Questions about the irrelevance of energy (ft-lbs)

[Skydog]

I'm a recent convert (at least in theory) to the concept of using smaller calibers with light fragmenting bullets on big game. So, bear with me if these are dumb questions. I'm still having to work through and unlearn some previously held beliefs about "knockdown power".

I have read pages and pages of threads here at RS and I feel like I have a pretty good grasp on the concept, but...

I have read many comments stating things like "energy is a totally irrelevant/meaningless metric in terminal performance or effectiveness on game", the "myth of energy", etc.

However, I also see comments from advocates of the small caliber/fragmenting bullet school, that state things like "you don't want the bullet to exit because you want the full energy dump inside the animal and not on the dirt behind the animal" when discussing penetration. Statements like these seem to imply that there is some significance/benefit to having more energy transfer to the animal, otherwise why would one care if some of that energy is lost due to over-penetration/exit?

How do you square the idea of energy being totally irrelevant with also claiming the advantages of a full energy dump from the bullet? This seems inconsistent and contradictory. If energy is really irrelevant, why do I care if some of a bullet's energy is "wasted" on the dirt after exiting the animal? How is energy wasted if it is irrelevant to begin with? And why is more of an energy dump better than less of an energy dump if energy is truly irrelevant?

All other things being equal, is there or is there not an advantage of a 1500 ft-lb "dump of energy" versus a 1200 ft-lb "dump of energy"?

Hope my questions make sense...

 

[Formidilosus]

I'm a recent convert (at least in theory) to the concept of using smaller calibers with light fragmenting bullets on big game. So, bear with me if these are dumb questions. I'm still having to work through and unlearn some previously held beliefs about "knockdown power".

I have read pages and pages of threads here at RS and I feel like I have a pretty good grasp on the concept, but...

I have read many comments stating things like "energy is a totally irrelevant/meaningless metric in terminal performance or effectiveness on game", the "myth of energy", etc.

However, I also see comments from advocates of the small caliber/fragmenting bullet school, that state things like "you don't want the bullet to exit because you want the full energy dump inside the animal and not on the dirt behind the animal" when discussing penetration.

Who has stated that? I can all but guarantee you it isn’t from anyone that understands terminal ballistics.


An upsetting bullet exiting means that it could have caused more tissue damage inside the animal by either expanding wider, or fragmenting more. “Energy dump” is just as useless as ft-lbs of energy number to know what a bullet will do.

All other things being equal, is there or is there not an advantage of a 1500 ft-lb "dump of energy" versus a 1200 ft-lb "dump of energy"?

How do you know that it “dumped” 1,500 ft-lbs or 1,200ft-lbs of “energy” inside the animal? And, what did that supposed energy do?
In neither case can the “number” tell you a single thing about how deep a bullet penetrated, how wide the wound was, or the overall shape.

 

[Bugger]

However, I also see comments from advocates of the small caliber/fragmenting bullet school, that state things like "you don't want the bullet to exit because you want the full energy dump inside the animal and not on the dirt behind the animal" when discussing penetration.

Change the term “energy dump” to “wounding potential” and it makes more sense. Wounding potential is everything, and a fragmenting bullet is more likely to do the most wounding where it counts vs a bullet designed to hold together longer and make a more narrow channel that penetrates way past the vitals into more muscle, hide, and dirt on the back side. When you start at that mindset, added diameter and bullet weight mean less than the traditional trend towards a big stout bullet that pokes two holes.

 

[EastHumboldt]

I’ve garnered two important points from all these discussions.

1) Smaller, lighter kicking cartridges greatly improve your chances of hitting where you’re aiming, making you a deadlier shooter. Finding a load, factory or hand loaded, that groups well out of,your particular rifle is a paramount consideration.

2) The projectile you choose must maintain enough velocity to expand or fragment, within the ranges you intend to shoot, therefore doing the job of causing a bunch of damage in the boiler room.

IMO The rest is somewhat academic.

 

[Skydog]

Who has stated that? I can all but guarantee you it isn’t from anyone that understands terminal ballistics.

I have seen it stated almost word for word, or in a very similar manner, on different threads here at RS. The only way I can identify the "who" is to directly quote them and I didn't want to do that. I'd also have to go back through a bunch of threads to find them. But I assure you that I am not making them up. Perhaps these folks don't understand terminal ballistics. I don't know the answer to that.

An upsetting bullet exiting means that it could have caused more tissue damage inside the animal by either expanding wider, or fragmenting more. “Energy dump” is just as useless as ft-lbs of energy number to know what a bullet will do.

OK...so there is an advantage to the bullet not exiting (i.e. more tissue damage), but it has nothing to do with "energy dump"...correct? Thank you for the clarification.

How do you know that it “dumped” 1,500 ft-lbs or 1,200ft-lbs of “energy” inside the animal? And, what did that supposed energy do?

Using the same ballistic tables/data that are used to estimate velocity at impact, couldn't one get a somewhat close approximation of energy at impact? I don't know what the energy supposedly does other than the "energy dump", whatever that means...I assume it equates to something akin to "knockdown power".

In neither case can the “number” tell you a single thing about how deep a bullet penetrated, how wide the wound was, or the overall shape.

OK...understood.

 

[Maverick1]

I'm a recent convert (at least in theory) to the concept of using smaller calibers with light fragmenting bullets on big game. So, bear with me if these are dumb questions. I'm still having to work through and unlearn some previously held beliefs about "knockdown power".

I have read pages and pages of threads here at RS and I feel like I have a pretty good grasp on the concept, but...

I have read many comments stating things like "energy is a totally irrelevant/meaningless metric in terminal performance or effectiveness on game", the "myth of energy", etc.

However, I also see comments from advocates of the small caliber/fragmenting bullet school, that state things like "you don't want the bullet to exit because you want the full energy dump inside the animal and not on the dirt behind the animal" when discussing penetration. Statements like these seem to imply that there is some significance/benefit to having more energy transfer to the animal, otherwise why would one care if some of that energy is lost due to over-penetration/exit?

How do you square the idea of energy being totally irrelevant with also claiming the advantages of a full energy dump from the bullet? This seems inconsistent and contradictory. If energy is really irrelevant, why do I care if some of a bullet's energy is "wasted" on the dirt after exiting the animal? How is energy wasted if it is irrelevant to begin with? And why is more of an energy dump better than less of an energy dump if energy is truly irrelevant?

All other things being equal, is there or is there not an advantage of a 1500 ft-lb "dump of energy" versus a 1200 ft-lb "dump of energy"?

Hope my questions make sense...

Sufficient energy is needed to ensure proper projectile expansion. Beyond that energy is irrelevant. The resulting tissue damage from proper projectile placement is key.

Plenty of elk have been killed with a 6mm projectile having “only” 80 ft-lbs of KE. Right through the heart or lungs and they die. Every single time.

 

[Skydog]

Another follow-up question...

We use the same metric (ft-lbs) to measure recoil that we use to measure muzzle energy and impact energy at 100, 200, 300 yards, etc.

Recoil applies force - you might even say "knockdown power/energy dump" to our bodies (shoulder, neck, head, arm, etc.) when we shoot. It can be powerful enough, even at just 15 to 20 ft-lbs. of recoil, to knock someone down (depending on size) or damage a shoulder, etc.

Some people make a big deal about even a minimal reduction in recoil.

Why is it that something like a 3 ft-lb. difference in recoil is considered significant by some people, but a 300 - 400 ft-lb. difference in energy on a deer is irrelevant?

I realize it's not a 100% apples to apples comparison, but wouldn't there be some equivalency/similarity since they use the same measurement of energy (ft-lbs)? If 20 ft-lbs of energy can damage a human shoulder or knock a 100 lb. child to the ground, how is it that 1700 ft-lbs* of energy won't damage a deer's shoulder or knock a 100 lb. deer to the ground?

Full disclosure...I don't fully understand terminal ballistics, and I'm not trying to be argumentative or debate anyone...just trying to learn.

*Winchester Silvertip .243 Win 95 grain = 1719 ft-lbs of energy at 100 yards

 

[hereinaz]

Using energy as a factor is meaningless.

The only thing that matters is sufficient tissue destruction to stop brain function as the result of blood loss (or permanently disrupt the central nervous system but that's a different story).

Tissue destruction by the bullet is the measure.

The level of destruction can be separated into categories by bullet type, from least to most destruction:

• mono
• bonded/partition
• fragmenting

Another choice between bullets is penetration, but it isn't based on destruction as much as it is trying to get a blood trail with an exit to track them. Generally, the more penetration the less fragmenting, but I have seen exits at long range with 180 Bergers.

 

[Colorado Cowboy]

I like to eat my game meat not mangle it. I tried my ,220 Ackley Improved Swift one year in Wyoming on antelope. I shot an antelope at 200 yards and it dropped like a rock. I thought great kill. When I was skinning it I found bone and meat ground up like hamburger meat with bullet fragments everywhere.. I ruined the whole shoulder. I was shooting a 53 gr Sierra bullet and 43 gr RL 15 at 4,000 fps.

I'll stick to my 25-06 using my reloads with a 117 gr sierra and 3100 fps.

 

[fmyth]

Sufficient velocity is needed to ensure proper projectile expansion.

Fixed it for you.

 

[Tmac]

@Skydog I learned a long time ago to focus on accurately placing a bullet capable of killing my target within the velocity window it reliably expands in. Do that and stuff dies fast. A bullets size in comparison to a big game animal is tiny, 100gr or 200gr bullets, both tiny compared to the weight of the quarry. The ft lbs number can look like a big difference, but it’s still tiny. It’s usually very difficult to tell which bullet was larger when examining wounds, for bullets of similar construction impacting at similar speeds. This is despite often seemingly large differences in ft lbs.

Ft lbs uses mass and velocity to calculate a number. Not unlike calculating HP for a motor. It’s nice to have but mostly worthless in determining what happens upon impact. So I’ve learned to focus on bullet construction and impact velocity to give me a reasonably good idea what happens on impact. Above @hereinaz gives you some good factors to consider in picking the bullet for the terminal result you desire.

 

[Marbles]

Kinetic energy (KE) does not meaningful translate into energy transfer to tissue, in part because that transfer takes multiple forms. But, yes, all else being equal more KE means more potential tissue damage by energy transfer. The problem is all things are never equal.

The most efficient and complete energy transfer is less lethal rounds like rubber bullets, but the manner of that transfer actually makes killing less likely.

Similarly, arrows are very bad at transferring energy to a target, and have low KE to start with, but the natural of the transfer makes them pretty lethal.

KE fails to describe relative wounding potential, unless talking of the exact same projectile, in which case velocity is a more intuitive and useful concept. Further, KE is badly misunderstood by most, making it even worse as a descriptor because people don't actually know what they are talking about.

Even in trauma, penetrating wounds are categorized as high (generally above 2000 fps) or low (generally below 2000 fps) velocity. This reflects that velocity, no KE is what matters in the nature of a wound.

Similarly, bullet manufacturers discuss expansion velocity, not expansion KE. The fact that velocity is part of KE doesn't change the fact that the two are very different metrics and velocity is the more functional of the two.

Further, what is the killing difference of a 7 PRC at 50 yards vs 650 yards using a 180 gr ELDM? What is the energy differenc?

50 yards 3217 ft.lb
650 yards 1798 ft.lb
=1419 difference.

My 243 has more energy at the muzzle using a 108 ELDM (1948 ft.lb) than a 7 PRC at 650. What does that tell you about how well each kills? If KE is meaningful, than those who argue for "energy" must admit that a close range 6 creedmoor shot is more effective than a long range 7 PRC shot. Good luck getting that kind of consistency in those arguments.

 

[Skydog]

I remember reading in another thread that a mere 10 ft-lbs. of recoil from a .243 Win. causes enough force on the head/neck of an 80 lb. child to approach TBI levels. I've also been told by my doctors/surgeon that I need to minimize recoil to avoid further injury to my neck/shoulder.

So...I'm still trying to wrap my head around how 10 ft-lbs of energy can cause TBI in an 80 lb. child, create issues for my cervical fusion, cause further damage to my shoulder joint/rotator cuff, etc...but 1700 ft-lbs of energy on an 80 lb. deer is irrelevant.

 

[Skydog]

Just to be clear...I'm not arguing for more energy or defending the concept of "knockdown power". I am fully convinced of the ability of small fragmenting bullets to kill large game. The evidence put forth on this site cannot be disputed. I plan to go forth this fall with a .243 Win 95 grain NBT or 90 grain ELD-X, and I fully expect it to do the job. I'm just trying to work through a few lingering questions, things that don't quite make sense yet, etc...

Again, not looking to debate...just seeking clarity.

Thanks all for the responses!

 

[blkqi]

I remember reading in another thread that a mere 10 ft-lbs. of recoil from a .243 Win. causes enough force on the head/neck of an 80 lb. child to approach TBI levels. I've also been told by my doctors/surgeon that I need to minimize recoil to avoid further injury to my neck/shoulder.

So...I'm still trying to wrap my head around how 10 ft-lbs of energy can cause TBI in an 80 lb. child, create issues for my cervical fusion, cause further damage to my shoulder joint/rotator cuff, etc...but 1700 ft-lbs of energy on an 80 lb. deer is irrelevant.

Energy is very relevant to a blunt force impact.

Penetrating trauma is a different beast.

 

[Shortschaf]

Why is it that something like a 3 ft-lb. difference in recoil is considered significant by some people, but a 300 - 400 ft-lb. difference in energy on a deer is irrelevant?

So...I'm still trying to wrap my head around how 10 ft-lbs of energy can cause TBI in an 80 lb. child, create issues for my cervical fusion, cause further damage to my shoulder joint/rotator cuff, etc...but 1700 ft-lbs of energy on an 80 lb. deer is irrelevant

Because RECOIL is a SIMPLE, CONSISTENT transfer of energy from an explosion, to stock, to shoulder. It's the same impulse every time a rifle fires with the same ammo and shooter, and only varies between different rifles because of weight, muzzle devices, and the recoil pad--all of which produce predictable affects

Energy transfer of a bullet to an animal's anatomy is NOT simple or consistent enough to draw conclusions. Results of "damage" are not quantifiable and too many factors have dramatic affects on results: bullet type, impact angle, impact location, and biological differences from animal to animal

 

[nobody]

If energy mattered, bullet/ammunition manufacturers would provide a “minimum impact energy” threshold for their bullets instead of a “minimum impact velocity” threshold.

All bullets in a given line, be it an ELDX or a TTSX or any other bullet, lists a minimum impact velocity threshold for adequate expansion and terminal performance. Whether that projectile is fired from a 243 or a 30-378 weatherby is irrelevant, the minimum impact velocity is the same for a given bullet line, even though the 2 cartridges I just listed give VERY different energy values at their minimum impact velocity threshold because of grossly different bullet weights.

Just because you can solve for it (energy), doesn’t mean it tells you anything about wound channels. You can shoot an animal with an FMJ from a 300 win mag, and shoot the same animal from the same distance with an ELDX and have VASTLY different wound channels, even though their energy values are the same. Heck, you could shoot an animal at distance with a TTSX and an ELDX and have vastly different terminal effects between the 2, even at the same velocity AND energy.

It’s all about projectile design and velocity. That’s all that matters. 1800 FPS impact from a hornady 140 ELDM fired from a 6.5 CM will have superior terminal performance to that of a 300 WM shooting 180 grain TTSX’s, even though the 300 has a higher impact energy and the same velocity, it’s all moot because of the differences in projectile design.

Fragmenting bullets, impacting in front of the diaphragm fast enough to expand and do damage, kill every time, no matter the energy.

 

[prm]

I'm a simple man. If an arrow through the vitals kills an elk, any rifle bullet that expands meaningfully is going to meet or exceed the arrow/broadhead damage. Thus, it's "enough". No math is required to to draw that conclusion.
Internally, I remain irrationally more 'confident' in fat .338 bullets vs. skinny 6.5 bullets when hitting elk, but my actual experience is that they both work just fine. So I just go with it and know from experience that my choice between my .338 or my 6.5 is irrelevant towards the outcome. That, and that my grandfather and uncle killed elk just fine with 257s. For the OP, skip trying to figure out the and go confidently with your 243, it will work fine.

 

[Tmac]

I remember reading in another thread that a mere 10 ft-lbs. of recoil from a .243 Win. causes enough force on the head/neck of an 80 lb. child to approach TBI levels. I've also been told by my doctors/surgeon that I need to minimize recoil to avoid further injury to my neck/shoulder.

So...I'm still trying to wrap my head around how 10 ft-lbs of energy can cause TBI in an 80 lb. child, create issues for my cervical fusion, cause further damage to my shoulder joint/rotator cuff, etc...but 1700 ft-lbs of energy on an 80 lb. deer is irrelevant.

I'd guess you are looking at a recoil calculation for a given rifle weight. The rifle weight matters a lot. In a sense the mass of the rifle absorbs some of the recoil. If that rifle weighed a ton, there would no recoil felt at your shoulder.

Pick a moderate cartridge, suppress it, and your recoil issue is greatly mitigated. Bonus is your ears and those around you will thank you.

 

[hereinaz]

I remember reading in another thread that a mere 10 ft-lbs. of recoil from a .243 Win. causes enough force on the head/neck of an 80 lb. child to approach TBI levels. I've also been told by my doctors/surgeon that I need to minimize recoil to avoid further injury to my neck/shoulder.

So...I'm still trying to wrap my head around how 10 ft-lbs of energy can cause TBI in an 80 lb. child, create issues for my cervical fusion, cause further damage to my shoulder joint/rotator cuff, etc...but 1700 ft-lbs of energy on an 80 lb. deer is irrelevant.

Why are you comparing that?

Again, it matters how the energy is applied.

Here’s a question you should answer. Which would you rather get shot with?

A solid caliber that doesn’t expand or a highly fragmenting bullet? For these purposes, you can assume the velocity is 2000 feet a second and the copper bullet weighs twice as much as the highly fragmenting bullet.