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Killin' Science And Bullet Selection For The Layman

Killiní Science And Bullet Selection For The Layman


By "TresMon" ( 'net name) Tres Monceret

A fun but educational look at terminal ballistic science.

[I received the following question in e-mail and it turn it sparked an article. Around here "articles happen. "]

"Out of curiosity, how can a game warden tell if a deer was shot with a
muzzleloader or a rifle?"

Well, besides the obvious that anybody would know - the entry wound size and shape - it's forensics. A low velocity big bullet is more of a mauler internally; it's just brute force mashing its way through the meat. A high velocity rifle bullet kills more actually by hydraulics than by hemorrhaging (blood loss/circulatory damage.) Most modern hunters know that "energy kills," that is, energy is the biggest, baddest killer. They just don't know how to explain it.

All animals are mostly water. So think of this. Imagine hanging up a waterproof full sized punching bag thatís full of three day old mash taters. You know the ones that have increased their viscosity some. Now shoot a scalpel through it. What did we observe? The bag did not move or swing much. It was not a dramatic looking event. We have a hole through both sides of our bag that is leaking pretty fast. And if we were to dissect the bag and mash taters we would see merely slits through the wound "channel". But the "hole" or wound channel is tight, meaning from the elasticity of the mash taters "meat," the channel drew back up on itself, not 100%, but mostly.

There's your broadhead, spear and Atlatl killed deer. (Yes, spearing is STILL legal and actually STILL done in a few states. A few of my hardcore wilderness survival friends do it.) This is death by hemorrhage alone, or bleeding out, internally and a little externally. Sure, the deer experienced some energy, but no more than a major league batter getting beamed in the shoulder by a fast pitch. Not enough to kill or long term injure.

So now let's move to big bore pistols and muzzle loaders. So we shoot our hanging tater bag with a .357 mag, .41 magnum, .44 magnum, etc., or a front stuffer. Now we have energy doing some amount more of the killing than hemorrhage. And we have not just a wound channel now but also a wound cavity. What did we observe? The front of the bag was displaced or caved in a good bit from the energy. The whole bag is swinging some back and forth. We have a small hole all the way through our bag that did not seal back up. This is our wound channel. But the front side of the hole or entry side is where our channel is larger than bullet diameter and it slowly tapers down as we move deeper through the channel. This is the PERMANENT wound cavity. To explain temporary and permanent wound channel, I need to explain the hydraulic effect of a bullet.

The hydraulic effect of a bullet hitting the watery meat and core of an animal: Newton's law says, "Reckon for every tough lick thar's a equal and opposite nuther tough lick." So we observed in our front stuffer shot on the bag, the surface of the bag was displaced. Thatís energy from the bullet being dispersed into our target. So letís say we were shooting a .451" 45 cal. slug. If we shot a basically 1/2" piece of metal at the tater sack, how come the displacement on the surface was so much larger in diameter than the slug? Energy! Energy does amazing things.

Enter the temporary wound cavity. When a moderate to very high energy round enters our taters (meat/flesh), the energy damages and destroys tissue far larger than the bullet diameter. Initially energy from the bullet "blows" a quite large cavity or space in the tissue. But it does not stay this size of a space. The immediate size of the empty space or cavity is called the temporary cavity. From the amazing engineering God designed into flesh, due to the elasticity of the flesh, it will attempt to shrink back down and come back together. So this big hole or cavity we blew into the near side of our tater sack will immediately begin to shrink. And again we learned this is a temporary cavity. But we transferred such a large amount of energy into the flesh that we destroyed much of it. Due to this, though, it will shrink back down a good bit. It will not shrink all the way back down to the actual bullet diameter hole the bullet drilled into the meat. This is called the PERMANENT wound cavity. Here's a pretty good example of a temporary, permanent wound cavity and wound channel: [I'm referring to wound "channel" as the small bullet diameter hole that goes beyond the cavities.]

So why does the permanent cavity exist far larger than the actual diameter of the bullet that created it? Why does the temporary cavity not shrink all the way to the physical bullet diameter that passed through? Well we already said because the immediate tissue was destroyed but letís take a closer look. We'll recap for a second.

We shot a scalpel through our 100 lb. mashed tater filled punching bag. We ended up with a snug little leaking hole. This will kill the tater bag, but slower, and it certainly will not be dramatic.

We shot our bag with a front stuffer. Cool. For a split second we caved in the front of the bag. The whole bag is swinging. More cool. Now we got a little bitty "junior sized" football shaped hole in the near side of the bag of taters and a 1/2" hole all the way through. Way cool.

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