Probing the path of a pernicious projectile
Knowing how a bullet works when it leaves the barrel might help you understand what to expect when it hits its target. It weighs 124 grains (about 8 grams), and it sits in the dark for weeks, months or even years. It gets jostled, shaken and bumped incessantly during that time. Depending on how it is carried, it can also accumulate a fair amount of pocket lint within its gaping maw. It is a SIG Sauer V-crown 9mm hollowpoint bullet, and it is about to earn its keep.
For such a modest, inert thing, it embodies a shocking amount of technology. The case is nickel plated for corrosion resistance, smooth feeding and long life. The powder is specially formulated for consistent performance and low flash. The primer is the best man can produce.
It is, however, in the bullet where the real magic happens. That’s the payload—the warhead, if you will—and that is the limiting reagent to the cartridge’s overall performance.
The SIG V-crown bullet is marketed as a “hollowpoint within a hollowpoint.” I didn’t really understand that very well until I saw it in action. Now, it makes perfect sense.
The lead slug nestles tightly within the jacket material, held in place by a cannelure crimped circumferentially around the bullet’s waist. This mechanical interface is what tends to keep the lead core and the jacket together during the violence that is to come. The geometry and scoring of the V-shaped snout, hence the name, give the angry end of the thing an antiseptically sinister, although utilitarian, appearance. The cone described within the nose of the contraption tapers down into a point in the center. From this apex there is another small, but intentional,
star-shaped void formed down into the core. Every miniscule snippet of the bullet’s geometry has some intentional purpose.
SIG Sauer burns through twice as much ballistic gelatin as the entire rest of the country combined. I’ve seen this up close, and it’s obscene. The V-crown bullet is the end result of a simply ridiculous amount of R&D.
SOMETHING BAD HAPPENS
It’s never expected. If you knew it were coming, you’d either avoid the situation or buy yourself a tank. However, it always seems to drop out of the clear, blue sky. In this case, it took place inside a vehicle.
Here, we will eschew the combat details in favor of physics ... with a little human anatomy tossed in for flavor.
The Glock 43 is up and out in a flash. The finger indexes from the side of the trigger guard to the
THE GEOMETRY AND SCORING OF THE V-SHAPED SNOUT, HENCE THE NAME, GIVE THE ANGRY END OF THE THING AN ANTISEPTICALLY SINISTER, ALTHOUGH UTILITARIAN, APPEARANCE.
trigger, automatically depressing the blade safety in the trigger face and rendering the system live. The index finger of the right hand exerts about 5.5 pounds of force on the appendage, further compressing the striker past its tripping point. The striker slams forward under spring pressure and vigorously dents the face of the primer.
The primer face is relatively soft and deforms readily in response to the impact of the firing pin. A small quantity of shock-sensitive primer material is compressed between the primer face and the anvil of the primer. Mechanical deformation and a subsequent rapid increase in pressure conspire to raise the temperature of the material past its flashpoint, and the stuff conflagrates. The resulting jet of hot plasma is directed through the flash hole in the base of the cartridge and ignites the powder within.
THE JOURNEY BEGINS
The powder contains its own oxidizer, so it burns independently of outside air. Underwater, outer space or sealed in a plastic bag—it doesn’t matter. This rapid reaction releases a large volume of hot, high-pressure gas. The chamber of the weapon supports the walls and base of the cartridge, so all that energy is directed against the butt of the bullet. The bullet, therefore, accelerates from 0 to about 1,100 feet per second in 3.39 inches, suffering underneath an accelerative force some 66,500 times that of gravity.
The G43’s barrel twist rate is one turn in 9.84 inches. That means the bullet spins one revolution for every 0.82 feet. At 1,100 feet per second, if my math is correct, that puts the bullet spinning at a bit north of 80,000 rpm at the muzzle.
In this particular case, the projectile travels about 3 feet and then contacts the seat cushion of a pickup truck. Spinning like a tiny 9mm hole saw, the V-crown round cuts a perfect circle in the top of the seat, bores through the intervening foam and cuts a second perfect circle through the front. It then travels about another foot before the next phase of its trek.
THE PLOT THICKENS
Our next barrier is denim. Everybody owns a
pair of blue jeans, and that is what was wrapped around this particular leg on this particular day. The bullet has not slowed appreciably, so it snips through the thin cotton cloth with the same aplomb with which it transited the truck seat. Now, things get interesting.
Skin is the largest organ in the human body. Its primary function is to separate you from the rest of the world; when intact, it does a simply splendid job of that. Skin also serves as a support matrix for untold miles of nerves and capillaries, as well as sundry other bits, such as hair and apocrine sweat glands. The delicate interplay among all that complicated stuff helps regulate your body temperature, prevents contamination, hinders infection and precipitates a delightful little endorphin boost whenever your bride brushes your arm as she walks by in the kitchen. Skin is a remarkably pliable and elastic material that is purpose-designed to resist puncture, abrasion and tearing.
It never stood a chance.
OUR BULLET GOES TO WORK
The rapidly spinning projectile cuts through the outer layer of skin as easily as it has everything else thus far and dives vigorously inside. It encounters a soft, warm, wet hydraulic medium too complicated and heterogeneous to categorize readily. Human males are about 60 percent water; females are closer to 55 percent. Because the owner of this leg is in possession of both X and Y chromosomes, that means his tissues are at the higher concentration. As a result, fluid dynamics now become the decisive factor in how our sordid, little tale unfolds.
Unlike gases, liquids are incompressible. That means pressure at one point is transmitted in real time to other contiguous fluids. It is this peculiar property that allows the pilot to manipulate the control surfaces of an airliner. It also allows you to apply the brakes to stop your car when your son’s soccer ball unexpectedly bounces across your path.
THE SIG V-CROWN BULLET IS MARKETED AS A “HOLLOWPOINT WITHIN A HOLLOWPOINT.” I DIDN’T REALLY UNDERSTAND THAT VERY WELL UNTIL I SAW IT IN ACTION.
The bullet is still travelling really fast, so this surrounding wet, gooey amalgam struggles mightily yet fails to get out of the way. The subsequent hydraulic pressure exerts a truly immense force against the interior of the V-crown’s hollowpoint cavity. This force drives the lead core to mechanically deform outward against the jacket material, fracturing at its predetermined failure points such that the various components of the bullet now expand outward like the petals of a flower.
These expanding petals hugely increase the surface area of the transiting bullet, magnifying the mechanical braking force and spilling energy into what is rapidly becoming a bloody great mess. The bullet yaws a bit, ripping and tearing as its linear and rotational velocities decrease violently.
In this particular case, the bullet tore through muscle, fascia and sundry goo without striking bone, nerves or plumbing of consequence. That’s the amazing power of randomness: It’s always better to be
THE BULLET, THEREFORE, ACCELERATES FROM 0 TO ABOUT 1,100 FEET PER SECOND IN 3.39 INCHES, SUFFERING UNDERNEATH AN ACCELERATIVE FORCE SOME 66,500 TIMES THAT OF GRAVITY.
lucky than good.
The bullet has torn completely through this human calf in a millisecond and now tents against the skin on the far side. This time, the device is fully deployed and much slower but still spinning like a jagged metal dervish. It carves through the skin from the inside like a table saw through a hot dog. Unlike its entry, its exit is thoroughly devoid of elegance: Where the entrance wound was a relatively cute, little 9mm hole, the exit is jagged and closer to 4 inches.
Much spent, the fully deployed bullet now zips across the cab of the truck and lodges in the facing door, denting the steel deeply enough to secure the now-weary projectile in place.
WHERE THE ENTRANCE WOUND WAS A RELATIVELY CUTE, LITTLE 9MM HOLE, THE EXIT IS JAGGED AND CLOSER TO 4 INCHES.
THE IMMEDIATE AFTERMATH
The subject of this dark, little physics experiment was fairly fit and healthy. He told me the initial impact felt like being hit with a baseball bat. He had maybe a 30-second grace period after the bullet’s initial impact. During that time, he could have moved, thought and fought—as long as he didn’t try to put weight on the injured limb. After the 30-second mark, however, he was done.
Up to that point, the entire event had been traumatic but relatively painless. After that moment, the pain became exquisite and debilitating. The wound also began to bleed with vigor. The immediate application of direct pressure kept things from going truly sideways.
THE REST OF THE STORY
The ER staff cleaned and irrigated the wound and then closed it with a combination of sutures and surgical staples. Owing to the bullet’s fortuitous track, nothing about the event was immediately life-threatening. However, the pain did not abate, and the surrounding flesh grew red and angry. Nearly a week later, the surgical team opened the offended leg back up to take a peek inside.
The culprits were actually an odd amalgam: Within the cavernous defect were found two hole-cutter bits of Naugahyde, a little cylinder of foam rubber and a scrap of denim. Naugahyde is an artificial leather substitute used in the manufacture of automobile seats. It consists of a knit fabric backing surrounded by a polyvinyl chloride plastic coating. In its natural state, the stuff is also awash in opportunistic microorganisms.
It seems the transiting bullet picked up these four bits as passengers, transported them into the leg parenchyma and then deposited them there before continuing on its trek. Once the offending objects were removed and the wound was vigorously scrubbed, everything healed up nicely, albeit with a little help from some aggressive antibiotic therapy.
There are lessons aplenty to be derived from this sordid episode. For starters, these are not your granddad’s FMJ bullets. High-tech rounds such as the SIG V-crown are hugely more efficient than their predecessors of even a single generation prior.
This was a peripheral shot, and it was thoroughly effective at expeditiously taking the fight out of a determined combatant. Had the same bullet wrought its mischief among critical organs, the ending would not have been nearly so bonny.
Pack the biggest gun you can comfortably pack, along with the best defensive ammo you can afford. If ever called upon to serve for real, expect these remarkable Information Age bullets to give their lives enthusiastically for the cause. Do your part, and they should reliably do theirs.
Right: The SIG V-crown bullet is described as a “hollowpoint within a hollowpoint.” The secondary star-shaped void is visible at the apex of the bullet’s mouth. Below: We spend untold hours on the range practicing with our defensive handguns. The...
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Above: The exit wound was closer to 4 inches, ripping roughly along the long axis of the limb. Left: The entrance wound was a relatively tidy defect not much larger than the 9mm bullet diameter. Entrance wounds frequently belie the mischief that lurks...