What is "Knockdown"?

[jimlongley]

Just finished reading one of the later "Bourne" novels, and boy did I have to work to stay at it.

Firing bursts from semiautomatic machine guns;

A .45 firing at contact range grazes a victim, tossing him into the next room;

An other gaffes too numerous to mention.

[The Annoyed Man]

A "pocket" shotgun?.....

That's kind of what I was thinking.

[WildBill]

The point of all this is that, as WildBill said, a "combat" mindset will get you through an amazing amount of trauma, so long as your wounds are not instantly fatal, and even a direct hit to the heart may not be necessarily instantly fatal. Where I would disagree is that it may be possible that temporary incapacitation has nothing to do with the combat mindset, while the ability to recover from temporary incapacitation ...

There is no disagreement on my part. Of course, I am over simplifying. I agree that any kind of physical trama can temporarily incapacitate. Mental shock or surprise can also cause people to freeze.

I have read a little about Texas DPS liking the .357 Magnum for it's "lightning bolt effect." There isn't much that I can find on the internet whether they it considerate it purely a physiological effect or partially psychological. I know that the muzzle blast and the crack of a .357 round gets my attention.

[LedJedi]

I'm thinking if knockdown is really your goal you're better off going with one of these than a .45.



:)

[Texian]

Watch this movie, Last Man Standing w/ Bruce Willis, to see Hollywood version of .45 ACP knockdown (and move around) power.

http://www.imdb.com/video/screenplay/vi1435631897/

[paadams]

I downloaded a FBI document from glocktalk.com regarding this very issue. It was written by the FBI in '89 but everything in still stands today. I have it on my laptop which is it at work or I would quote a few things from it. It's 19 pages and very informative. As stated by previous posters there is no such thing as "knockdown" power. Anything capable of knocking someone down on impact would knock down the shooter as well. The only thing that could really be relied upon to stop an attacker is damage to the central nervous system or extreme loss of blood.

Anyone intrested in the FBI document can PM me with your email address and I can email it to you. Unfortunaly I didn't save the original link to repost, only saved the document.

Pete

[lrb111]

This might have been it. http://www.firearmstactical.com/hwfe.htm
More links here. http://www.firearmstactical.com/wound.htm

[Excaliber]

it is unrealistic to expect that our "puny" 1911s, etc., are going to knock anybody down.

Great ER story. There are lots like it, too.

The laws of physics (action and reaction) state that of a bullet were capable of physically knocking someone down from energy transfer alone, recoil would have the same effect on someone of the same size at the launcher end. That would not be a good thing, but no reasonably portable handgun comes close to this level of power. So forget about knockdown with handguns. If a subject is immediately taken out of action with a shot, it's because of things other than energy transfer alone. There are no magic bullets.

That being said, history shows us that some weapons produce quicker and more frequent threat stops with fewer shots than others. The two very rough rules of thumb here (assuming hollowpoint ammunition is used) are: "Bigger is better" and "Smaller and really fast can be just about as good if the projectile expands" - a big if. There's lots of intellectually interesting controversy around the details for particular given loads and some might rephrase the "rules" the other way around, but you wouldn't go far wrong if you accepted these as general guidelines for purposes of selecting a defensive weapon.

Bullet placement is much more important than caliber, especially when we're looking at .38 caliber and above. Solid central nervous system hits are immediate fight stoppers. Critical skeletal structure hits (e.g. pelvis) are mobility stoppers, but not necessarily fight stoppers. Major organ and blood vessel hits are eventual fight stoppers. How quickly they take effect depends on how quickly enough blood loss occurs to induce hypovolemic shock and unconsciousness due to lack of oxygenation to the brain. This involves lots of variables. Psychological stops also happen when the wounded person realizes he's shot and thinks he should be disabled, even though he's physically capable of continuing action.

Something that doesn't apply to most carry handguns but does apply to rifles like the .308 and could apply to some specialty hunting pistols is that rifle velocity rounds (2000 fps+) create a hydrostatic shock wave in tissue that damages organs not touched by the projectile. The faster and bigger the round, the greater this effect becomes (not to mention the fact that they carry a lot more terminal ballistic energy than handgun rounds.) This phenomenon makes them much more effective fight stoppers than handguns when they're available.

So you don't need to ditch that 1911 - you're already armed with one of the most proven fight stoppers available, to the extent that's possible. You also wouldn't be badly armed with a .40 with more shots before a reload. But don't be surprised if you don't see instant one shot stops with either one. I also wouldn't advise going out without spare magazines. Better to have that ammo and not need it than the other way around.

[pt145ss]

it is unrealistic to expect that our "puny" 1911s, etc., are going to knock anybody down.

The laws of physics (action and reaction) state that of a bullet were capable of physically knocking someone down from energy transfer alone, recoil would have the same effect on someone of the same size at the launcher end.

I agree with most everything except the statement above. I agree that for every action there is an equal and opposite reaction. However, some of that opposite reaction can be reduced mechanically so that it has less of an effect on the "launcher." For example, take an AT4 or LAW (lite antitank weapon), I would assume that it would have enough velocity and mass to "knock down" a human target...however, the human "launching" the projectile feels little or no effect from the oppsosite reaction as it blows out the back.

[The Annoyed Man]

it is unrealistic to expect that our "puny" 1911s, etc., are going to knock anybody down.

The laws of physics (action and reaction) state that of a bullet were capable of physically knocking someone down from energy transfer alone, recoil would have the same effect on someone of the same size at the launcher end.

I agree with most everything except the statement above. I agree that for every action there is an equal and opposite reaction. However, some of that opposite reaction can be reduced mechanically so that it has less of an effect on the "launcher." For example, take an AT4 or LAW (lite antitank weapon), I would assume that it would have enough velocity and mass to "knock down" a human target...however, the human "launching" the projectile feels little or no effect from the oppsosite reaction as it blows out the back.

Granted... but if the exhaust didn't blow out the back (and it doesn't in a firearm), an AT4 or LAW would flatten you on firing. It is exactly because the rocket exhaust vents out the back that the shooter is not subjected to the same action/reaction laws. On the other hand, a rocket launcher isn't really a concealable firearm.

[paadams]

This might have been it. http://www.firearmstactical.com/hwfe.htm
More links here. http://www.firearmstactical.com/wound.htm

Thanks for the link! I've been looking for another. Was so mad at myself for not saving the link and only the document.

[Excaliber]

This might have been it. http://www.firearmstactical.com/hwfe.htm
More links here. http://www.firearmstactical.com/wound.htm

Thanks, lrb111, for sharing the links to this authoritative reference material.

There's plenty of meat to chew on there for folks who really want to gain solid knowledge on wound ballistics and what it means for self defense.

[pt145ss]

Granted... but if the exhaust didn't blow out the back (and it doesn't in a firearm), an AT4 or LAW would flatten you on firing. It is exactly because the rocket exhaust vents out the back that the shooter is not subjected to the same action/reaction laws. On the other hand, a rocket launcher isn't really a concealable firearm.

You are right...it does not blow out the back in a firearm. The energy is disipated in other ways...like noise and forcing the slide back and chambering the next round.

The point was...you can't use the fact that the "launcher" is not knocked down as proof that a bullet does not have knock down power...it has to be proved in other ways.

[Excaliber]

The point was...you can't use the fact that the "launcher" is not knocked down as proof that a bullet does not have knock down power...it has to be proved in other ways.

I think the burden of proof here runs in the other direction.

The fact that lots of people shot with handguns (and even sometimes by rifles and shotguns) don't fall down should meet the requirement for proof. Although as one member pointed out, semiautomatics dissipate a small amount of energy with the recoiling slide, this is not the case with revolvers. Folks shot with revolver bullets don't fall down all the time either, as they would if sufficient energy were transferred by the projectile. When they do fall, it's because of other factors at work as detailed in the FBI "Handgun Wounding and Effectiveness Report" report (http://www.firearmstactical.com/hwfe.htm), which is only 12 pages long and very well written. It explains clearly and in detail what to expect from handgun fire, and what factors increase the desired effects.

Page 12 of the FBI report puts it this way:

"The impact of the bullet to the body is no more than the recoil of the weapon. The ratio of bullet mass to target mass is too extreme."

"A ten pound weight equals the impact of a .45 when dropped from 1.37 inches (achieving a velocity of 2.71 fps)."

"A bullet simply cannot knock a man down. If it had the energy to do so, then equal energy would be applied against the shooter and he too would be knocked down. This is simple physics and has been known for hundreds of years."

In this case, I realize that being exposed to the facts can create some cognitive dissonance and disbelief. The facts conflict with a lot of bad information that's widely distributed in print, and some folks may continue to believe that handgun bullets carry enough energy to knock a person down despite rock solid evidence that they don't. People come to accept new things in many ways, and some folks just have to see, touch, feel, smell and taste something themselves before they'll believe it. (The "Missouri" approach). Learning these lessons during a deadly force confrontation is the hard way to go, but it is really convincing.

[pt145ss]

The point was...you can't use the fact that the "launcher" is not knocked down as proof that a bullet does not have knock down power...it has to be proved in other ways.

I think the burden of proof here runs in the other direction.

The fact that lots of people shot with handguns (and even sometimes by rifles and shotguns) don't fall down should meet the requirement for proof. Although as one member pointed out, semiautomatics dissipate a small amount of energy with the recoiling slide, this is not the case with revolvers. Folks shot with revolver bullets don't fall down all the time either, as they would if sufficient energy were transferred by the projectile. When they do fall, it's because of other factors at work as detailed in the FBI "Handgun Wounding and Effectiveness Report" report (http://www.firearmstactical.com/hwfe.htm), which is only 12 pages long and very well written. It explains clearly and in detail what to expect from handgun fire, and what factors increase the desired effects.

Page 12 of the FBI report puts it this way:

"The impact of the bullet to the body is no more than the recoil of the weapon. The ratio of bullet mass to target mass is too extreme."

"A ten pound weight equals the impact of a .45 when dropped from 1.37 inches (achieving a velocity of 2.71 fps)."

"A bullet simply cannot knock a man down. If it had the energy to do so, then equal energy would be applied against the shooter and he too would be knocked down. This is simple physics and has been known for hundreds of years."

In this case, I realize that being exposed to the facts can create some cognitive dissonance and disbelief. The facts conflict with a lot of bad information that's widely distributed in print, and some folks may continue to believe that handgun bullets carry enough energy to knock a person down despite rock solid evidence that they don't. People come to accept new things in many ways, and some folks just have to see, touch, feel, smell and taste something themselves before they'll believe it. (The "Missouri" approach). Learning these lessons during a deadly force confrontation is the hard way to go, but it is really convincing.

I agree...currently there are no handgun calibers that have the right combination of mass and velocity to knock down a human. I also agree that physics dictate that when all things are relative…that there will be a backward force put against the shooter that is equal to the force pushing forward.

What is not being accounted for in using this as an argument are the things that are not relative like biomechanics. You use a revolver as an example. Even with a revolver, not all the backward force if being applied directly to the shooter. Some of the force is being expelled out the sides, some of the force is used to break the wrist, elbows, and shoulders from their locked position. Some of the force is being used to force the arms and weapon in a slight upward motion. All of which disipate and redirect the force being expelled back toward the shooter.

If you had a way to keep everything locked and in line so that all the rearward force was applied directly to the shooter, I think that you would find that the rearward pressure is much greater then than what you feel given all the ways the force is dissipated during the recoil. Again...I don't think it would be enough to knock the shooter down...but it would be closer.

Given the example I gave with the AT4 and LAW…it most definitely has the right combination of mass and velocity to knock down a human target…but because it transfers almost zero backward force directly to the shooter…shooter has less felt recoil than that of a handgun. Trust me…I’ve shot enough of them to know...(back blast area all clear!!! Whoaah!!!).