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Old July 5, 2007, 02:27 PM   #1
TNBulldog
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Bullet weight vs energy

Can someone explain to me how bullet weight vs energy is relevant in practical hunting application? I understand a heavier more solid bullet with less tendency to disform will penetrate better than a light bullet designed to expand moving faster will.

What I don't understand is how surrendering energy in the process helps. For instance, my Cor-Bons fired from my 454 are 335 hard cast heads with 1,904 foot pounds at muzzle. I've seen a 410 grain from a different manufacturer that is also hard cast but only produces 1,720lbs. Likewise, on the Garrett site there are some heavier 45-70 bullets (500gn) producing less lbs (300lbs) than lighter ones (400+/-gn).

Once you get up to a certain bullet weight don't you want the extra energy as oppossed to wieght? How does the exta weight help you any more? Does the relatively lighter bullet disform THAT much more to justify the considerable loss of energy? I can see 240gn compare to 335gn in a 454, but 335 to 410? Do you really need the weight instead of the energy?

Can someone explain this to me?
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Old July 5, 2007, 03:31 PM   #2
Scorch
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The long answer is-
You calculate the energy any load has the same way-
1/2 the bullet weight in pounds X velocity squared
divide by
32 (acceleration of gravity)
This formula gives a number in foot-pounds of energy.

Lighter, faster bullets generally win in this situation, since velocity is squared.

But there is also
Weight x velocity = momentum
where heavier bullets win due to the fact that they are harder to stop and therefore penetrate more.

There are 2 variables: bullet weight and velocity, SO . . .

If the bullet weight is higher at the same velocity, energy will be higher.
If the bullet weight is higher at lower velocity, energy can be lower or higher, depending on velocity.
If the bullet weight is lower at the same velocity, energy will be lower.
If the bullet weight is lower at the same velocity, energy will be lower.

So, the short answer to your question is that the second load is traveling a lot slower than the first load, therefore has less energy.
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Old July 5, 2007, 04:32 PM   #3
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So really energy is only one way of looking at it and isn't telling the whole story essentially?
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Old July 5, 2007, 08:18 PM   #4
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Basically yes.

There are a number of "formula's" that are used to determine how effective a round might be. Straight up kinetic energy is the popular one of the day. A popular one around the turn of the 19th century was the Taylor Knock Out (TKO) formula. It was basically weight of bullet in lbs * velocity * bullet caliber.

Take for instance a .375-magnum rifle shooting a 300-grain bullet at a velocity of 2560 fps times caliber of .375. This equals a TKO index of 41. Contrast this with a .50 muzzleloading rifle shooting a 600 grain maxi, at a velocity of 1400 fps times caliber of .50. This produces an index of ~56.

Which is better? Who knows!

Personally I've found that given two loads with the same kinetic energy, the one with a heavier slower bullet of better sectional density penetrates farther.
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Old July 5, 2007, 09:47 PM   #5
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One More Thing

Kinetic energy doesn't kill anything!
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Old July 5, 2007, 11:45 PM   #6
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Kinetic energy doesnt kill anything... but speed and well placed shots do.

I am a fan of the smaller faster bullet as opposed to the larger heavier and therefore slower bullet.
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Old July 6, 2007, 12:35 AM   #7
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With the Garrett 45-70 rounds, the 420 grain has a .33 inch meplat while the 540 grain has a .36 inch meplat...which basically hits harder despite having less energy. Plus the 540 grainer is going to retain a higher percentage of its velocity (and therefore energy as well) as it goes farther downrange. Does that help?
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Old July 6, 2007, 08:34 AM   #8
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For a slow moving projectile, the larger diameter makes a larger hole, although adjacent tissue damage isn't very large. The heavier weight means through-and-through penetration, generally, allowing for faster bleed-out. A large meplat helps in creating more tissue damage, compared to a round nose.

The lighter, expanding bullets of high velocity do a large amount of tissue damage. The release of energy in soft tissue can create what I call a double-handful of mush; some bullets even exit a cross-body shot after doing this.

I guess one way to put it would be that no single factor is THE answer. It's a combination of velocity, bullet weight, and bullet construction--plus some thought and then some experience.

Art
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Old July 6, 2007, 06:09 PM   #9
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a semi-truck hits a small house at 30 miles per hour, and a Ford pick-up hits a similar house at 60 miles per hour, which does the most damage?

The semi will bash the hell out of the house and end up parked in the living room.

The pick-up will blast it's way thru the house and out the back wall.

Do you want a hole clean thru or do you want to destroy everything in the front two rooms?

Either way, the house is down for the count.

Faster + Smaller = shock and penetration if it holds together.

Slower and heavier = Shock, more destruction and less penetration.

I am a simple kinda guy. I need terms I can understand.
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Old July 6, 2007, 07:19 PM   #10
roy reali
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Re:desertfox

You need to check out the Box of Truth website. Only one cartridge went all the way through his contraption. It was the .45-70. Hardly a small and fast projectile.
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Old July 8, 2007, 03:23 PM   #11
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Hydrostatic shock is what generates the so called "knock down power" in most deer sized creatures...I say that because when you are talking about dangerous, heavy hided game, you really need the deep, deep bone crushing penetration...so keeping this discussion to that I'll explain - the shock waive that creates tissue damage is a product of the velocity and bullet design. Bullets designed to open up create more hydrostatic shock than those that don't. Hence a 300 gr. solid bullet hitting a deer at say 2000 fps will blow through the animal, but create less TISSUE DAMAGE than a 25 or 27 cal. hitting the same deer at 3000 fps. However, due to the lack of inertia on the smaller bullet, you may or may not get an exit wound, but there is 100% probability that you will get the exit with the 300 gr. bullet. However, the hydrostic shock damage of the faster bullet will create more internal damage by the energy being distributed over a greater area through shrapnel and so forth. What it all boils down to is proper calliber AND bullet Selection for the game being hunted.
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Old July 8, 2007, 06:49 PM   #12
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Quote:
Faster + Smaller = shock and penetration if it holds together.
Slower and heavier = Shock, more destruction and less penetration.
Actually, that is almost exactly backwards. Slow, heavy projectiles penetrate farther than light, fast ones. A semi hitting a house at 30 mph (to use the example posted) would be down the road a ways before it could be stopped. A pickup at 60 mph will stop inside the house.

Which is better? The fast/light bullet delivers all its kinetic energy and kills the animal. The slow/heavy bullet delivers part of its kinetic and kills the animal. Either way, it's dinner time.
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Old July 13, 2007, 03:18 AM   #13
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Thanks for clearing that up for me. Like I said, I need it in terms I can understand.
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Old July 13, 2007, 04:46 AM   #14
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The affect of kinetic energy in bullets is tied (somewhat) to velocity.
The damage that occurs in an organic body due to the hole that was punched into it is permanent.

Now, having said this, there are hydrostatic consequences related to the event. Rounds that are traveling at or above Mach 2 (read 2,200 fps) will, as a consequence of their passage, distribute a shock wave that is violent enough to destroy tissue due to the shock wave alone. The "collateral" damage caused by the shock wave rolls off (almost logarithmically) as the velocity is reduced, so much so that projectiles at Mach 1 (read 1,100) experience almost no "benefit" from hydrostatic shock. The shock wave is still there, but the tensile strength of most organic substances (like muscles and organs) can stretch and recover from the shock wave without notable damage. (It takes Mach 2 to snap the rubber band). This is just a fact.

So, for most pistol cartridges, the concept of "energy dump" as a mechanism of destruction simply doesn't apply. The liver is less able to put up with compression and can be more readily damaged by lower velocity shock waves. Sadly, destroying the liver will not stop the vital functions needed for the bad guy to continue to operate (for at least a few hours).

Neurological or cardiovascular shut down is the only thing that a pistol round can do to "guarantee" an immediate cessation of the activities of any living entity so engaged.

Psychological factors kick in at some point. In simple terms some people can "take a hit" better than others. However, you can't depend on this. Pain, and the realization of "oh my God, I've been shot" may not be enough to stop your bad guy.

If you can effect damage to the heart, superior/inferior vena cava or aorta you stand a good chance of dealing with an adversary that will (no matter what) become incoherent in 10 to 15 seconds. Of course any neurological hit is probably an instant winner (if you can call it that).

It is what it is my friends.
Just remember, our deer rifles push bullets at Mach 2+ for a reason.

bob
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Old July 13, 2007, 05:29 AM   #15
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energy

double the weight of a bullet and it doubles the energy.
Double the speed(velocity) and it has 4X the energy.
Ideally a bullet will expand and penetrate without losing weight.
If you find a .270 caliber bullet has expanded to .5 without loss of weight and penetrated to the far side of the target without exiting 100% of the energy is transfered and near maximum penetration.
What I look for in a deer round is expansion and penetration.
I like the bullet to expand as much as possible and exit leaving a second larger hole to allow blood to excape.
Heart shots provide nice easy to follow blood trails.
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Old July 13, 2007, 06:52 AM   #16
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To me its simple, get a bullet that will penetrate far enough to reach the vitals, that is what counts.

A larger caliber bullet will destroy more tissue but have a more rainbow trajectory

A smaller bullet will have a flatter trajectory but not leave as big of a hole.
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