9mm vs .45ACP

[Lost Sheep]

"Knock down power" gets people riled up because people have two different meanings in mind. One possible meaning (the most literal) is that the force of impact of the bullet physically pushes a person off his or her feet to the ground. The second possible meaning is the ability of the round to cause a person to become incapacitated immediately.

The first is hollywood nonsense. Momentum is conserved, and Newton's Third Law still applies at human scales. If the bullet's impact alone has the power to knock down the target, its recoil has the power to knock down the shooter. (Admittedly, just a light shove can topple someone if you catch them at just the right point in their stride and/or they're already off-balance, a bullet with a lot of momentum can do the same... the same is true, of course, for the shooter. But that's a rare instance, and not what people are imagining.) This is the meaning that gets scientifically-minded people into a frenzy, because it's just fictional.

The second meaning is what (intelligent) people actually using the term more often mean. And that, of course, raises all the questions that terminal ballistics always raise, such as differing theories of wounding and incapacitation. It's almost a philosophical argument...

I disagree with your term, "philosophical", but agree totally with your position.

The physiological aspects of the vague term "knockdown power" are very real, physical phenomena. Pain, temporary wound cavity, nerve damage, even temporary nerve signal disruption.

The psychological aspects are less relliable, but still real. The sound of the shot, the flash, muzzle blast, sometimes just the knowledge that one has been shot or is merely being shot at is enough to stop someone in their tracks. Not technically "knockdown", but stopping (sometimes).

Just my philosophical take on it.

Lost Sheep

 

[verdun59]

Wow, I'm knocked down by this civil discussion of the never ending debate. I had popcorn ready and was going to reach for a beer ..... what's happened to the usual crowd, must be on vacation.

 

[spotch]

Wow, I'm knocked down by this civil discussion of the never ending debate. I had popcorn ready and was going to reach for a beer ..... what's happened to the usual crowd, must be on vacation.

Oh YEAH?!? You got a problem with the discussion?! How about I knock you down!?!?

 

[RBid]

Personally, I get knocked down, but I get up again. They're never gonna keep me down.

/duck

 

[76shuvlinoff]

I agree but that 1911 sure fits easy in the nightstand.

It sure does, 3 steps from the 870 too.

These days most of my carry is a pocket .380 loaded with FMJs but for over a year I have really been contemplating a slim single stack 9mm. This thread has me sold on following through with that search.

FWIW "Knockdown" to me indicates the dispensing of a 12ga slug.

 

[jimbo555]

I wonder what the 200gr.45acp+p gold dot would look like in comparason?

 

[RBid]

200gr +P Gold Dots did extremely well in tnoutdoors9's denim + gel test. It's worth checking out on YouTube.

 

[CDW4ME]

Knock down power / momentum

I'm not sure that momentum is the best (sole) indicator of handgun performance.

I use this short formula to determine momentum:
projectile weight x projectile velocity = ______ / 225120 = momentum

Here are some handgun examples (food for thought / discussion):

My chronographed averages for 5 shots:
230 gr. Ranger T out of a Glock 30 @ 874 fps / 390# KE / .89 momentum
125 gr. Ranger T out of a Glock 32 @ 1,340 fps / 498# KE / .74 momentum

If we determined handgun effectiveness using momentum, then the 45 acp (in that example) is clearly better (17%); however, according to KE the .357 Sig is "more powerful" (22%).

Rifle example:
From my 16'' Stag 2T .223 using a 60 gr. Nosler Partition handload:
60 gr. @ 2,807 fps / 1,050# KE / .75 momentum

Additional example with observed results :

My wife shot an average size 8 pt. buck last december; she used a .50 caliber blackpowder rifle loaded with a saboted 45 cal JHP pistol bullet.
The deer was about 15 yards away when she shot him from a blind. The bullet entered just behind the shoulder went through both lungs, penetrated bone on the offside shoulder and lodged under the hide on the opposite side, perfect placement. I could see the lump under the hide and only had to make a slit to get the bullet which had mushroomed to about .60

I had loaded her rifle with just over 90 gr. of Pyrodex launching that 260 gr. bullet at an estimated (never chronographed it, based on load chart) 1,300 fps.

260 gr. 45 cal bullet @ 1,300 fps / 976# KE / 1.50 momentum

Even though the buck was hit perfectly by a high momentum projectile he was not knocked off his feet; he kicked up his back legs, and ran for about 40 yards before falling.

 

[Kleanbore]

I'm not sure that momentum is the best (sole) indicator of handgun performance.

It isn't. Nor has anyone said otherwise.

If we determined handgun effectiveness using momentum, then the 45 acp (in that example) is clearly better (17%); however, according to KE the .357 Sig is "more powerful" (22%).

According to the FBI, the best indicator of handgun projectile performance is penetration, followed by bullet diameter. See this. Kinetic energy is one determinant of penetration.

Even though the buck was hit perfectly by a high momentum projectile he was not knocked off his feet;...

...which explains perfectly why the shooter was not knocked down.

 

[481]

Knock down power / momentum

I'm not sure that momentum is the best (sole) indicator of handgun performance.

I use this short formula to determine momentum:
projectile weight x projectile velocity = ______ / 225120 = momentum

Here are some handgun examples (food for thought / discussion):

My chronographed averages for 5 shots:
230 gr. Ranger T out of a Glock 30 @ 874 fps / 390# KE / .89 momentum
125 gr. Ranger T out of a Glock 32 @ 1,340 fps / 498# KE / .74 momentum

If we determined handgun effectiveness using momentum, then the 45 acp (in that example) is clearly better (17%); however, according to KE the .357 Sig is "more powerful" (22%).

Rifle example:
From my 16'' Stag 2T .223 using a 60 gr. Nosler Partition handload:
60 gr. @ 2,807 fps / 1,050# KE / .75 momentum

Additional example with observed results :

My wife shot an average size 8 pt. buck last december; she used a .50 caliber blackpowder rifle loaded with a saboted 45 cal JHP pistol bullet.
The deer was about 15 yards away when she shot him from a blind. The bullet entered just behind the shoulder went through both lungs, penetrated bone on the offside shoulder and lodged under the hide on the opposite side, perfect placement. I could see the lump under the hide and only had to make a slit to get the bullet which had mushroomed to about .60

I had loaded her rifle with just over 90 gr. of Pyrodex launching that 260 gr. bullet at an estimated (never chronographed it, based on load chart) 1,300 fps.

260 gr. 45 cal bullet @ 1,300 fps / 976# KE / 1.50 momentum

Even though the buck was hit perfectly by a high momentum projectile he was not knocked off his feet; he kicked up his back legs, and ran for about 40 yards before falling.

Just as it is with kinetic energy, so it is with momentum. The "raw numbers" mean nothing 'til something is hit.

Tissue damage in the right place is what brings about incapacitation/death.

Of course, the deer wasn't knocked down. Even if the deer weighed only 125 pounds, its resultant velocity would be on the order of just a few inches per second, 4.634 inches per second to be exact, assuming that the bullet remains, as it did, within the animal- not enough to knock the deer down by any stretch of the imagination.

 

[silversport]

Your gelatin results are to be expected, as both cartridges were not only made by the same company, for the same purpose, but were designed to do the same thing, to the same protocols as most premium JHPs produced by all the major manufacturers for the common duty cartridges. A .40 Gold Dot from my duty P229 would perform the same. One 9mm Winchester Silvertip, fired by FBI Special Agent Dove, into a certain Mr. Platt, circa 1986, has led to this, as that shot was deemed to have not penetated deeply enough.

I work for a very large PD, one of the largest in the USA, and we collectively shoot quite a few bad guys, over time. Until 1997, we carried a range of duty cartridges, in personally-owned duty pistols. Since 1997, the newer officers' primary duty pistols, while still officer-owned, have all been chambered for the .40 S&W, as have all the newer pistols bought my the pre-1997 veteran officers. While I do not have access to the terminal ballistic data, nor the incident reports, the long-term general knowledge among street officers around here is that shot placement is paramount, and all the duty cartridges perform about the same. When we hit bad guys in the important bits, they go down. When we miss the important bits, they may or may not go down. Of course, some officers, whose shots did not stop bad guys, tend to blame the ammo, when, really, the officers missed the most important bits.

Yup...+1

Bill

 

[Skribs]

http://ammo.ar15.com/project/Self_Defense_Ammo_FAQ/MiscDocuments/HandgunBulletchartaspicturerev3.jpg

Here is an interesting chart - note that with the introduction of heavy clothing, it changes how the wound tracts differ from each other. I wonder how different the results would be with clothing or fake bone.

Another thing to note about the OP is we're comparing 9mm +P in a 4" barrel to .45 "short barrel" ammo in a 3 3/4" barrel (rounding slightly on both). This means we actually have a bit more power going into the 9mm than the .45, by comparison.

This is an interesting comparison, but it doesn't exactly highlight the differences between the two, because we have different variables introduced besides simply 9mm and .45.

 

[chuckpro]

The thing i love about people talking about knock down power is Newton's 3rd law of motion. If the gun doesn't Knock you down when you shoot it how is it going to knock down your target, maybe take down would be more appropriate. I know this is simplified and you have to consider force over time. Just thought i would add my two cents.

 

[HammerheadSSN663]

I'm glad your test shots were conducted at 'almost' the same time.

 

[coalman]

9mm fans rejoice. 9mm = .45acp. One backyard test, of one bullet each, puts this to rest for good indeed.

Which was fired into the block first?

 

[918v]

45 shoots lead bullets better, so there.

 

[joneb]

The .45 came from the right, the 9mm came from the left. No clothing, 5 feet distance. The 9mm penetrated to 12 inches, the .45 penetrated to 12.25 inches.

Neither have adequate penetration. I would use FMJ for SD over the loads in the test.

 

[mavracer]

Neither have adequate penetration. I would use FMJ for SD over the loads in the test.

Not sure how you could say that for sure without calibrating the block.

 

[WinThePennant]

Using the phrase "Knock down power" is the new way of getting an Internet slap-down.

Back in the day, it was using the term "clip" would you should have used the term "magazine."

 

[M7]

Using the phrase "Knock down power" is the new way of getting an Internet slap-down.

Back in the day, it was using the term "clip" would you should have used the term "magazine."

Yep, just like all "buzzwords", such terms are rarely defined, but thrown about like everyone oughtta know what they mean.

"Knock-down power", "stopping power"- without concensus as to what they mean, they are useless terms that produce more confusion than answers.

 

[M7]

Not sure how you could say that for sure without calibrating the block.

I think he's just expressing his preference. Even if they results are accurate, it is too little penetration for me, too. I like my ammo to penetrate in the 16 inch (give or take a couple inches) range.

 

[willypete]

Neither have adequate penetration. I would use FMJ for SD over the loads in the test.

What, exactly, are you planning on defending against?

 

[joneb]

What, exactly, are you planning on defending against?

It's really hard to say.
It's better to have more than not enough.

 

[C0untZer0]

You'll still get an Internet slap-down if you use the word clip (unless you're actually referrring to a real clip)

And my favorite slap-down is when I say slide release... I know I'm gonna get a slap-down but I say it anyway

 

[Skribs]

I actually just ordered a clip for my XDm.
Well, a tuckable belt clip for my holster for my XDm

Jibjab, while you're right - more is better than less - 12" is the FBI minimum requirement. I'd rather have a wide wound tract that is rated as penetrating at least enough than a narrow wound tract that will penetrate more.