# what does energy gain you?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by TheFishBox, Dec 22, 2013.

1. ### TheFishBoxWell-Known Member

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As the title says what does energy gain you when it comes to long range hunting. I just watched that long range pursuit video for the hundredth time when the kid kills a bull at 1300 yards with a 7mm rem mag shooting a 168 or something grain bullet and trying to figure out why I think I need more energy than that to kill one.

So does more energy really help you or just make you feel more confident to take a shot in worse conditions? Cause we should always think we are going to hit the kill zone if we squeeze the trigger so why do I need more energy? Trying to justify keeping my 338am.

2. ### Michael EicheleWell-Known Member

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This is a complicated subject. Energy has a place but I think it gets too much attention.

Honestly, I feel that energy in this context is nothing more than a mathematical equation based on velocity and weight. What is important here is energy transfer. Mathematically, a full metal jacket has the same impact energy as a mushrooming bullet at the same weight and speed. Which one do you think will affect the animal more?

Arrows offer well under 100 pounds of impact energy but are devastating on even the largest game. It's tissue destruction here that matters. That said, a field point will kill by hitting lungs but very slowly as soft tissue tends to seal shut unless you tear a gaping hole such as what a broad head or expanding bullet does.

Energy transfer if large enough can shock an animal to the point that their legs will just give and they fall down. So yes, energy can be important but the most important factor IMHO is creating a permanent wound channel to allow for severe and quick blood loss and/or air loss. Assuming you're taking heart/lung shots which a lot of us do.

Sectional density along with 'energy' allows for deep penetration but sectional density IMHO is the larger factor of the two.

Big boomers that generate massive amounts if energy are fun and all but they have a price. They shine best when shots are really long such as over a grand or well over a grand for that matter. Then it becomes a matter of sufficient energy at really long range.

In short, I believe that the two most important factors aside from putting the bullet where you want/need it is sectional density for deep penetration and expansion for tissue destruction and the transfer of whatever energy you do deliver.

3. ### midwesthunterWell-Known Member

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The way I see it you have needed energy to humanly kill an animal, me I'm in favor of having more than needed energy. Not all shots are perfect broadside shots. Maybe you need to put one in a quartering away animal. Me I want a bullet that will drive all the way trough even quartering away. Or I want enough energy if bullet has to bust through the shoulder. You can kill an animal with a lesser cartridge, but bullet placement better be perfect. Me I say we owe it to the animal to put it down as quick and humanly as possible.

4. ### sp6x6Well-Known Member

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For the example you just gave I would take the 338 am everytime. I know Ill catch it but Im a dedicated elk hunter and I walked away from my 7 RM 25 years ago because I felt like I was pushing it to its limits.1300 yrds is a long ways for a 7mm. And for 98% of your shots I dont think you need the 338 AM you have,that 338 Kirby built Lapua is just fine

5. ### MontanaRiflemanWell-Known Member

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If you notice in that video, that bull walked or trotted away and it didn't look like it was hurting too much. Fortunately for the hunters it fell or laid down before it wandered too far. You'll notice there was a large party to pack it all out. Had that bull wandered back into steep dark timber and blow down it would have been hell for them... if they found it. I don't recall whether there was an exit or not.

They made their choice and it's their choice to make, but I would never have taken that shot with that bullet and rifle at that range. That bullet was on the very ragged edge of performance which makes it too risky for me.

Now you ask about energy. Do you know what energy is and how it translates to killing? What you are talking about is KE or kinetic energy. A good defintion fo KE can be found on Wiki

In physics, the kinetic energy of an object is the energy which it possesses due to its motion.[1] It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body in decelerating from its current speed to a state of rest.

The last sentence should read... The same amount of work is done to decelerate the body from its current velocity.

The formula is Ek = 1/2 (mass x velocity squared) Just how does that translate to killing on the receiving end? IMO, it's very abstract.

There are a couple other terms and formulas to consider.

Force... Force = Mass x Acceleration or F = ma It takes a certain amount of force to accelerate a bullet (M) up to a certain velocity. When the bullet leaves the muzzle the counter force of friction of air begins to decelerate it and when it strikes its target the target provides another source of friction to further decelerate it.

Momentum... Momentum (p) is a straight up relationship of Mass and Velocity. p = mv When a bullet strikes a target or animal it has a certain amount of momentum based on its mass and velocity. Bigger bullets with same velocity have more momentum. Faster bullets of same size have more momentum. The animal's flesh and bone resist (friction) the bullet and cause it to slow down, decreasing it's momentum. The result of that resistance of the flesh and bone is the destruction of the same. Momentum gives us an idea of the potential the bullet has to penetrate and cause damage. However, there are many variables in that potential based on the design and construction of the bullet. So it becomes and educated guessing game which we mostly learn through experience... ours and others.

If you have say, a 168 gr bullet with an MV of 3000 fps it's KE is 3358. That's a big number and very impressive and attention getting. It's momentum is only 72. That's not very impressive... but it's the same D#%m bullet!

Back when the magnum craze started, the marketers used KE numbers to market their high speed magnums... because the KE formula gives more value to velocity than mass. But it is not really a true representation of a load's potential. For some reason it hangs on and people focus on it making judgements with it not knowing what it is ans isn't.

Take for instance a 53 gr Vmax @ 4000 fps out of a 22-250 and a 240 gr hard cast @ 1000 fps out of a 44 mag. The Vmax has 1883 KE and the hard cast has 533. Which one would you want to defend yourself against a big bad 500 lb bear 20 yds away? The Vmax of course!!! Right? Wrong! The Vmax would only reeeeealy piss him off! BTW the momentum of the 53 gr Vmax is 30 and the momentum of the 240 gr Hard Cast is 34, still not quite an accurate representation of the potential of the bullets, but better than KE.

Bottom line, I do not look at KE for killing potential. I look at the caliber, size, design and construction of the bullet and its velocity and consider its anticipated minimum performance velocity.

I would be inclined to pad that minimum performance velocity for smaller bullets.