yaw angle is in line with the flight path, will allow the round to deeply penetrate with a minimum of fragmentation. Conversely, a high angle of incident will cause the projectile to rapidly yaw and fragment. This will be true even if the striking velocity is relatively low. m. It becomes apparent that yaw is related to fragmentation. This can lead the casual observer to come to the conclusion that the larger amount of yaw inherent to the projectile, the better. However, keep in mind that high yaw (achieved through precession) is detrimental to accuracy, especially at ranges over 100-yards. n. The M855 traveling at high speed produces not only an impressive temporary cavity, but also a large permanent cavity due to the rounds fragmentation. This large permanent cavity inside the body is what is responsible for eliminating a threat with a small caliber projectile. o. On this slide you can see the various wound components, as illustrated by rounds fired into ballistic gelatin. The 5.56mm ball at high speed energetically fragments. As the velocity decreases, so too does the potential for fragmentation. The round is most effective at no less than 2,500 feet per second, which occurs at 200-yards from a 20-inch barrel with a muzzle velocity of 3,100 feet per second. By 300-yards (2,225 f/s), this fragmentation is completely lost. 4. EFFECTS OF SHOT PLACEMENT: a. The Brain: This is the only one-shot technique that will lead to immediate incapacitation of a threat. The brain is broken down into three main parts: (1) The Cerebrum is responsible for higher functions such as intellect and awareness of self. It is the largest part and surrounds the rest of the brain structure. (2) The Cerebellum is the second largest part and is

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responsible for voluntary movements. (3) The Medulla Oblongata connects the brain to the spinal cord and controls involuntary functions. It is the most critical but smallest part of the brain. b. To immediately incapacitate a target, destroy the Medulla Oblongata. To effectively target the Medulla Oblongata, you must get the bullet to enter the central Cranial Cavity. (1) The Medulla Oblongata is a small target, but a high-velocity round that enters the brain will produce a destructive temporary cavity, along with probable fragmentation and secondary bone fragmentation. (2) The brain, when alive, is soft and pliable, similar to gelatin. The temporary cavity will separate brain cells, destroying the integrity of the brain. If the projectile enters the cranial cavity relatively near the Medulla Oblongata, it will also be destroyed, resulting in instant incapacitation. However, if the bullet is low, it will not enter the cranial cavity, and will not destroy the medulla oblongata. (3) The bullet may pass through the teeth, jaw, or throat, and hit the spinal column, but an impact to this area will not have the high incapacitation probability of a properly placed shot. c. Immediate Incapacitation Strike Points for the Head: When shooting a person in the head with the intent to immediately cease their actions, we must destroy the medulla oblongata. Since we cannot see it inside the head, we can select points outside that correspond to its location inside. (1) A frontal shot should be placed within the T-Box which is located from the brow to the bottom of the nose and from eye to eye. This is a direct path to the medulla oblongata and is also the weakest part of the head. A T-Box shot easily penetrates the head with minimal deflection or energy loss. (2) A side shot should go through either the ear or temple. Be aware that a shot to the temple is risky; it may lead to nothing more than a lobotomy or extraction of the eyes due to the bone structure of the skull.

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(3) For a high angle shot, aim for the hairline so that the round travels through the medulla oblongata to the base of the skull.

d. Vital Areas of the Body: Shots to these areas of the body will likely cause death, but not all are reliable for immediately incapacitation: (1) The base of the throat is packed with vascular structures and nerves, and is backed by the spine. A shot to this area has a high probability of causing death unless immediately medical attention is given. Shots to this portion of the anatomy has a high chance of instant incapacitation, but its small size and location make anything but surgical precision ineffective. (2) The upper portion of the heart and the structures above the heart are highly vulnerable to piercing. A shot to this area will cause rapid decompression and death. Two shots in rapid succession to this area have a hugely higher chance for instant incapacitation than a single shot to the same area. (3) The lower portion of the heart is tougher than the upper part, and will bleed more slowly, but with the same eventual result; death. (4) The kidneys are fragile, but both must be destroyed to cause death or incapacitation in a timely manner. A penetrating strike to a kidney will cause involuntary clenching. This is not a preferred target, and intentional targeting should be reserved as a last resort only. (5) The liver is not elastic and the temporary wound channel will destroy this organ. The liver is not a preferred target as it will not cause immediate incapacitation.

e. Targeting the Skeletal Structure: In some circumstances it may be beneficial to stop a target from moving. (1) A shot to the pelvis has a high probability of fracturing the pelvis. The pelvis bears the weight of the body, and its destruction will cause a human to fall, unable to bear weight with the legs. The destruction of the pelvis will not incapacitate the threat in a rapid time frame, but it will

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prevent the threat from seeking cover or continuing rapid movement. The pelvis is a large target, and may be more easily targeted than the head, especially when the target is moving.

(2) The pelvis is located approximately 1-2 inches below the navel. It is roughly 11-inches wide. The sides of the pelvis angle downward at roughly 30 degrees toward the groin. The bottom of the pelvis is approximately 6-inches wide, and the hips join at the bottom portion of the pelvis. The bottom portion of the pelvis lies above the genitals.

f. Achieving Incapacitation: There are numerous theories as to what increases the probability of incapacitating a hostile threat. Every possible mechanical theory has been offered, from the Big Hole Theory to Hydrostatic Shock, and onto blaming or praising certain types or manufacturers of ammunition. These hypotheses have been regularly disproved, and with each that have been disregarded, more have sprung up in their wake. Nevertheless, the most pertinent issues to incapacitation are undeniable. These basic tenants of combat marksmanship are far more relevant to incapacitation than what bullet strikes the threat.

(1) Engagement Techniques: (a) Pairs. Two rapid shots to the upper central

thorax will destroy the major vascular structures, increasing blood loss and the onset of shock.

(b) Precision Shots. Placing a round exactly where

it is needed is the duty of the rifleman. Knowing where a single shot should land to immediately incapacitate a threat, and making sure it finds its way there, will remove the threat and save lives.

(2) Shot Placement: (a) High Center Mass. The highest probability of

destroying a major circulatory system is when the projectile enters the high in the central thoracic cavity. This leads to rapid blood loss and incapacitation. Placing two rounds in the same area raises that chance greatly. (b) T-Box. A round that pierces the ocular-cranial cavity (or the ear area for a side-shot), will destroy the medulla oblongata, immediately ceasing all action.

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REFERENCES: MCO 3574.2L MARINE CORPS MARKSMANSHIP PROGRAM