View Full Version : Terminal Energy

Northwest Cajun
June 26, 2001, 02:03 PM
Hi Guys,
Would it make a difference in bullet weight if the ammount of foot pounds are the same at a given distance?
Let me explain, I'll be going Elk hunting this fall and I have narrowed my choice of bullets between a 180gr or a 165gr Partition in a .30-06 both loaded to give 2000 Ft/lbs at 200 yds. Would the Elk know the difference?

June 26, 2001, 05:47 PM
All else being equal? No. But all things aren't equal. What you want to do is ensute that kenetic energy is delivered INTO rather than through/behind or on the surface of the tatget. That's why highly fragmentary bullets are not really lethal on thick skinned critters and solids are virtually useless on thin-skinned critters.

Think (infinetesimally light) Bean-bag or Ice-Pick

What is the overall expansion & weight loss of each type of bullet in test media? Choose the one that expands best in approximation to hide & muscle of your tatget elk yet has enough weight retention and penetration to break a shoulder or rib.

Just remember, If you can't find the bullet when you clean it, your bullet was wrong but your shot placement good.

All I say is by way of discourse, and nothing by the way of advice.
I should not speak so boldly if it were my due to be believed.

* Honor Before All - Doing Least Harm Always

June 26, 2001, 06:06 PM
"Just remember, If you can't find the bullet when you clean it, your bullet was wrong but your shot placement good. "

Interesting statement, I've always heard/read/been told that you wanted a bullet that would expand and penetrate all the way through since (in theory) bleeding from 2 holes is better than 1 and exit wounds bleed more than entry wounds. Is this idea false, or does it only hold true for handguns and not rifles?

I confess I'm not a hunter so I'm going on what I've heard from many other sources and not from personal experience.

Bud Helms
June 26, 2001, 10:54 PM
For years there's been discussion among hunters of whether punching through an animal or expending all the energy available into the animal is best. I really don't know, but I'll say this ... if the shot is placed correctly, the difference is academic. If the proper bullet for the game is used it matters even less. "Punching through" to leave a blood trail is planning for failed shot placement in some hunters' opinion. The only time I ever hope a shot goes all the way through is when I'm muzzle loader hunting. It hardly ever does, though. I personally subscribe to the theory that all available energy expended into the game increases the liklihood of a clean kill. That assumes correct (favorable) shot placement.

June 27, 2001, 01:11 AM
180 Grains.

Holds on to energy better, trajectory differance NOT important on an Elk sized target.

Deeper penetration better on a quartering shots.

No one ever says "Damn that bullet was to heavy" on a Elk Hunt.

June 27, 2001, 11:37 AM
Of course, with the critters I'm shooting at, at the ranges I hunt (pistol) I like to see 150% energy transfer. If it isn't stopped in its tracks and even knocked physically back a couple of feet it might still get me. Any bullet that goes through has "wasted" a goodly portion of its energy.

Polar Bear, 50 feet. :eek:
Whadda ya want? Through-shot or sledgehammer? :D

.454 350gr LBT @ 2200ft-lbs. 6" tube

"It's an .88 Magnum, it shoots through schools." Johny Dangerously

Northwest Cajun
June 27, 2001, 12:34 PM
I'm not going to get in the middle of the exit holes debate.
I was just asking if there was a difference in between a 165gr traveling 2800fps and a 180 going 2600 in a 30.06 . Using a ballistic calculator(JBL) they both have approximatly the same energy at 200 yds.
180gr Partition:

165gr Partition:
I can get 180's to print 1" @ 200yds from a bench. but with a load that is only pushing them at 2490 fps( deer load)
I'll try to see if I can get the 165's to shoot that good at 2800fps(hopefully)
I'm using an custom sporterized '03 Springfield MK1 with a barrel dated 11/ 17

Keith Rogan
June 27, 2001, 12:50 PM
Let's examine this in a clear light. I'll exclude muzzle loaders and handguns here because the parameters are so different, and stick strictly with rifles appropriate for the game being hunted.

Let's say the animal being hunted is 18" thick - a big, beefy mule deer for example.
There are two animals of the same size standing side by side and both you and your partner shoot one at the same time, in the same spot on the body with identical .30 caliber rifles but using very different loads.
One bullet penetrates 12" and stops, while the other goes all the way through. Both bullets have expanded a similar amount so the penetration is due strictly to the kinetic energy (weight and velocity) rather than due to something like a full metal jacket round "zipping" though the animal.

Two points here - it takes the same amount of energy to penetrate that first 12" of meat and bone for either round, so the second round (the round that exited) transferred 1/3 MORE energy than the first round which "expended all of it's energy within the animal" - since it went through an additional 6" of resistance.

The second point has to be drawn from the conclusions of the first point. Since both rifles are the same caliber, you in effect must DOWNLOAD a round with either less weight or less velocity (or both), to NOT go all the way through since any centerfire rifle round appropriate for a particular game animal is capable of both good expansion and complete penetration.

In the real world this probably doesn't matter very often since both rounds penetrated the vital organs of the animal. But the argument of "complete energy transfer' is a hollow one since such loads have to carry less energy in order to fail to penetrate as far.

In my view, the round that exits transfers both MORE energy AND gives you an edge - that exit wound blood trail if you screw up. And if you shoot enough animals you WILL screw up eventually. Even well-shot animals will often go a surprising distance and lay down in the brush. You can either say "No blood trail, I must have missed" or "Look at this trail of bright orange lung blood, let's follow it", depending on the load you use.

June 27, 2001, 01:03 PM
The 180 grain bullet has a higher sectional density than the 165. In plain english, given the same rifle/caliber, the 180 grain is going to penetrate further into the animal than the 165 by a small margin, which MIGHT be an advantage as an all aspect bullet. Test your rifle/bullet combination to see. I know those elk hunts aren't getting any cheaper, and best of luck to you!

Keith Rogan
June 27, 2001, 01:11 PM

Either round will work. I think the 180 grainer will penetrate further and give you a slight edge, but i don't think you'd be going wrong with either of these - Nosler Partitions are good bullets.
It matters not a whit if your bullet hits an inch or so to one side of the other of where you place your crosshairs. What counts is what that bullet does when it hits, so if it was me I'd go with the extra weight (on an elk at any rate), and not worry about any slight accuracy edge.

June 27, 2001, 02:32 PM
I use 180 Sierra GameKings in my '06 & 165 Barnes XBT in the .308 - ~2700 & 2400 fps in 22" & 18.5" tubes respectively. Both have a very good kill results on elk.

I use the lighter weight .308 mostly these days & use the Barnes to "make up" in penetration due to the lower speed afforded by the shorter barrel.

Zorro was right re "no such thing as too heavy a bullet for elk." But, penetration's the key, right after proper placement. Either 165 or 180 in the Partition will do the trick for you.

Art Eatman
June 27, 2001, 07:06 PM
Considering that deer-family critters can run 50 to 100 yards (and per some folks, more) with the heart blown all to pieces, an exit wound which leaves a good blood trail is no bad thing.


June 28, 2001, 11:55 AM
Keith - RE: Two points here - it takes the same amount of energy to penetrate that first 12" of meat and bone for either round, so the second round (the round that exited) transferred 1/3 MORE energy than the first round which "expended all of it's energy within the animal" - since it went through an additional 6" of resistance.
I would grant you the point, but the question as given assumes at the total energy is supposed to be equal at 200 yards. Thus, any through-shot will have by definition NOT have imparted the full 2000ft-lbs to the target.

Think about it for a minute. if you only have 2000 ftlbs to work with vs. a Kodiak Brown, do you want to keep all 2000 or would you be willing to settle for 1500?

(Were we talking about this in any other frame of reference I would agree with what you said.) ;)

Bud Helms
June 28, 2001, 07:12 PM
MrMisanthrope: "... the second round (the round that exited) transferred 1/3 MORE energy than the first round which "expended all of it's energy within the animal" - since it went through an additional 6" of resistance."

I'm thinking there's some food for thought here ...

June 28, 2001, 07:44 PM
Sensop, that was Keith's point and I was rebutting it for the puropses of this incidend and these circumstances.

It's a good point but not applicable here. Credit where credit is due.

Bud Helms
June 28, 2001, 10:32 PM
Aha. I see that I CAN read, but only if I slow down to actually do it.

Keith Rogan
June 29, 2001, 05:19 PM
Yes, I can see that in this particular instance the paper energy of both rounds is the same at 200 yards, and perhaps the equation falters - if you can guarantee your elk will be at precisely 200 yards.
However, what is the energy at 150 or at 250 yards? There is no such thing as a free lunch even in the arcane world of ballistics. At some point the bullet weight you trade off for velocity equates to a loss of energy - of penetration.
And when all is said and done, it's rarely the "energy" that kills (though I do believe hydrostatic shock is real), it's disruption of organs and bleeding that is the "sure thing". The more of the animal penetrated, the more sure the kill.

With that said, I'm not a heavy bullet fanatic. I just think you should use enough bullet for the animal being hunted. An elk is a big animal though, and I would lean towards the heavier bullet.

June 29, 2001, 05:26 PM
the bullet that does NOT go all the way through will be more effective in my eyes because it will unleash all of its energy inside the animal, but the one that goes all the way through won't because it'll still be traveling after exiting the other side which will mean that it still has energy and therefore didn't unleash ALL energy inside the animal. the other one did, so therefore will be more effective. the more energy absorbed by the animal will mean the more shock produced and that is how bullets usually kill animals...by shock which stuns the vital systems and kills the animal. arrows kill by causing the animal to bleed to death, not by shock, which in my opinion is more effective.