Stopping Power - Knock Down Power

[10ring]

You just gotta love it. In response to the question "It’s been stated everywhere that there is no such thing as Stopping Power or Knock Down Power. So that being the case, what DO you call it?

We get.....

AhhhUgggg. I said I'll stop, but I'll show you the numbers. I did these off the cuff.

Assumptions.
40 grain .22 lr traveling at 1,000 f/s.

A child rolling a 6 lb bowling ball at 10 mph (14.6 f/s) when it hits the pin - It will probably still knock down a pin even at 5 mph, but lets use 10 mph. The ball has a radius of 4.25" or .375 feet.

For the bullet the momentum is m*v where m is in slugs and v is in f/s. To convert 40 grain to slugs m=40/7000/32.2 = .000177. The momentum = .000177*1100 = 0.195 slug-ft/s.

The KE of the bullet is .5*m*v^^2 = .5*.195*(1100^^2) = 107 ft-lb.

The total momentum of the bowling ball = the transitional momentum + angular momentum. Transitional momentum = m*v. Angular momentum = Inertia (I) * Angular Velocity (w)

The mass of the bowling ball is 6/32.2 = .186 slugs. The Transitional Momentum is .186*14.6 = 2.72 slug-ft/s.

I = 2/5*m*r^^2 = 2/5*.186*(.354^^2) = .009 slug-ft^^2

w = v/r = 14.6/.354 = 41.2 rad/sec

Transitional momentum = 2.72 + .385 = 3.11 slug-ft/s

The bowling ball kinetic energy = Transitional KE + Rotational KE = .5*m*v^^2 + .5*I*w^^2

Trans KE = .5*.186*(14.6^^2) = 19.9 ft-lb
Rot KE = .5*.009*41.2 = 7.94 ft-lb
Total KE = 27.8 ft-lb

Bottom line...
A .22 with 107 ft-lb of KE and .195 slug-ft/s of momentum can't knock down a bowling pin, but can damage it.

A 6 pound bowling ball rolled by a child at 10 mph with 27.8 ft-lb of KE and 3.11 slug-ft/s of momentum can knock down a bowling pin and won't damage it.


I didn't double check the numbers, but I think they close. Like I said, I'm done.

No offense intended to poster of this.

 

[Ziggy2525]

You just gotta love it. In response to the question "It’s been stated everywhere that there is no such thing as Stopping Power or Knock Down Power. So that being the case, what DO you call it?

We get.....



No offense intended to poster of this.

You want a simple answer to a complex question and it doesn’t exist. A somewhat simple answer was given and someone said “show me the calcs,” so that’s why the calcs post.

Here’s the somewhat simple answer again.

Stopping power and knock down power don’t exist with service caliber pistol rounds. Pistol rounds don’t have enough momentum to knock normal sized people over or enough kinetic energy to blow them apart.

Once you get outside pistol rounds, the momentum from an 6lb cannonball traveling at 200 f/s will knock you down right now. The kinetic energy from a .50 bmg traveling at 2800 f/s will blow you apart and stop you in your tracks (videos on youtube from Iraq/Afghanistan). Those rounds have both knockdown power and stopping power.

 

[fredj338]

I am a member of a group that shoots bowling pins with .22 lr handguns. We knock bowling pins down, and off of the table, with .22s every time we meet.

BE fare though, in 22lr pin shoot the pins are on the back of the table. With centerfire, on the front of the table, BIG diff.

 

[hkcavalier]

Pin shooting is a pure example of "knockdown power" and after, what, 40 years is well sussed out. You need big bullets at modest velocities, at a minimum. The stage where they just have to fall down when hit (not clear the back of the table) only needs a 9mm doublestack. I'm sure some guys have tried guns like the PMR-30 or even FN57, since you just need enough power to make the pin fall over.

None of which has anything to do with stopping an attacker, unless of course he's made of wood and stands on a table. As this is an unlikely scenario for any of us, what are we arguing about?

 

[Fastbolt]

Folks, knocking over a lightweight plastic clad wooden bowling pin is not in the same realm as causing a 2 or 4 legged mammal to be knocked off its feet.

Stopping someone from being physically able to continue their volitional actions due to GSW is typically dependent on the nature of the critical tissues, structures and organs damaged by the GSW (and the number of GSW's delivered, the rapidity of their placement, etc).

Unconsciousness via exsanguination, CNS damage and inability to remain conscious and/or exhibit physical control, structural (skeletal/muscular) degradation, etc are all physiological issues. Now, psychological causes and effects are even more unpredictable.

Back in the days of the original FBI studies one of the things decided (by them) was that "only falling down" when someone was shot was good ... presuming the person falling down due to GSW wasn't still able to continue shooting at you from that prone or supine position after falling down.

"To judge a caliber’s effectiveness, consider how many people hit with it failed to fall down and look at where they were hit. Of the successes and failures, analyze how many were hit in vital organs, rather than how many were killed or not, and correlate that with an account of exactly what they did when they were hit. Did they fall down, or did they run, fight, shoot, hide, crawl, stare, shrug, give up and surrender? ONLY falling down is good. All other reactions are failures to incapacitate, evidencing the ability to act with volition, and thus able to choose to continue to try to inflict harm."

http://gundata.org/images/fbi-handgun-ballistics.pdf

It's not at all a bad idea to go back and consider the issues raised and discussed in Handgun Wounding Factors and Effectiveness now and again.

It probably beats trying to decide how slapping a lightweight metal target or wooden bowling pin might somehow translate in "stopping power" or "knock down power" when applied to human attackers ... and common defensive/service handgun calibers.

This is more important than choosing a professional sports team, brand of truck or just liking the way some brand of JHP looks prettily mushroomed after impacting organic or synthetic gel blocks (or water bags in a box, bottles, cans or whatever other informal "testing" someone may favor).

We can run "test mediums" all day long and look to see and admire what the mediums do to the bullets in the way of deforming and expanding them.

Things became "a bit less simple" when trying to predict what GSW's do to people ... and how the people suffering the GSW's may do in the way of reaction and response.

How about wondering if the intended victim needing to shoot a gun in self defense is even up to the task of actually putting the bullets on the intended threat target in an accurate, controllable and (perhaps) sufficiently repeated fashion?

Physical fights can be messy, chaotic and can change in the blink of an eye. What makes anyone think a gun fight is going to be any different?

Perhaps less distraction on caliber and the adoption of terms bordering on looking at something from the perspective of it being almost a "talisman", and more focus on using the best tool available for the individual, in the most practical, skilled and effective way possible?

 

[Ribwizzard]

When did we start talking about human targets?
Thought we were talking about squirrels & coons?

 

[swsig]

Momentum Disruption -- A Better Term?

Here's a copy of a post I made in the Ammo forum in a thread about the usefulness of the .45 acp round. In that thread, I proposed using an alternate term, "Momentum Disruption":

"

What I would really like to see discussed here today is the .45 ACP and nothing more. Not how it compares to other cartridges, just the .45 ACP cartridge on its own, something that nobody can ever seem to do anymore.

In this thread, let's discuss the merits of the .45 ACP cartridge, it's strengths, what it's good for, where it shines, and how it's still relevant today.

Getting back to your original question, here is some actual data. I hope this helps.

One of the range officers at my range is a retired homicide detective from a major city PD. One of his duties was to investigate every officer-involved shooting. He asked every officer how the bad guy reacted when he was hit. Across many such interviews, three rounds emerged as momentum disruptors. (That's my term. I don't want to get into the well-worn "stopping power" and "knock down power" debate.) These three rounds all caused the subjects to lurch backward when hit in the torso, at least temporarily disrupting whatever they were doing. One of these momentum disrupting rounds was the .45 acp.

(Just as an FYI, the other two were the .357 mag, and the .357 SIG. Notably, the 9mm round created little or no momentum disruption.)

So there it is. Although it is a small sample study, it is based on real-world observations of actual shootings made by trained professionals. No gel, no animal analogs, just reality. Take it for what it is worth, and do what you think is best for you. In my case, I've given up 9mm, and carry .45s. YMMV."

 

[Gamecock]

"The only sure stopper is a supersonic telephone pole." - Skeeter Skelton

 

[Walkingwolf]

It’s been stated everywhere that there is no such thing as Stopping Power or Knock Down Power.

So that being the case, what DO you call it?

It's all relative to the target. Stopping power can be just the display of a firearm. Knock down power is certainly a factor when shooting knock down steel targets, or bowling pins.

Everybody forgets popping power caused by the heat used to make popcorn pop for use in certain threads. There also is boiling power for the size stove used to make iced tea to be consumed with the popcorn.

 

[mrchuck]

Dis-erupting the brain or spinal cord is the only way to have a human collapse immediately when shot with your handgun.
Being blown backward is Hollywood Ballyhoo.

 

[Ribwizzard]

Everyone seems to have a different definition of stopping power and knockdown power, try to talk about the kinetic energy of the projectile and someone else is wanting to talk about wound cavities and shot placement. To me, it's the energy of the projectile before it hits the target. The potential that it has to apply force. There are too many variables to measure it by what happens to the target. That would be rating the target at its ability to deflect the energy.

 

[10ring]

You want a simple answer to a complex question and it doesn’t exist. A somewhat simple answer was given and someone said “show me the calcs,” so that’s why the calcs post.

Here’s the somewhat simple answer again.

Actually, I didn't ask anything, I was just commenting on the thread. I gave a simple answer early on in the thread that said calling it stopping power was fine.

There are so many variables involved in any defensive shooting scenario involving a normal defensive handgun that mathematical calculations about one caliber or the next don't provide any useful answer.

In regard to defensive handgun ammunition and its possible effect, kinetic energy is meaningless.

 

[10ring]

Folks, knocking over a lightweight plastic clad wooden bowling pin is not in the same realm as causing a 2 or 4 legged mammal to be knocked off its feet.

Some people fall over when shot simply because their brain thinks they should (a rather unscientific way of describing the effect of psychology in any defensive shooting).

 

[ImprovedModel56Fan]

Its simple, we know a .44 mag will knock down a bowling pin , whereas a .22 wont becouse the .44 mag carries more kinetic energy
It is measurable and real

False. While a .44 Mag will almost always knock down a bowling pin, and a .22 LR almost always won't, it's not because one has more kinetic energy.

Luminosity is measurable and real, but it has very little to do with knocking down bowling pins.

Furthermore, NO handgun cartridge has knockdown power effective on humans. See posts above.

 

[ImprovedModel56Fan]

You just gotta love it. In response to the question "It’s been stated everywhere that there is no such thing as Stopping Power or Knock Down Power. So that being the case, what DO you call it?

We get.....



No offense intended to poster of this.

You may not like the answer, but I'm not all that crazy about the question. What do you call WHAT? The OP asks what you call "it," after naming two different concepts, one often misunderstood, the other non-existing in self-defense scenarios not involving a rabid mouse. The problem isn't what you call those two different concepts, rather what mistaken notions you have about them.

Many of the answers, probably including the one you didn't like, attempt to answer the deficiencies exposed by the original question. Many answers were useless or misleading because the poster didn't know the difference between KE and momentum, and had little idea of whether either applied to what may have been under discussion.

 

[Gamecock]

Dis-erupting the brain or spinal cord is the only way to have a human collapse immediately when shot with your handgun.

BUT !!! the objective is to get the bad guy to stop doing what he's doing. It doesn't have to be physical, though a CNS shot can be.

I have long thought that the effectiveness of the .357 - stopping power - is just how damn loud it is. The bad guy doesn't want to hear that again! Especially being down stream from it.

 

[Kanewpadle]

Wow, I didn’t realize this would get so complicated.

Since people claim that stopping power does not exist with a handgun, what term would you use?

Personally I think Stopping Power is an adequate term to use instead of the term Knock Down Power. We have to call it something. Or should we just make up another term and call it good?

Not interested in kinetic energy, wound channel, temporary or permanent cavity. Those terms are BS. They do nothing to incapacitate an attacker in a quick manner.

 

[Muss Muggins]

Does the FBI know this ? ? ?

 

[Ziggy2525]

Wow, I didn’t realize this would get so complicated.

Since people claim that stopping power does not exist with a handgun, what term would you use?

Personally I think Stopping Power is an adequate term to use instead of the term Knock Down Power. We have to call it something. Or should we just make up another term and call it good?

Not interested in kinetic energy, wound channel, temporary or permanent cavity. Those terms are BS. They do nothing to incapacitate an attacker in a quick manner.

The terms Stopping Power and Knock Down Power are made up terms that don’t have a measurable basis. I don’t think you need to make up a new term. Momentum already exists and in this context is the measure of bullet “wallop.”

 

[6518John]

Reading this thread would incapacitate about anyone. I am going to carry it and hand it over to any attacker and tell them “you read this and work these formulas you can have my wallet, car and house too! But if you expect me to read this again—please shoot me and put me out of my misery.”