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Part I: Types of Wounds and Injuries: Chapter II: Missile-Caused Wounds

Mechanisms of Wounding
United States Department of Defense
Peer Review Status: Internally Peer Reviewed

The penetrating missile or fragment destroys tissue by crushing it as it punches a hole through the tissue. This hole or missile track represents the so-called permanent cavity. The cross-sectional area of the missile track is comparable to the presenting area of the missile and its dimensions are roughly the same for all soft tissues.

After passage of the projectile, the walls of the permanent cavity are temporarily stretched radially outward. The maximum lateral tissue displacement delineates the temporary cavity. Any damage resulting from temporary cavitation is due to stretching of the tissue. Resistance or vulnerability to stretch damage depends mostly on tissue elasticity. The same stretch which causes only moderate contusion and minor functional changes in relatively elastic skeletal muscle, can cause devastating disruption of the liver. The result of temporary displacement of tissue is analogous to a localized area of blunt trauma surrounding the permanent cavity left by the projectile's passage.
The typical wounding potential of a given missile can be assessed by measuring the two types of tissue disruption it produces. A method developed by U.S. Army researchers captures the entire path of missiles fired through gelatin tissue-simulant blocks. Measurements taken from the gelatin are used to illustrate the location and the extent of both crush and stretch types of tissue disruption on a drawing or "Wound Profile." The scale included on each profile can be used to measure the extent of tissue disruption on a drawing at any point along the path of the projectile. This method allows comparison of the wound profiles of different of different wounding agents.
The sonic shock wave seen at the far right of precedes the projectile's passage through the tissue. Although the magnitude of the sonic wave may range up to pressures of 100 atmospheres, its duration is so brief, about 2 microseconds, that it does not displace tissue. It has no detectable harmful effect on tissues.

Projectiles
United States Department of Defense
Peer Review Status: Internally Peer Reviewed

The following is a compendium of the characteristics of the more commonly encountered small arms projectiles. Note that the projectiles depicted in numbers 1-7 do not deform upon passing through soft tissues, whereas those in numbers 8 - 13 either deform or fragment, forming secondary bullet fragments. Projectile deformation, fragmentation, yaw and individually or collectively increase the resultant degree of tissue disruption.
1. 45 Automatic - This full-metal-jacketed military bullet is one of few that does not yaw (turn the long axis in relation to direction of travel) significantly in soft tissue. Lack of yaw, coupled with the large mass of this bullet, results in deep penetration. The crush tissue disruption remains nearly constant throughout the bullet path. Temporary cavity stretch is maximal near the point of entry, gradually diminishing with penetration, but with this bullet type and velocity the temporary cavity is too small to show a stretch wounding effect.
2. 22 Long Rifle - This commonly used rimfire bullet yaws through 90 degrees and ends up traveling base forward for the last half of its tissue path. The crush tissue disruption increases with yaw angle, reaching its maximum when the bullet is traveling sideways. Temporary cavity stretch increases with increasing bullet yaw, much the same as a diver hitting the water makes a larger splash as his body angle to the water surface increases. Even at the point of maximum bullet yaw, the temporary cavity produced remains too small to add a detactable stretch wounding effect.

3. 38 Special - This round-nosed lead bullet like the 45 Automatic and the 22 Long Rifle produces its wounding almost solely by the crush tissue disruption mechanism. Although still too small to show an observable stretch wounding effect, the maximum temporary cavity is of 20% greater diameter than that made by the 22 Long Rifle despite the fact that its velocity is 40% less.
4. 9 mm Parbellum - This bullet is widely used in both pistols and submachine guns. As with the full-metal-jacketed bullet type, it produces a profile that resembles that of the .38 Special, but the maximum temporary cavity is about 2 cm larger in diameter and will show some stretch effects (radial splits) in less elastic, more susceptible tissues such as those of the liver.
5. 7.62 NATO FMC - FMC is the abbreviation for full-metal-cased, which is a synonym of full-metal-jacketed. This refers to the harder metal covering of the bullet core. This full-metal-jacketed military bullet shows the characteristic behavior in tissue observed in non-deforming pointed bullets. It yaws through 90° and, after reaching the base-forward position, continues the rest of its path with little or no yaw. The bullet is stable traveling base first in tissue, since this position puts its center of mass forward. The rotation imparted to the bullet by the rifled gun barrel is sufficient to cause point-forward travel in air, but not in tissue where such factors as bullet shape and location of center of mass outweigh rotation effects. The tissue disruption in the first 15-18 cm of bullet penetration, during which the streamlined bullet is still traveling point forward, is minimal. At 20-35 cm, however, in which bullet yaw is marked, a large temporary cavity is produced. If the bullet path is such that this temporary cavity occurs in the liver, this amount of tissue disruption is likely to make survival improbable.

6. AK-47 - The Russian Assault Rifle's full-metal-cased military bullet travels point forward for 25-27 cm in tissue prior to beginning significant yaw. Wounds from this rifle are familiar to surgeons who served in Vietnam and have been documented by the WDMET study of wounds from that conflict.


7. AK-74 - This new generation, smaller caliber Russian Assault Rifle follows the example set by the USA with the M-16. The full-metal-cased bullet designed for this weapon has a copper-plated steel jacket, as does the bullet of its predecessor, the AK-47. A unique design feature of the AK-74, however, is an air space (about 5 mm long) inside the jacket at the bullet's tip. The speculation that this air-space would cause bullet deformation and fragmentation on impact proved to be unfounded, but the airspace does serve to shift the bullet's center of mass toward the rear. This bullet yaws after only about 7 cm of tissue penetration, assuring an increased temporary cavity stretch disruption, even in many extremity hits. The typical exit wound from a soft-tissue thigh wound (12 cm thick) is stellate, with skin split measuring from 9-13 cm across. The underlying muscle split is about half that size. The bilobed yaw patterns shown in the profiles of the AK-47 and the AK-74 represent what is seen in four-fifths of test shots. In the rest, the bullet reaches 90° of yaw and continues to 180° or the base, forward position, in one cycle. Whether there are one or two yaw cycles does not influence the point of prime clinical relevance- the distance the bullet travels point forward before yaw. The bilobed yaw pattern results from initial bullet yaw returning to zero yaw (first lobe), but then yawing a second time (second lobe) to 180° where the center of mass stabilizes the projectile in base forward navel.
Figure 9
8. 357 Magnum JSP - The jacketed soft-point bullet and the jacketed-hollow-point bullet flatten their tips on impact. This "expansion" or "mushrooming" (in which the final bullet shape resembles a mushroom) results in a doubling of effective bullet diameter in tissue, and allows the bullet to crush four times as much tissue (¹ times radius squared equals the cross section area of the bullet which impacts tissue). This conversion of the bullet to a non-aerodynamic shape causes the same sort of increased temporary cavity tissue stretch as does the yawing of a bullet. The maximum temporary cavity produced by the expanding bullet occurs at a shallower penetration depth than that caused by the full-metal-jacketed military type bullet. This soft-point pistol bullet is typical of the type most commonly used by law enforcement agencies in the USA. Its decreased penetration depth, as compared to the depth of penetration of the nondeforming bullets decreases the likelihood of the bullet perforating a criminal and going on to injure an innocent bystander.

9. 7.62 SP - (SP is the abbreviation for soft-point) The same cartridge case shown in when loaded with a soft-point bullet, produces the wound profile shown in Changing only the variable of bullet construction causes massively increased tissue disruption compared to that of the full-metal-cased bullet. Bullet expansion occurs on impact as seen with the 357 Magnum pistol bullet; however, the crush in the tissue that results from bullet expansion accounts for only a small part of the large permanent cavity. As this bullet flattens, pieces break off and make their own separate paths of crushed tissue. These bullet fragments penetrate up to 9 cm radially from the bullet path. The following temporary cavitation stretches muscle that has been weakened by multiple perforations. The fragment paths act to concentrate the force of the stretch, increasing its effect and causing pieces of muscle to be detached. This synergistic effect, resulting in the large tissue defect, is seen only with bullets that fragment. The 7.62 NATO soft-point is a popular big game hunting bullet, and although shooting accidents are not infrequent with such rounds, they are rarely seen in the hospital since few victims of torso shots survive.

10. 22 CAL FMC - This is the M-193 bullet shot from the M-16A1 Assault Rifle. The large permanent cavity shown in the profile was observed by many surgeons who served in Vietnam, but the tissue disruption mechanism responsible was not clear until the importance of bullet fragmentation as a cause of tissue disruption was worked out. This military round is full-metal-jacketed and, as with other bullets of this type, it causes little tissue disruption so long as it remains traveling point forward through tissue. Its average distance of point-forward travel is about 12 cm, after which it yaws to 90°, flattens, and breaks at the cannelure (groove around bullet mid section). The bullet point remains a flattened triangular piece, retaining about 60% of the original bullet weight. The rear portion breaks into many fragments that penetrate up to 7 cm radially from the bullet path. The temporary cavity stretch, its effect increased by perforation and weakening of the muscle by fragments, then causes a much enlarged permanent cavity by detaching muscle pieces. The degree of bullet fragmentation decreases with increasing shooting distance, as striking velocity decreases. At a distance of 80 meters, the bullet breaks in half, forming two large fragments. At ranges in excess of 180 meters, this projectile does not break in two and the wounding capacity and mechanisms are essentially the same as those of the AK-74.

11. M-855 22 CAL FMC - The slightly heavier M-855 bullet shot from the M-16A2 Assault Rifle will eventually replace the M-193 bullet shot as the standard bullet for the U.S. Armed Forces. The wound profile is similar to that produced by the M-193, although the tip generally does not remain in one piece. The temporary cavity size and location are about the same and any difference in wounds caused by the two would be cliff cult to recognize.
The smaller bullets of the new generation Assault Rifles (M-193, AK-74, M-855) are susceptible to deflection and disturbance of their point-forward flight by intermediate targets such as foliage. This was not the case with the previous generation of larger and slower projectiles. This can result in large yaw angles at impact and a shallower location in the body of maximum tissue disruption. For these bullets that rely on yaw in tissue for their maximum effect, the wound profiles show the average penetration depth at which this yaw occurs.
12. .224 Soft-point - This 50 grain soft-point bullet is designed for maximum deformation and fragmentation. To produce the wound profile shown in, it was shot from the M-16 cartridge case (known as the 223 Remington in civilian shooting parlance). The amount and type of damage caused is about the same as that caused by the military M-193 (M-16) bullet, but the location of the maximum disruption is at a shallower penetration depth.

13. 12 Gauge Shotgun #4 Buckshot - Loaded with 27 pellets of #4 Buckshot, the 12 gauge shotgun at close range (3 meters in this case) causes massive crush type tissue disruption. At this short range, soft- tissue impact deforms the individual pellets, increasing their original 6 mm cross section to about 10 mm with concomitant increase in tissue crush or hole size. The 27 perforations of this size in a 7-8 cm diameter area result in severe disruption of anatomy by direct crush and in disruption of blood supply to tissue between the multiple wound channels.

The foregoing wound profiles portray an estimate of the maximum soft-tissue disruption expected at short ranges (under 25 meters). A gradual decrease in the amount of bullet deformation, fragmentation, and maximum size of the temporary cavity occurs with distance as the striking velocity of the projectile decreases. When bone is struck by the penetrating projectile, the result is predictable and easily verified on X-ray. Total penetration depth will be less; however the degree of tissue disruption will be greater due to increased ,projectile deformation and the creation of secondary bone fragment missiles.

Reprinted form the original text by:

Thomas E. Bowen, M.D.
Editor
BG, MC, U.S. Army
Ronald Bellamy, M.D.
Co-Editor
COL, MC, U.S. Army

United States Department of Defense

United States Government Printing Office
Washington, D.C.
1988

Peer Review Status: Internally Peer Reviewed


<font size=-1>[ This Message was edited by: David DiFabio on 2001-06-27 00:04 ]</font>
 

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Thanks David, there is some VERY useful info here :smile:
 
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Discussion Starter · #3 ·
More info from the above with "medical" reference stressed in lieu of the normal ballistic importance.
DD

Introduction
United States Department of Defense
Peer Review Status: Internally Peer Reviewed

The emphasis of this chapter is on the management of damaged muscle Surgical management of other soft tissue and bone injuries is dealt with in other chapters. Two separate mechanisms are responsible for the injury caused by the passage of missiles through tissues.

As the projectile punches through muscle, it destroys the tissue in its direct path by crushing it.

Temporary cavitation forces, which present about one millisecond after passage of the projectile, stretch the tissues adjacent to the permanent missile track and result in additional injury or destruction.


Crushed Muscle: The amount of crushed muscle resulting from a single bullet or single fragment is closely related to the presenting cross-sectional area of the projectile. The gross anatomy of muscle will be much more severely disrupted by multiple penetrating projectiles striking in close proximity to each other, as is the case with explosive device injuries, deforming or fragmenting rifle projectiles, or any rifle projectile that strikes bone. Some remnants of muscle crushed by penetrating projectiles will generally be seen as a frayed edge along the missile track. Detached pieces of muscle, partially detached muscle flaps, and muscle islands surrounded by perforations should be regarded as nonviable. They would most likely act as foreign bodies that will potentiate infection in an already contaminated wound.


Stretched Muscle: Temporary displacement of muscle by cavitation can cause petechial hemorrhages from torn small vessels (contusion), thrombosis of other small vessels, and patchy broken muscle fibers. Cavitation follows the path of least resistance, which is most often to separate muscle between parallel fibers and bundles. Gross radial splits are sometimes seen in muscle but not nearly to the extent that they are seen in skin. Although both bullet yaw and bullet deformation appreciably increase the dimensions of both the permanent and the temporary cavities, the effects of bullet fragmentation are by comparison devastating, and may result in an injury that is multiplied by several orders of magnitude in muscle that has been weakened a millisecond earlier by the creation of multiple radial fragment tracks.

Excerpted from the original text by:

Thomas E. Bowen, M.D.
Editor
BG, MC, U.S. Army
Ronald Bellamy, M.D.
Co-Editor
COL, MC, U.S. Army
United States Department of Defense
United States Government Printing Office
Washington, D.C.
1988
Peer Review Status: Internally Peer Reviewed
Creation Date: Unknown
Last Revision Date: 1988



_________________
Think, Plan, Train, Be Safe.
Thanks,
David

<font size=-1>[ This Message was edited by: David DiFabio on 2001-06-27 00:22 ]</font>
 

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David, I just read all of your current posts and it is quite a "handfull" of information, which I will have to read at least once more.

The elasticty of the of the human body is well illustrated by surgery preformed and the amount of retraction that that can be done to gain access, for example the cervical spine through the anterior of the cervix (neck).

Thanks again for the informative posts. Mike
 
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Discussion Starter · #5 ·
Randall,
If you have experience as a trauma or reconstructive surgeon I would like to talk with you offline as I have been working on an extended project as involving bone fragmentation and vascular microtearing with ligament/connective tissue rupture.
 

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Let me summarize some of the results and ask a question or two (I know nothing about wound ballistics.)

1. It appears that the greater effectiveness of rifle bullets comes primarily from both the temporary and permanent wound cavities created during the yaw phase when the bullet swaps ends in its travel thru tissue.

Is it the greater velocity of the rifle bullet that is the requesite for the difference in yaw vs. pistol bullets?
If not, what causes the yaw in rifle bullets?

2. A mushrooming pistol JHP can simulate the rifle bullet yaw effect, but at a shallower depth.

Is the greater energy of the rifle bullet the deciding factor in this difference?
(I realize this creates the difficulty of not mentioning other variables which are related, e.g., energy and velocity.)

3. A fragmenting (or pre-fragmented?) bullet is more effective in creating tissue damage than a bullet with identical weight, caliber, and speed in FMJ or JHP configurations which do not happen to fragment.

Thus, in rifle vs. pistol bullet "effectiveness" (tissue damage),it is not caliber which is a significant factor (30 cal. rifle vs. 45 cal. pistol).
Fragmentation appears significant (a characteristic I have heard described elsewhere as a negative for bullet performance.)
Energy does make a significant difference (if observation 2. is correct).
The variable(s) (whatever they are) which cause a bullet to yaw are highly significant in bullet performance.

Please help me through the maze.



<font size=-1>[ This Message was edited by: SELFDEFENSE on 2001-09-06 11:17 ]</font>
 
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