Archive | December 2015

Ballistic info

Ballistic info can be found here.

http://brassfetcher.com/

Why I’d Rather Be Shot With an AK-47 Than an M4

Note: An important rule in a gun fight;  Avoid getting shot!

December 19, 2015

Why I’d Rather Be Shot With an AK-47 Than an M4

Admittedly, I’d rather not be shot with either, but if I had to choose, I’d take a round from the AK-47 over the M4 any day of the week. To add a caveat to that statement, I’m talking from relatively close range here—say up to 150-200 meters.

To understand why, it’s important to first take a very basic look at the physics behind terminal ballistics. In this case, consider the science of what happens when a penetrating missile enters a human body. The first place to start is the following kinetic-energy equation:

KE = ½ M (V1-V2)2

Breaking this equation down into its components, we have kinetic energy (KE) influenced by the mass (M) of the penetrating missile, as well as the velocity (V) of the missile. This makes sense; it is logical that a heavier, faster missile is going to do more damage than a lighter, slower missile. What is important to understand is the relative influence that mass and velocity have on kinetic energy, as this is key to understanding why I’d rather be shot with an AK than with an M4. You’ll notice that the mass component of the KE equation is halved, whereas the velocity component is squared. For this reason, it is the velocity of the projectile that has far more bearing on the energy that it delivers into the target than the mass.

The V1-V2 component of the equation takes into consideration that the projectile might actually pass straight through the target, rather than coming to rest in the target. In this instance, the change in the velocity of the projectile as it passes through the target (V1 being its velocity as it enters, and V2 being velocity on exit) is the factor that is considered when calculating how much energy the missile delivered into the target. Naturally, if the projectile comes to rest in the target (ie: no exit wound), then V2 equals zero and the projectile’s velocity as it entered (V1) is used to calculate the KE.

That’s enough physics for now, but you get the concept that the optimum projectile to shoot someone with is one that has a decent mass; is very, very fast; and is guaranteed to come to rest in your target so as to dissipate as much energy as possible into them, and hence do maximal damage.

The next concept to grasp is that of permanent cavitation versus temporary cavitation. Permanent cavitation is the hole left in a target from a projectile punching through it. You can think of it simply like a sharp stick being pushed through a target and leaving a hole the diameter of the stick. The permanent cavity left by a bullet is proportionate to the surface area of the bullet as it passes through the tissue. For instance, if an AK-47 round of 7.62mm diameter at its widest point passes cleanly through a target, it will leave a round, 7.62mm permanent cavity.

If this hole goes through a vital structure in the body, then the wound can be fatal. However, if the bullet passes through soft tissues only, the permanent cavity can be relatively benign. This is a slight oversimplification of the concept, as bullets will rarely remain dead straight as they pass through human bodies; they have a tendency to destabilize, and for the heavier back end of the bullet to want to overtake the front. This concept, known as yaw, increases the frontal surface area of the bullet as it passes through tissue, and hence creates a larger permanent cavity.

Far more damaging than the permanent cavity left by a projectile is the temporary cavity that it creates. Anyone who has watched the TV show MythBusters will have some familiarity with this concept, and it is best demonstrated using slow-motion video imagery of bullets being shot into special jelly known as ballistic gelatin, which is calibrated to be the same density as human soft tissues. What can be seen in these video images is the pulsating dissipation of energy that emanates out from a bullet as it passes through the gelatin. This is a visual illustration of the concept of temporary cavitation, and it allows the viewer to begin to appreciate the devastating effect that a high-velocity missile can have once it enters a human body.

The temporary cavitation is the transfer of kinetic energy from the projectile into the tissues of the target, and as we learned above, is relative to the mass and, more importantly, the velocity of the projectile. As the energy of the projectile is dissipated into the tissues of the target, the temporary cavitation pulverizes structures adjacent to the bullet’s path, including blood vessels, nerves, muscles, and any solid organs that may be in close proximity. For that reason, the high-velocity projectile does not need to pass directly through a structure in the body to destroy it. The higher the kinetic energy of the projectile, the further out from the permanent cavity the temporary cavity extends.

Below is a slow-motion video by Brass Fetcher of a 5.56x45mm round (same as what the M4 fires) hitting ballistic gelatin in slow motion. After watching, the medical provider can begin to appreciate the damage done to tissues by the pressure wave of the temporary cavitation.

Having had the chance to treat dozens of high-velocity missile wounds over my years in the military, I’ve seen firsthand the effect that various rifle calibers can have at various distances, hitting various body parts. Naturally there are a multitude of variables that come into play when someone gets shot, and no two gunshot wounds are ever going to be the same. The purpose of this article is not to draw any academic conclusions about the ballistics of the AK-47 versus the M4, or argue the merits of one ammo over another, it is to introduce the concepts of the different wounding profiles of permanent and temporary cavities using a couple of case studies.

Below are two examples I was involved with that illustrate somewhat of a comparative study of an AK-47 round and an M4 round striking approximately the same anatomical location, and from roughly the same range (in these cases, 150-200 meters).

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This series of photos you can see a particularly nasty M4 gunshot wound, with a small entrance wound in the right lower buttock, and a massive exit wound in the right lateral thigh. The X-ray in the last image shows that the projectile struck the upper femur and demolished the bone, sending secondary bone fragments flying through the tissues and accounting for the majority of the exit wound. The damage done by the pressure wave of the temporary cavity can be appreciated in the first image, with deep bruising extending up the buttock and into the casualty’s lower back. This bruising resulted from the energy dissipated through the tissues pulverizing small blood vessels in its path (think back to the ballistic gelatin video to imagine what went on in the tissues).

The granular material in the middle of the thigh wound seen on the X-ray is an older-generation QuikClot advanced clotting sponge (ACS), which was inserted at the point of injury for hemorrhage control to excellent effect. The bright white fragments on the X-ray are small pieces of the bullet, which had disintegrated on impact with the tissue and bone. This is another characteristic of the M4 round that makes it all the more unappealing to be shot with—the tendency for the bullet to disintegrate if it strikes tissue at a decent velocity.

Despite being a jacketed round, because it’s smaller, lighter, and faster than an AK-47 projectile, the 5.56mm tends to yaw faster once it hits tissue. The shearing forces on the bullet once it is traveling at 90° through the tissue often tears the bullet into pieces, thus creating multiple smaller projectiles and increasing the chances of all of the bullet parts remaining in the target, and hence dissipating more energy. The AK-47 round, being slightly heavier and slower than the M4 round, has a tendency to remain intact as it strikes tissue, and although it will penetrate deeper, it tends to remain intact and not yaw until it has penetrated much deeper than the M4.

Here’s a video from The Ammo Channel of the AK-47’s 7.62x39mm projectile being fired into ballistic gelatin for comparison to the video above of the 5.56x45mm (M4) round. Although the video shows a soft-point round being used, which theoretically should be more destructive than its full metal jacket counterpart, the video still illustrates nicely the significant penetration of the AK-47 round without it yawing significantly or disintegrating.

I once saw a good case study illustrating this point, where a casualty had sustained an AK-47 gunshot wound to the right lateral thigh and we recovered the intact bullet from the inside of his left upper abdominal wall. It had passed through approximately one metre of his tissues and shredded his small bowel, but the projectile hadn’t fragmented at all, and the temporary cavitation hadn’t done enough damage to be lethal. The casualty required a laparotomy to remove multiple sections of small intestine, but he made a good recovery. That one is a story for another time.

The next photo is of a good friend of mine who was shot by an AK-47 from approximately 200 meters while standing right next to me! Fortunately the bullet passed cleanly through, and after a surgical clean-out the afternoon of the injury, he turned up ready for work the very next day. They breed them tough where he is from!

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This image was taken a few days after the injury and the bruising from the temporary cavity of the projectile can be seen along the path of the bullet. The entrance wound is at the top of the left buttock, with the exit being down on the left upper thigh. Although an unpleasant injury to have, the fact that the AK-47 round was traveling slower than an M4’s round at the same range would have been, coupled with the fact that the projectile remained intact and didn’t yaw significantly as it passed through him, meant the wound was nowhere near as devastating as the above-mentioned M4 injury in the same area. It must be noted, however, that the comparison is far from perfect given that the M4 injury involved the bone, with the one immediately above passing solely through soft tissues.

So there it is. All things being equal, when all is said and done, I’d rather be shot with an AK-47 than a M4 on any day of the week. Naturally, as medical responders, it is always important to treat the wound and not the rifle that inflicted it, and I have certainly seen some horrendous AK-47 wounds over the years and some relatively minor ones from M4s. It all depends. The main take-home points for first responders and medicos are: Be aware of the magnitude of damage that can be caused by the temporary cavitation resulting from high-velocity missile wounds, and if you find an entrance wound, there’s no telling where in the body the projectile might have ended up!

Thanks for reading! Comments and questions are welcome. Cheers.

Neck Shot from an 7.62 X 39 AK47!

An AK-47 Bullet Through the Neck Couldn’t Stop Him!

The following case study is of a friend of mine (written with his permission) who was shot through the neck by an AK-47 during an operation from a range of about 150 meters. The bullet entered the back of his neck just right of the midline and then blew out the front of the left side of his neck. Remarkably, he not only survived, but has subsequently made a near-complete recovery, and has conquered both the North and South Poles on foot! This case study is fascinating from both a terminal ballistics perspective, as well as from a medical perspective regarding the immediate and delayed effects of the temporary cavitation, or pressure wave, emanating from the high-velocity bullet as it passed through his neck.

Those of you who have read my previous article on why I’d rather be shot by an AK-47 than a M4 will already understand the concept of permanent versus temporary cavitation, and the basics of the theoretical differences in wounding profiles between the AK-47 and the M4. I think it’s worth a read. The key concept from that article that relates to the current case study is the tendency for an AK-47 round to remain intact and generally plough straight through short distances of human tissue before it destabilises and starts to yaw, or tumble. Should the bullet not hit any bone, the result is often a nice clean through-and-through wound, which is exactly the instance in the current case study.

In that setting, assuming the bullet hasn’t passed through any vital structures, the permanent cavity left by the bullet is akin to sticking a sharp stick through the casualty. This brings me to my first set of images, which show the neat hole punched through the casualty’s neck. The first image was taken on the day of the injury, with the remainder of the images taken the day after the incident, and illustrating the near perfectly circular exit wound of the bullet, only slightly larger than its 7.62mm diameter. The bullet had traversed approximately 15 cm (six inches) of tissue, and I suspect if the round had been from a M4, the outcome may have been dramatically worse (once again, covered in my previous article).

AK47 Neck Wound
An AK-47 Bullet Through the Neck Couldn't Stop Him!
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Even more interesting than the images above are the CT images depicting the path of the bullet through the casualty’s neck.AK47-CT-scan-1

I’m by no means an expert at interpreting CT scans, but as a basic orientation to these images, we are looking at a slice through the casualty’s neck at the level where the bullet passed through. As can be seen in the initial images, this is at the level of his mouth and tongue. When looking at a CT slice, it is as though you are looking up from the feet of the patient, so what you see on the right of the image is actually the patient’s left. The first thing to appreciate is the swelling caused by the trauma of the bullet causing the tissues on the left side of the casualty’s neck (right side of the image) to bulge out when compared to the other side.

The white part at the center of the image is the vertebra at that level, with the dark semi-circular structure at the center of it being the spinal cord. The medically initiated will pick up on the fact that a small chip of bone has been taken off the back of the vertebra, or the spinous process. So in effect, the casualty had a broken neck, which has implications for the first responder in moving him around during his management and evacuation. As we’re all taught, if a spinal injury is suspected, the casualty should be kept as still as possible in case the injury is unstable and movement could damage the spinal cord, potentially causing paralysis.

This approach is fine for most civilian contexts, however in examples such as this one where there was an ongoing tactical situation, the priority is always to reduce the threat and move the casualty to a safe location immediately, with minimal regard for spinal precautions. While there is always a possibility of an unstable cervical spine injury following penetrating trauma, it is generally accepted that the risk is very low (<1 percent) (Lustenberger et al.  2011). Furthermore, even if the cervical spine is unstable following a gunshot wound, the spinal cord can still remain perfectly intact (Apfelbaum & Waldman 2000).

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These next images show the path of the bullet through the neck, and the vital structures that the bullet somehow didn’t disrupt. Also included is an anatomy slide taken from the Internet, showing the gross structures at roughly the same level for comparison. In the first image, the path of the bullet can be seen by the small pockets of air drawn into the tissues as the bullet passed through, which appear black on the CT image. A blue line has been drawn along the bullet’s rough path to illustrate. The next image was taken after a dye was injected in the casualty’s veins, which pumped around his blood vessels, causing them to appear white on the CT scan.

Mentally superimposing the path of the bullet, it can be seen that it passes directly through a rather large pipe in the front of the casualty’s neck, which I assess as being the internal jugular vein. (I’m very happy to be corrected by any radiologists out there!) Immediately next to the internal jugular vein is an even more important structure, the internal carotid artery, which, had it been disrupted, would have almost certainly resulted in the death of the casualty given the circumstances on the day. Miraculously, neither of these major blood vessels were damaged, with the only rational explanation offered by the treating surgeon being that the bullet simply pushed them aside. Once again, in my opinion, were this to have been a M4 round, I suspect the outcome would have been dramatically worse.

So far I have only considered the damage done by the permanent cavity caused by the bullet, which both fractured the spinous process of the casualty’s vertebra and punched through the exact location of his major neck blood vessels without disrupting them. Of more medical significance, both on the day and ongoing since, was the damage done by the temporary cavitation of the bullet as it passed through. Those who have read my previous post (or have a good grasp of the subject) can disregard the following video, but for those who haven’t, the following YouTube video by Brass Fetcher demonstrates the pressure wave generated by a 7.62x39mm bullet when it passes through tissue. In the video, a bullet is shot into ballistic gelatin that has roughly the same density as human tissue. The pressure wave seen disrupting the gelatin in the video is caused as the bullet rapidly decelerates and transmits energy into the gelatin. The same occurs in human tissue with the pressure wave, or temporary cavity, causing damage to structures around, but not in the direct path of, the bullet.

The pressure wave emanating out from the path of the bullet through the casualty’s neck passed directly through his spinal cord. As it did so, the casualty went into a state of spinal shock, causing him to immediately lose all function of his nervous system below the injury and, while remaining conscious throughout the ordeal, making him temporarily quadriplegic. Spinal shock is often loosely referred to as a spinal concussion, similar to the temporary symptoms experienced following a knock to the head that gradually settle over a period of time. Thankfully, this was the case with the casualty in this case study, with the majority of his nervous system function returning in the hours post-injury, and a gradual recovery of almost all of his nervous functions after years of intensive rehabilitation.

Although making a steady recovery from the spinal shock in the months to years following the injury, a more insidious sequelae from the damage done by the temporary cavity of the bullet began to manifest. Interestingly from a medical perspective, the casualty developed symptoms of traumatic brain injury (TBI) which, while frequently seen in war casualties, is more typically associated with blast injuries, and almost always associated with loss of consciousness. Having spent my previous career in the military medical space, I had never heard of the concept of a TBI from a gunshot wound distal to the head. Having been introduced to the concept, however, and keeping the video image of the temporary cavitation from a high-velocity missile in mind, it makes perfect sense that that same pressure wave that disrupts tissues surrounding the permanent cavity of a bullet could cause significant damage to brain tissue, especially if shot at relatively close range through the neck or upper torso.

In fact, studies have demonstrated that ballistic wounds as distal as the abdomen and thorax can cause a transmitted pressure wave through the brain with enough force to generate a TBI (Courtney & Courtney, 2007). I encourage anyone reading this who has an interest in military medicine or TBIs to look up the Courtney reference, as it has opened my eyes to a new significant risk of TBI resulting from distal gunshot wounds that I was previously oblivious to, which has implications for early management of such injuries. With today’s heightened terrorist threat and recent world events, these military-related wounds may be presenting at a civilian emergency department near any one of us in the near future.

As stated in the introduction, fortunately this story has a happy ending in that the operator who was shot has gone from strength to strength in his recovery and is not showing any sign of slowing down. Frustratingly, despite being on the ground on the day of his injury, I was unable to get to him due to his geographical location and the tactical situation. The heroes of the day (apart from the casualty) were the first responders and the U.S. Aeromedical Evacuation team, who came into a highly complex and dangerous situation to extract the casualty under fire. TacMed Australia extends its sincere gratitude to all the pre-hospital medical practitioners and evacuation elements out there who save lives daily in civilian and military context alike.

As always, comments and questions are welcome.

References:

Apfelbaum JD, CS, Waldman N 2000, ‘Unstable cervical spine without spinal cord injury in penetrating neck trauma’, American Journal of Emergency Medicine, vol18, no. 1, pp. 55-57.

Courtney A, CM 2007, ‘Links between traumatic brain injury and ballistic pressure waves originating in the thoracic cavity and extremities’, Brain Injury, vol21, no. 7, pp. 657-662.

Lustenberger T, TP, lam L, Kobayashi L, Inaba K, Plurad D, Branco BC, Demetriades D 2011, ‘Unstable cervical spine fracture after penetrating neck injury: a rare entity in an analysis of 1,069 patients’, Journal of Trauma, vol70, no. 4, pp. 870-872.

Living Large: Feasting on Spam Canned Ham!

The Weather Outside is Frightful Spam Canned Ham is so Delightful…

 

Ingredients:

  • 1 can of Spam (Cut into Chunks.)
  • 1 can Pineapple Tidbits
  • 3-4 Tbs. Olive Oil
  • 3-4 tsp. Cooked Onions, sliced & diced (I like Vidalia Onions…)
  • 2 tsp. Red or Green Pepper sliced up.
  • ½ cup Pineapple-Apricot Jam (or Grape Jelly)
  • ½ cup Ketchup
  • 1 cup Brown or White Rice. ( I like the Brown Rice…)

Directions:

In oil, first cook the onions until soft, about 7-10 minutes on low heat, add the peppers, add the chunked ham and a can of drained pineapple tidbits. Now mix equal portions of the jam of your choice jam with the ketchup in a bowl. Stir the sauce into the frying pan that contains the ham and pineapple mix and heat low-med, stir occasionally to keep the mix from burning! When completely heated, serve over rice in a bowl.

Fighting Rifle Set-Ups

A fighting rifle needs a few basic but essential accessories.

These are:

  • A white weapon mounted flashlight. This is need for target identification in the dark at close range. You must be sure of target and what is beyond it. Once the trigger has been pressed, you cannot stop the bullet! Be sure of your target!
  • A sling: It is no secret that we like the Viking Tactics Wide Padded Two Point Sling for its versatility, but any sturdy sling will work. Sometimes you need to go hands free. A sling allows for this while retaining your weapon.
  • Iron sights that are zeroed. We prefer a 50 yard zero. (Scroll down this blog sight and read why!) We generally use iron sights as a back up sighting system to a red dot or magnified optic, but there is nothing at all wrong with using iron sights as primary sights.

That is about it.

Keep it simple.

You can watch the video below for further guidance in your quest.