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The two-shot technique is an effective stopping power method. The precise mechanisms of action on the bone and soft-tissue structures of the skull; however, remain largely unclear. The aim of this study is to compare the terminal ballistics of the two-shot and single-shot techniques.
40 fresh pigs’ heads were randomly divided into 4 groups (n = 10). Either a single shot or two shots were fired at each head with a full metal jacket or a semi-jacketed bullet. Using thin-layer computed tomography and photography, the diameter of the destruction pattern and the fractures along the bullet path were then imaged and assessed.
A single shot fired with a full metal jacket bullet causes minor lateral destruction along the bullet path. With two shots fired with a full metal jacket bullet, however, the maximum diameter of the bullet path is significantly greater (P < 0.05) than it is with a single shot fired with a full metal jacket bullet. In contrast, the maximum diameter with a semi-jacketed bullet is similar with the single-shot and two-shot techniques.
With the two-shot technique, a full metal jacket bullet causes a destruction pattern that is comparable to that of a single shot fired with a semi-jacketed bullet.
Military combats have changed in the course of time. Changed operational conditions mean that today's conflicts no longer comprise a conventional combat between 2 groups of enemies but an asymmetrical battle situation. To an increasing extent, these battles are not only fought from afar but often from close distances with a battle range of less than 30 m. This low battle range calls for prompt stopping power against an aggressor in order to immediately incapacitate the enemy. As a consequence of the new developments on the battlefield, a new marksmanship training concept was prepared and drawn up amongst the North Atlantic Treaty Organization (NATO) alliance partners in August 2010. This joint concept complements the exercises that have existed so far and is designed to meet the new battlefield conditions while at the same time increasing efficiency.
In the wake of the increasing number of battles in Afghanistan and Iraq, discussions were held on the ammunition used by NATO troops that turned out to be particularly ineffective at distances beyond 200 m. In combination with a lack of effectiveness and a reduction in combat range, stopping power, i.e., incapacitation, must also be taken into account. With full metal jacket bullets, which the Armed Forces generally use as prescribed by the international law of war, stopping power, on the other hand, stands in contrast with target effect.[4,5] To overcome this problem, the two-shot technique was incorporated into the new marksmanship training concept. This technique involves firing two shots at each target, the aim being to mathematically increase impact energy and to intensify the effect on the target. The exact destruction patterns and terminal ballistics have not yet been examined.[6,7] Experience gathered so far from combat confirms the effect of the two-shot technique but does not sufficiently explains it. From the military conflicts that have taken place to date, we have no medical data on its exact mechanism of action.
As a military projectile, the main bullet examined was the full metal jacket bullet. Since weapons, however, are not only used in military environments but also in terrorist attacks or outside the Geneva Conventions, this study also looks at semi-jacketed bullets. To establish the various destruction patterns, an animal carcass model was chosen. These carcasses were fired at under standardized conditions with full metal jacket and semi-jacketed bullets using the single-shot and the two-shot techniques, the aim being to examine a fundamental injury pattern.
As it penetrates the tissue, the projectile centrifugally accelerates it and displaces it sideways (radially), i.e., at a right angle to the bullet path, causing a temporary wound cavity whose diameter can be 4 times the size of the actual bullet. Immediately after the kinetic energy of the radially displaced tissue has been fully exerted there is a centripetal movement back in the opposite direction — a suction effect — towards the geometrical bullet path. When this backward movement is complete, a definitive secondary wound cavity remains. Bones are considerably denser, heavier and less elastic than soft tissue. Depending on the structure, speed and ballistic coefficient of a bullet when it comes into contact with a bone, the bullet and its movement behavior can change. Bone contact can cause a projectile to wobble, deform it, and in some cases even fragment it. This would cause its ballistic co-efficiency to decrease, involving increased energy output. Essentially, this energy is used to bring about the fracture and secondarily, to accelerate the bone fragments. The skin also changes when penetrated by a bullet. Since the impact of the bullet also causes radial tissue acceleration, the skin opens — while the projectile is penetrating it — to form a hole that is for a brief moment larger than the bullet's caliber. After the bullet has penetrated, the skin's elastic force allows it to contract again. The result is a bullet hole that is usually a little smaller than the caliber of the bullet. During bullet exit, the projectile comes out of the target's body and initially causes the skin to curve outwards before finally causing it to tear. This is why bullet exit wounds are slit-shaped and have an irregular configuration. Due to the complexity and composition of various tissues (skin, bone, muscles, etc.), this study did not use gelatin or soap blocks as targets.
Although we know that the two-shot technique with a full metal jacket bullet is effective, the pathomechanism behind it remains unknown. Using an animal carcass model, this study looks at the differences between a full metal jacket bullet and a semi-jacketed bullet using the single-shot and two-shot techniques.
In order to compare the effect of the two-shot technique on the bone and soft-tissue structures of the skull with that of the single-shot technique, the heads of 10 fresh domestic pigs (n = 10 per group) were shot at with various types of bullets. In each case, the bullet travelled from the occipital medial area towards the naso-ethmoidal complex. For each of the 4 groups, 10 pigs’ heads were examined. The 1st group was shot at with a full metal jacket bullet using the single-shot technique. The 2nd group was shot at with a full metal jacket bullet using the two-shot technique. Groups 3 and 4 were shot at with semi-jacketed bullets, using the single-shot technique for group three and the two-shot technique for group 4. Prior to each test, the pig's head was firmly secured in a fixing device. After the heads had been secured and following photographic documentation, the heads were shot at in accordance with their group. The tests were carried out using different calibers as specified in Table 1.
The targets were shot at from a hunting platform using a conventional rifle leaning on a secure ledge. Each shot was photodocumented in detail. For the single shot, an assessment was then carried out by means of thin-layer spiral computed tomography (CT) (GE LightSpeed 16 VFX) with a slice thickness of 0.6 mm. For the examination of the two-shot technique, the two shots were taken without interruption. Photographic documentation was then also performed in order to assess the destruction pattern of the soft tissue and assess the bone destruction pattern by means of CT imaging. The image data obtained (photograph and CT) of the single-shot pattern was compared with that of the double-shot pattern and assessed. On the basis of the photographs, a comparative analysis was performed of the changes to the skin around the bullet exit area, and CT data sets were used to compare the effects on the bone. First of all, the data set from the single shot in the sagittal area was examined and adjusted in such a way that the largest diameter in the craniocaudal axle at the level of the bullet path was visible. Its length and width were then measured, and the entry wound was defined as A, the exit wound as B, and the middle between points A and B was defined as C. The individual points were then measured for all carcasses within the group. Firstly, the distance between A and B was measured, followed by the diameter of the secondary wound cavity at point C. An analogous procedure was used in the other groups. Alignment within the sagittal level was always based on the largest diameter of the damage in the craniocaudal axle. The results for each point were statically averaged (standard deviation) for each group and were compared with the other relevant groups. The assessment was carried out using Microsoft Excel (Microsoft Office XP 2002, Microsoft Inc.)
Although all the full metal jacket bullets had the same energy, this bullet revealed a significantly more distinct destruction pattern with the two-shot technique than it did with the single-shot technique. In the case of the single shot fired with a full metal jacket bullet, the entry wound and the exit wound are approximately the same size, as described in the relevant literature.[13,14] The tissue damage resembles an almost circular cavity. With the two-shot technique, the entry and exit wounds are somewhat bigger, concentric and inhomogeneous in texture.
As regards destruction pattern, the radiological analysis reveals that a single shot fired with a full metal jacket bullets causes destruction along the bullet path that includes the dislocation of individual fragments and the formation of fractures radially from the bullet path. The two-shot technique not only results in a destruction pattern along the bullet path but also a much larger wound cavity. On average, the wound cavity is 69.9% larger than with a full metal jacket bullet fired with the single-shot technique. There is therefore an almost exponential increase in the destruction pattern as opposed to the single-shot technique. Here, there is no distinct dislocation of bone fragments, and the destruction pattern along the bullet path takes the form of tears and only minor dislocation.[15,16] The bone margins are clearly defined and depending on the bullet's entry angle, the wound of entrance is circular to elliptical in shape. On the exit side of the bone there was an injury that formed as a result of displacement effects and that expanded in the shape of a funnel in the direction of the gunshot.
As regards kinetics, the results are also similar when comparing the single-shot and two-shot techniques using a semi-jacketed bullet. The destruction patterns with the semi-jacketed bullet are not comparable with those of a full metal jacket bullet, and the change in diameter of the secondary wound cavity when comparing the semi-jacketed bullet using the single-shot and two-shot techniques with the full metal jacket bullet using the two-shot technique is insignificant (P < 0.05). A comparison of the full metal jacket bullet using the single-shot technique with the full metal jacket bullet using the two-shot technique, the semi-jacketed bullet using the single-shot technique and the semi-jacketed bullet using the two-shot technique revealed an increase in diameter in the primary bullet path in all three cases [Table 2, Figures Figures11--4].4]. To summarize, it appears that the changes in the secondary wound cavity in the body with the single-shot and two-shot techniques and a semi-jacketed bullet are the same as with the two-shot technique and a full metal jacket bullet.
Since the purpose of this study is to examine the effect of various gunshot patterns on the body, where various structures such as skin, bones, muscles etc. interact, soap and gelatin blocks are not suitable as models. Although gelatin is the ballistic target medium that best corresponds to the density ratio of muscle tissue, it only represents one medium.[18,19] In addition, a model is needed that is large enough to reflect the gunshot and its consequences as realistically as possible and to permit a relevant assessment. Pigs’ heads are a complex model for simulating gunshot wounds. They feature various anatomic structures that are similarly configured in humans. The pig, however, is limited in the extent to which it can be used as a model because its skin is thicker and its lower jaw has different proportions. This study was subject to some restrictions. With regard to its morphology, surface structure and mass distribution, a pig's skull is not entirely comparable with that of a human. For this reason, the results are only transferrable to a certain degree. However, since the study involved a comparative analysis of the results, they are transferrable. In this study, the pathophysiological procedures with the single-shot and two-shot techniques are examined with different projectiles. For this reason, the results can indeed be transferred from pigs to humans. It is hoped that further studies will be carried out on human preparations.
Gunshots are extremely fast processes. The interaction between an entering and penetrating bullet and the target occurs within a few milliseconds. A bullet moving through soft tissue at high speed affects the tissue. At the same time, the tissue also affects the bullet. Things look different with a gunshot through a bone. In this case, the path of the bullet/wound in the bone — contrary to that in soft tissue without bone contact — hardly changes at all in terms of length and width. Taking these facts as a basis, the results reveal that the 1st shot weakened the bone. The photographic image data sets of the single shots provided proof of microfractures. One possible explanation is that the still local undisplaced constant fragments brought about by the 1st shot were most probably accelerated by the energy of the second shot and were caused to move with high energy through the tissue. One explanation for this could be that the energy of the second shot is not needed for fracture formation but serves the sole purpose of accelerating the bone fragments. This explains why the destruction pattern in this case is much more extensive than with the single shot. We were not in a position in this study to prove that the bone fragments are responsible for this because no dynamic recording was performed of the procedures during the firing process. Firing with a semi-jacketed bullet reveals an entirely different picture. No primary bullet path can be identified. Immediately after the bullet has entered, the temporary wound cavity begins. The bullet already fragmented and deformed shortly after entry. The diameter of the wound cavity is therefore much bigger than it is with a single shot fired with a full metal jacket bullet. The comparatively negligible alteration of the bullet path by the two-shot technique as opposed to the experience with full metal jacket bullets can presumably be explained by the fact that the single shot fired with a semi-jacketed bullet already resulted in such a large bullet path that the 2nd shot did not bring about any major change In order to confirm this theory, dynamic images would be desirable.
Two shots fired with a full metal jacket bullet in quick succession causes a destruction pattern that is comparable in terms of magnitude to that caused by a semi-jacketed bullet. With the two-shot technique, a large number of fractures can be expected circularly around the bullet path. Many loose bone fragments can be detected along the bullet path. The extent of the destruction is significantly greater than is the case with a gunshot wound inflicted by a single shot fired with a full metal jacket bullet. The basis for this study is the use of the two-shot technique in military conflicts. The results, however, are not only used in military conflicts. Knowledge about the kinematic effects of gunshot wounds is becoming increasingly significant in non-military contexts as well. The communal rescue service is showing an interest in the unique injury patterns that are caused by gunshot injuries. These results are contributive in this context [Table 2].
Source of Support: Nil.
Conflict of Interest: None declared.