Killin Science and Bullet Selection for the Layman

Killin' Science and bullet selection for the layman

A fun but educational look at terminal ballistic science
by “TresMon” Tres Monceret

How can a game warden tell whether a deer was shot with a muzzleloader or a rifle?

Well besides the obvious anybody would know- the entry wound size & shape- it's forensics. A low velocity big bullet is more of a mauler internally; it's just kind brute force mashing its way through the meat. A high velocity rifle bullet kills more actually by hydraulics than hemorrhage (blood loss/circulatory damage.) Most modern hunter knows 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 a water proof full sized punching bag up outside that's full of 3 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/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 M.Taters "meat" the channel drew back up on itself, not 100% but mostly.

There's your broad head,spear & Atlatl killed deer. (Yes spearing is STILL legal and actually STILL done in a few states. A few of my hard core wilderness survival friends do it.) This is death by hemorrhage alone, or bleeding out, internally & 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 & muzzle loaders. So we shoot our hanging tater bag with a .357mag, .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 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 & 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 a animal: Newton's law says "reckin for every tough lick thar's a equal & opposite nuther tough lick." So we observed in our Front Stuffer shot on the bag the surface of the bag was displaced. Thats energy from the bullet being dispersed into our target. So lets 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 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.]
Bullet Entry

So why does the permanent cavity exist far larger than the actual diameter of the bullet that created it? Why does the Temp. 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 lets 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" foot ball shaped hole in the near side of the bag/taters and a 1/2" hole all the way through. Way cool.

Now let's shoot our tater bag deer simulator with an American favorite: the .270 Winchester. If we could see the hit in slow motion we would see the waves of energy rippling the surface of the bag. It literally look's like the concentric rings coming from a stone dropped in still water. We significantly displaced the surface of our tater sack. It's swinging pretty good overall. We go examine and see we have a full sized+ football shape "wound cavity" in the near side of tater sack and a bullet diameter hole the rest of the way through.

[cavity dimensions and "football size" references are not literal, nor dimensionally accurate nor have I ever shot “mashed taters.” They are merely used to illustrate to the readers mind familiar mediums and sizing/shapes, while conveying whats happening on/in target accurately overall. It's hard to draw a series of pictures in a readers mind, but in doing so with these familiar shapes/references I feel I have transferred the actual science and ongoings to the reader accurately.]

So what is happening in that instant the bullet transfers energy into the medium? That's the hydraulics we were talking about. Essentially a violent water column radiating out from the bullet entry point. From scalpel to bullet "energy wand":

So the scalpel made no real cavities at all. Our high velocity rifle round made a serious temporary and permanent wound cavity. So let me illustrate what this hydraulic water column does. Back to our hanging 100lb. mashed tater filled punching bag. This time we hang our tater sack in the bay of the high pressure car wash. We again are armed with our .270 Win but let's dump out our taters and fill our bag with well cooked green peas. These green peas represent cells. The individual cells tissue is made of. When we introduce energy into tissue from a blow the water contained goes the equal & opposite direction, vilonetly! Think of if we dropped $1.50 into the slot to activate the high pressure sprayer of the car wash. We stick the wand down into the peas and pull the trigger. What happens? The water pressure basically makes the immediate peas seemingly vanish, the closest mangle and the furthest effected by the water burst and leak.

Thats a good verbal picture of what is happening to tissue when massive amounts of energy are transferred from a bullet to flesh due to hydraulic energy forces, and it's quite understandable that as amazing as bodies are- some tissue, i.e. the permanent wound cavity does not recover. So thus is the ways we actually kill targets. So what do we do wit this information? We wish we our military could shoot terrorists with expanding hunting type bullets! We can use our new found knowledge of energy transfer from bullets to mash taters to better select the weight and style of bullet we shoot. Bullet selection all depends the on the average size, weight and range of the mash tater sack we are hunting. You see there are three schools of thought with hunters. The first is the antiquated and Neanderthal thought: "make the biggest "hole" [wound CHANNEL] you can -all the way through the animal to produce maximum amount of (blood) leakage."

And the second sounds so clean, sterile & harmless on the printed page: -Transfer all the energy.-

Sounds ho-hum,boring.(But it’s incredibly devastating & violent!!!)
The third school got high in the bathroom and don’t care.
They just like to hunt.

Think of this. A bullet moves because energy has been imparted to and into it. Once it leaves the bore pressure is relieved from the firing system and the bullet got what it gets and is now leaking energy slowly to the really low viscosity water we shoot through called air. If you ever have a conversation with a bullet it will refer to same as drag. If it runs out of energy it would stop forward motion in place, spent. (If there were no gravity.) There! You get it! Wait, you look uncertain. I'll give it to you: you want the bullet to stop. IN the target. Why? Transfer. Energy transfer. 100% wicked violent energy transfer. You see if your bullet regardless of caliber, diameter, weight or speed passes through the target and travels beyond, it did not give you it's all. Any energy the bullet had to travel beyond our tater sack was wasted, we could have dumped that left over energy into the mashed taters as well for even more/bigger car wash wand effect!!

So there it is- with a high velocity high energy round we want a complete energy dump into our wild free range 12 tined Tater Sac we so carefully stalked. Thats why there are so many bullets to choose from for a given caliber. Enter bullet (a.) design & (b.) weight...

Real world example. I know a well meaning green horn who was new to shooting, new to rifles and new to hunting. He went on a coyote sized furry predatorial tater sack hunt with a friend and was hooked. So he decides he needs a good rifle, camo and a few calls. Talking about his new love on the job a co-worker offered to sell him a like new ultralight weight 300 Win Mag complete with scope, for a incredibly low price. "Because it will kick yur teeth out the guy said." So our young green horn figured 1. "He could take it" and two all that power would for sure blast a dog sized fur covered flea infested mange pocked Mashed Tater Sack into the next Siriometer or so. He took the rifle.

So Mr. G. Horn went and bought some 300WM ammo, on sale. Winchester 180 grain Power Point factory loads. A real world MOOSE load. (He did not do the math I'm sure, I'll do it for him: 3500 ft. lbs. of car wash wand effect at the muzzle.) Looking at the big shiney menacing ammo I'm sure Mr. Horn was sure it would blast the doggish creature for at least a siriometer!!

So after a while he calls me. “Man this thing really-REALLY kicks!” I chuckled having been there done that in my youth. I threaded his barrel and installed a nice muzzle break. He was really happy with the recoil reduction and off he went. Soon enough he made his first “I got one!” phone call to a buddy. But he was quick to tell me the critter just limped about 20 paces and died. No siriometer. I chuckled having been there and done that in my youth and explained bullet selection.

You see had if Mr. Horn had hand loaded him some little bitty 110 grain Sierra hollow points at a anemic (for the Win Mag with this bullet) 3200 fps, he would have opened up that critter like a book displaying it’s most every deep and inner thing, literally. True the little bullet would had a good bit less energy: 3200 lbs. But it would given Mr. G. Horn it’s all! The little bullet would have disintegrated in the critter for a 100% energy dump, where as the Moose bullet that was actually used likely zipped right through with no “upset” commonly called expansion or mushrooming on behalf of the bullet in the 35 lb. target. After all that load was designed to hold together, burrow deep and energy dump in a dangerous big boned hardy built massive Tater Sac weighing upwards of 1700 pounds for the Alaskan-Yukon variety.

Speaking of bullet upset, their is fascinating engineering that goes into bullet design. You see that dumb piece of metal we call “bullet” has no intelligence nor on board computer but must juggle the depth-ofpenetration/ energy dump act to perform it’s best. And to compound this complexity it must do it anywhere in an extreme velocity spread. If we shoot our massive moose tater sack and the bullet disintegrates on the shoulder muscle we have wounded him, he’ll run off and we may have lost him and wasted the meat & and if he succumbs to the wound the life. If it zips through him without hitting a vital organ we again have wounded him and likely lost and wasted him. Enter bullet engineering. A bullet upsets and begins to expand. This ever increasing blunt frontal diameter increase increases the difficulty for the bullet to penetrate. This rate of expansion must be carefully controlled through inherent design to allow the bullet to expand slow enough so it can burrow 1. deep enough to get past the near side muscle and into the vital organs but 2. fast enough to not completely pass through the animal thereby wasting energy. That would be a feat of engineering if the bullet hit the mash tater sac at the same speed every time. But it’s always impacting at differing speeds. If we engage our 1700 pound marsh wading mashed tater sac at 220 yards the bullet will impact at far greater velocity than it will if fired from a long range hunter engaging our swamp tater at 1106 yards. Either way, the bullet must not under or over expand to penetrate sufficiently and energy dump. And amazingly they get It right most of the time!

In conclusion bigger is not always better in regards to quick, clean ethical kills wether the subject of discussion be “which cartridge” or “which bullet.”

Regards,
“TresMon”

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