"Knockdown Power"

I think part of the problem stems from the assumption that any person using the term "Knockdown power" saw a movie where some powerful gun picked a bad guy up and tossed him like a rag doll, and believed the real world works that way.

Not understanding that the guy using that term is nowhere near that stupid, we then jump on him with both feet and berate him (Smug in our superiority) for believing in something that's as dumb as a Scooby-Doo cartoon.

I can't imagine any person that's fired one whole box of real rifle ammo thinking they could actually lift any animal off it's feet and throw it by hitting it with a bullet. I've never met anybody that stupid, and doubt I ever will.

I'm pretty sure that Good Ol' Boy above is correct. Some bullets have more power than others, and the goal is to put the animal on the ground. Calling it "Knockdown Power" isn't incorrect if you forget about all that science stuff and just accept it as a slang term.

Slang terms, for those that don't know, don't require accuracy. For example, the term that says "You can kiss my" doesn't actually grant permission for anybody to kiss anything. It's merely a slang term that expresses contempt.

Getting all scientific and trying to calculate the mathematical variations of such a smooch doesn't make me smarter, it shows that I don't understand.

Get it?

Fast Frank said:

I can't imagine any person that's fired one whole box of real rifle ammo thinking they could actually lift any animal off it's feet and throw it by hitting it with a bullet. I've never met anybody that stupid, and doubt I ever will.

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I’ve had that exact argument many times over the years. Many gun owners believe a bullet can literally knock people down.

One argument was when someone here on THR (or maybe it was TFL) claimed that when he shot a deer and it jumped eight feet to the side, that was due to the kinetic energy of the bullet. He was claiming that a rifle bullet has the power to move a deer eight feet.

On one hand I agree most bullets cannot send most target critters "flying". That said if you where stand there unaware and relaxed and someone unnoticed by you walked up behind you and put a 300WM rifle next to the outside of your shoulder and pulled the trigger letting you absorb all that impulse completely unaware and unready I would bet that would knock most people down or at least send them staggering off to the side to catch their balance. There is a big difference between absorbing 4+ lb-s of impulse when you are anticipating it and in a good position as opposed to receiving that impulse out of the blue.

It's that OMG moment!
I have and can drop the largest and most dangerous of game animals at distances that would boggle the imagination.
But "Knockdown Power" isn't about how far away any Dangerous Game Animal is from you, place the muzzle of your firearm on an elephants temple and have it come to rest on or before the tip of your boot. Want a definition of "Knockdown Power" it's and end game changing dynamic that the BIGGEST and BADDEST of creatures have/or shall learn in the lessons of dynamics.
It's measured in inches not feet or yards. Don't make me pull up heart stopping videos to explain the subtle differences. Thanks.


It's going to get more exciting from here!

Perhaps this post won't go missing?

M118LR said:

It's that OMG moment!
I have and can drop the largest and most dangerous of game animals at distances that would boggle the imagination.
But "Knockdown Power" isn't about how far away any Dangerous Game Animal is from you, place the muzzle of your firearm on an elephants temple and have it come to rest on or before the tip of your boot. Want a definition of "Knockdown Power" it's and end game changing dynamic that the BIGGEST and BADDEST of creatures have/or shall learn in the lessons of dynamics.
It's measured in inches not feet or yards. Don't make me pull up heart stopping videos to explain the subtle differences. Thanks.


It's going to get more exciting from here!

Perhaps this post won't go missing?

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Lucky that idiot wasn't' killed. When shooting at a running smaller target if you stand and fire EVERY SHOT is at a different angle. Drop to one knee are fire STRAIGHT AHEAD as you would do at a range.

Theohazard said:

I’ve had that exact argument many times over the years. Many gun owners believe a bullet can literally knock people down.

One argument was when someone here on THR (or maybe it was TFL) claimed that when he shot a deer and it jumped eight feet to the side, that was due to the kinetic energy of the bullet. He was claiming that a rifle bullet has the power to move a deer eight feet.

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IMO, this is a perfect example of hitting a live animal, and when you hit nerves, etc, it's more of a galvanic response of nerve tissue reacting
to the pressure, pain, and velocity/impact of a bullet hitting tissue, rather than the body, as a whole, being forced in a direction by brute ballistic
force.

Cayce Charles said:

Lucky that idiot wasn't' killed. When shooting at a running smaller target if you stand and fire EVERY SHOT is at a different angle. Drop to one knee are fire STRAIGHT AHEAD as you would do at a range.

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Tawny Kitty number 1 was an excellent example of "Knockdown Power". Tawny Kitty number 2 ran in and whacked the rifle out of the "Great White Hunters" hand and ran away afterwards.

Knockdown Power and the Kinetic Energy required to Humanely harvest a game animal are not exactly the same conversation.

The kinetic energy to humanely harvest a game animal at distance while shot from ambush has been misinterpreted as "Knock Down Power" while being the HUNTED that requires a semblance of "Knockdown Power" has been dismissed or diluted into a convenient definition.

Bottom Line: Shooting a Southern White Tail at up to 300 Yards and Knocking Down MR. GRIZ, WHITE TEDDIES, or any of the BIG 5 at distances measured in inches AIN"T THE SAME THING.

JMHO.

Remember the old story about the Moro's shrugging off the ineffective 38's the Marines were using against them....so they brought back the 45 Colt's for more 'knockdown power'. What is conveniently left out of this often told story is that they also had 30-40 Krag's and they TOO were having trouble stopping the fanatical (and often drugged up) Moro's. Methinks the 30-40 has a wee bit more 'power' than even the mighty 45 Colt (and ACP) and if it was problematic when trying to stop one of the Indians from lopping off your head....the pistol also would have struggled. Shot placement is the best and only solution for stopping a charge once adequate penetration is achieved.

I was rooting for the lion.

M

CraigC said:

No such thing as "knockdown power" but we know what they mean. That said, there is no measuring stick. Kinetic energy is just a marketing tool for selling velocity. There is no mathematical formula that will tell us what we want to know. There are too many variables and too many ways to measure success and failure.

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I go back to the days before firearms were invented and look at how soldiers kill enemies. Simple, either a sword through the vitals, or an arrow through the same.

Although it was not documented but I highly doubt there were speculation that “kinetic energy” is key in killing your enemies, nor is the hydro-static shocks that destroyed his organs. The sword & arrow manufacturers at the time missed great opportunities by not having a marketing department!

One thing is clear, it was penetration & slicing & cutting major arteries/ organs along the way that provided the “stopping power”.

If I can make a bold extrapolation based on one data point, I’d say penetration and shot placement have the “first-order effect” on knockdown power.

Technically, there's no such thing as knockdown power for a handgun or a rifle. Do people fall down suddenly when hit with a .308? Yes they do but not from the bullet pushing them down. But when it comes to reality, a solid hit with a .308 is going to be very hard to survive and almost certainly the target is not going to be much of a threat any longer. So don't sweat it. Just consider the source and go about your business comfortable in the fact that you carry around some good knowledge about the subject.

I’ve seen some math on the .50 cal for knockdown power.

Taking the .50 bmg we have a mass of m1 = 0.05 kg and a velocity of u1 = 900 m/s.
The person has a mass of m2 = 80 kg and a velocity of u2 = 0 m/s.

The final velocity is then: v = (m1*u1 + m2*u2) / (m1 + m2) = (0.05*900 + 80*0) / (80 + 0.05) = 0.56 m/s

Which would move a person hit in the chest in theory 1.25 mph, but since life’s not perfect and it has enough momentum, it will go through you and not dump that full amount of energy AND STILL liquify your organs...so it will move you less than 1.25 mphs...hardly enough to send anyone flying down at the ground....but that’s a .50 we are talking about...so imagine now we take the math to say...a 9mm.
No ones getting knocked down simply by the bullet itself...or go flying back.

I just finished reading two excellent books. Elmer Keith's Rifles for Large Game and Terry Wieland's Dangerous Game Rifles. Keith's book has a date of 1946, Wieland's show 2009. Both men have hunted and killed a bunch of critters. Many of them were large, and many of them would kill the hunter - tap dance on one for a bit, anyway - should plans go awry.

Reading what they recommended and related, neither of them believe 'kinetic energy' ALONE is the criteria. They both mentioned success in shooting small game with high KE, but not in animals of deer size or larger. Absolutely not with critters with teeth and claws. They didn't use the term, but sectional density is a major factor. Without getting too technical, they prefer the heaviest bullet they could shoot with an impact velocity around 2100 to 2200 fps. In addition, the bullet had to stay in one piece when encountering the aforementioned critter and impact in a suitable place on the animal.

In short, no amount of energy (available in a human fired rifle) will terminate a dangerous beast if wounded in the foot or tail. They probably will be in an uglier mood than before. Plus, they have to be hit hard with a bullet that will suitably penetrate the beastie.

"Knockdown Power" in a hunting rifle is either a term for suitability and not literally correct, or a marketing phrase.

By the way, hydrostatic shock is difficult to achieve in a seven ton elephant.

M118LR said:

Tawny Kitty number 1 was an excellent example of "Knockdown Power". Tawny Kitty number 2 ran in and whacked the rifle out of the "Great White Hunters" hand and ran away afterwards.

Knockdown Power and the Kinetic Energy required to Humanely harvest a game animal are not exactly the same conversation.

The kinetic energy to humanely harvest a game animal at distance while shot from ambush has been misinterpreted as "Knock Down Power" while being the HUNTED that requires a semblance of "Knockdown Power" has been dismissed or diluted into a convenient definition.

Bottom Line: Shooting a Southern White Tail at up to 300 Yards and Knocking Down MR. GRIZ, WHITE TEDDIES, or any of the BIG 5 at distances measured in inches AIN"T THE SAME THING.

JMHO.

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Lion No. 1 shows the effect of a CNS shot: switch the lights out mid-flight. Whether the bullet had been a 6.5 or a .577, the switch-off would have been the same. Good shooting.

Lion No. 2... So many things wrong with these bozos, starting with the high fence in the background, that they only belong in the Hall of Shame.

So if a average size guy had an AR500 1” plate straped over his chest and got shot with a 50 cal what would the velocity have to be to knock him down or would it ever?

A friend of mine has a human torso silhouette that’s 2” thick mild steel. It’s on a chain, super heavy maybe 100lb. At 800 yards a 308 or 6.5 won’t even move it. You have to listen for the hit. It barely moves if you shoot it at 300.

WestKentucky said:

Slamfire ate his wheaties!

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And washed it down with a pot of coffee.
Its all good though!

I have read a LOT about how to gauge "knockdown" power and the consensus is that it is so variable that it is difficult to come up with a single number. As one poster said, a well placed .22 bullet is more effective than a .50 BMG that misses. For years, writers (and DNRs in many states) told us not to hunt deer with any firearm with less than 1000 ft-lbs of muzzle energy. Then you read about the Jordan buck which was estimated to weigh 414 pounds - taken with a single shot from a rather tame .25-20 which is probably more suited for coyotes.

William McKinley was assassinated with a .32 S&W, slightly less powerful than a .22 rimfire. President-elect Roosevelt was nearly assassinated with the same cartridge, but Mayor Anton Cermak of Chicago was hit instead and died (some opine that Cermak was so corrupt that it was a public service). The bottom line is that any cartridge can kill, it is a question of bullet placement. If the round is so powerful that you don't like shooting it, it may not be the best for you to use, non-withstanding that if it hits, it has more energy.

Wow quite a bit of misinformation, Roy Weatherby and gun writers did not invent modern ballistics. Neither did Taylor. Scientific engineers did. And the science of it has been determined for over a century although advances continue. Every major gun and ammunition company and major militaries have real certified scientists that spend thier career doing studies and know what they are doing. . Also Fackler is a coroner with no training in ballistics and much of what is he says is bias some lies and none of it actual scientific study. Really, study up on real experts with proven credentials.
The only accurate way the measure the potential of a projectile is kinetic energy . However the effectiveness of a particular cartridge is a combination of many factors. Ammunition should be selected by what it is designed for. But nothing is a substitute for proper bullet placement.

Momentum is a measurement of forces in involving solid objects. It has no bearing on soft tissue. It does have a bearing on bullet travel.Soft tissue is a combination of solid, liquid and flexible membranes. The forces that act on tissue are complex and not limited to direct tissue damage but also cavitation and energy transfer. The affects change with velocity as the way tissue behaves at higher velocity impacts and penetration is different than low velocity.

Kinetic energy is a measure of expendable workforce. Knockdown Power is a measure of over penetration and excess projectile diameter that equates to sufficient overkill to save your bacon at minimum distance in direct correlation to the size and ferocity of the "Charging Dangerous Game Animal" that you have now become Hunted by vice the Hunter of. Folks have shot and dropped Elephants with rifle/cartridge combos that Y'all wouldn't take into the woods to hunt Bambi. But that perfect shot might not be attainable when Dumbo has determined that your going to be part of the sticky mass between his toes. Kinetic energy once again is a measure of humanely harvesting a game animal at a specific distance while you are the ambush hunter. Knockdown Power is a measure of required OVERKILL to defend yourself while being hunted at distances measured in inches to keep you off the dinner plate. There isn't any definition of to much Knockdown Power, yet there is a definition of more recoil than the shooter can place on target. Location is everything, but when circumstances don't allow for pinpoint shooting, better have enough OVERKILL to hunt another day. JMHO.

JohnKSa said:

Mythbusters shot a dummy with an armor plate in its chest with a .50BMG at pointblank range. The bullet actually went through the armor plate but DID stop in the dummy's steel "spine".

So the dummy soaked up a pointblank hit from a .50BMG. It was dislodged from its supports (similar to what happened when it was hit with a thrown baseball) but it was not knocked backwards any appreciable amount.

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The math ain't hard, conservation of momentum requires that the momentum (mass X velocity of all objects involved in the collision) right before the collision has to be the same right after the collision.

Just before the collision assuming M2 ball ammo having a 709.5 gr. projectile at 2,810 fps there would be 8.85 slug-ft/s (lb-s) of momentum. If we assume the dummy weighs 200 lbs and the bullet stops on/in the dummy then the dummy and bullet (now stuck together) has to have the same 8.85 slug-ft/s of momentum just after the collision. This momentum would have the dummy & bullet moving at 1.42 fps (~1 mph) after the collision. Slightly slower than the person that fired the bullet since the target does not have to deal with the recoil from the propellant gasses.

Do the same math with a 100 mph (146.7 fps) fast ball (5.25oz) and you get the dummy moving at ~.25 fps

The conservation of momentum idea (Newton's first law) has been used to measure bullet velocity long before electricity existed to operate chronographs. Look up a "ballistic pendulum". It can be use at either end to measure both recoil of the rifle (rifle mounted on a pendulum) or bullet velocity at the pendulum catching the bullet.

Does replacing "Knockdown Power" with " Instantaneous Charge Stopping Ability " remove the kinetic energy confusion?

M118LR said:

Does replacing "Knockdown Power" with " Instantaneous Charge Stopping Ability " remove the kinetic energy confusion?

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Momentum has the units of slug-ft/s (lb-s) or kg-m/s. Kinetic energy has the units of ft-lbs or N-m. What units does "Instantaneous Charge Stopping Ability" have? Momentum and kinetic energy are core attributes and have have a basis in Newtonian and Einsteinian (General Relativity) physics. Who's physics models does ICSA fit into?

A bullet interaction with matter is easy enough to calculates with today's computers. A homogeneous target material is something a modern personal computer could solve in several hours to a few days with modern Finite Element software and someone that know how to use it and setup the problem **. The problem is you have no way to accurately model a target animal due to the highly variable geometry of the various tissues involved, variability animal to animal, and the highly variable reaction to damage to most of those tissue by individual animals.

Knockdown Power, ICSA, Taylor KO Factor, and the plethora of other empirically derived numbers all have same short coming. If they work at all they only work for a very small range of values/conditions since they are not based on hard physics principals. They are just empirically fitted guess.

** Example: