Why doesn't the .45 look more powerful than the 9mm on paper?

Status
Not open for further replies.
The physics is simple:

The 'force' (linear impulse so one really wants to measure force-time) the person feels from being struck with the bullet is a consequence of the linear momentum. The force felt will be larger or smaller depending on impact time. This is because the linear impulse (which is roughly force times time but better expressed as an integral) is constant and equal to the linear momentum. When tearing into flesh, the impact time is large when compared to hitting a steel plate. Whence, if you were made of steel you would feel a large initial force (which may cause you to lose your balance) but in flesh it is a smaller constant force (constant being a relative term here as we are talking microseconds v. milliseconds).

Hence two objects with the same linear momentum (mass * velocity) depending on how long they impact the target (how long they take to give the target all of their momentum) completely determines how much 'force' is felt.

Such things are readily available in any elementary (Calculus-based) texts on physics. Also see (engineering) texts on dynamics / classical mechanics for more concrete examples.

Edit: I forgot to mention the relationship that force is the time-derivative of (linear) momentum. Hence all the need to talk about multiplying by time.
 
Last edited:
The table posted is for Kenetic Energy; Esubk = 1/2 M*V^2. This formula clearly favors velocity.

Let's try it for momentum; m = M * V

.45 ACP
Ballistic performance
Bullet weight/type Velocity Momentum
165 gr JHP 1060 ft/s 0.78 SFP

185 gr JHP 950 ft/s 0.78 SFP

230 gr JHP 850 ft/s 0.87 SFP



9mm
Ballistic performance
Bullet weight/type Velocity Momentum
115 gr FMJ 1180 ft/s 0.60 SFP

124 gr FMJ 1150 ft/s 0.64 SFP

147 gr FMJ 1000 ft/s 0.65 SFP
Click to expand...

When we use momentum, we see the best .45 ACP load (the 230 grain bullet at 850 fps) has a 34% advantage over the best 9mm (the 147 bullet at 1000 fps.)

Now, what does that mean? Not much -- bullet design and shot placement will over-ride all those numbers.
 
The Holy Writs

Otherwise known as balistic charts, favor speed over heavy profectiles. Run the numbers for a proven stopping round like the .35 Remington, then run the numbers for a smaller but extremely fast cartridge. Marginal diameter but whiz-bang fast always comes out on top. On paper. YRWMMV (your REAL WORLD mileage may vary).
 
All you guys who think the 9 is the same as the 45 look at the Florida FBI shootings. I know, bullets have improved since then... however, 45 bullets didn't get worse and AFIK most of the feebies were using SuperVel ammo and that stuff even in the eighties was very close to the CorBon of the late nineties.
 
Ask the folks who could not stop the Moors (sp?) with .38's, and could with .45 Colts, about bullet diameter and stopping power.

Anyone have bullet weights and velocities on those two loads back then?
 
Why doesn't the .45 look more powerful than the 9mm on paper?
Click to expand...

If you give it some thought, you ought to realize that there are some falacies built into that measurement. People that go around comparing different things with a flawed yardstick are the things I wonder about. :rolleyes:

Read some of the threads on Taylor Knockout Scale - applying it to things Taylor never mentioned. :eek:
 
Uh-oh! Caliber war (again!)

[facetious mode on]

Everybody knows that the 9mm Luger is absolutely harmless. You can shoot yourself or anybody else without any fear of damage whatsoever. Energy and penetration? It means nothing in a 9mm. Just a bogus statistic concocted by ammo companies. The 9mm always bounces off like a spitball fired from a hollow Bic pen.

The .45 ACP on the other hand is always 100 percent lethal. All you have to do is fire a gun so chambered, don't even bother aiming, and any number of BG's get blown 30 feet backwards.

[facetious mode off]

OK, I'm done playing!

;)
 
.45 Colt...?
.38 Long Colt...?
Click to expand...


Sure, let's bring pears and bananas into a discussion about apples and oranges! Think of the nice fruit salad we could make!

FWIW, the .38 Long Colt had a muzzle velocity of generally less than 800 fps:
http://en.wikipedia.org/wiki/.38_Long_Colt

Also it might be pointed out that since the Philippine Insurection was over 100 years ago (1899-1902), it would probably be very difficult to locate someone who could personally attest to the "stopping power" of the sidearms of the day.
 
Why do people use Wikipedia as a reference? This is just a conglomeration of misinformation from a bunch of opinionated idiots. Try using some scientific basis for discussion.
 
Why do people use Wikipedia as a reference? This is just a conglomeration of misinformation from a bunch of opinionated idiots. Try using some scientific basis for discussion.
Click to expand...

:rolleyes:
 
Here print this

All of these tests were done using 10% ballistic gelatin provided by Vyse gelatin using all FBI protocols and 4 layers of denim and two layers of light cotton T-shirt in front of the gelatin.

DoubleTap 9mm+P
115gr. Gold Dot JHP @ 1415fps - 12.00" / .72"
124gr. Gold Dot JHP @ 1310fps - 13.25" / .72"
147gr. Gold Dot JHP @ 1125fps - 14.00" / .68"

DoubleTap .45ACP
185gr Gold Dot JHP @ 1225fps - 12.75" / .82"
200gr Gold Dot JHP @ 1125fps - 14.25" / .88"
230gr Gold Dot JHP @ 1010fps - 15.25" / .95":evil::what:
 
Why do people use Wikipedia as a reference? This is just a conglomeration of misinformation from a bunch of opinionated idiots. Try using some scientific basis for discussion.
Click to expand...
Like the scientifically-designed British encyclopedia I skimmed once? I idly turned to "firearms" and saw an illustration of an M1911, with callouts.

I was somewhat surprised to learn that the part I always called the "magazine" is really called the "handle clip" and that the tip of the grip safety is the "firing pin."
 
Instead of looking at the gross energy of the projectile look at the energy it deposits on or in the target. The .45 deposits the vast majority of its energy on the first thing it hits, the 9mm tends to go through and not deposit as much of its energy.
 
What do people mean by knock down power anyway? Do they mean the potential to inflict a wound that disables a person. I don't see how it is going to "knock" someone down. That Hollywood stuff is bogus. I ran some numbers, a baseball is roughly 148 grams and a 230 gr .45 is 14.9 grams. Immediately one sees that a baseball thrown at 1/10th the speed of a bullet has about the same linear momentum.

Observe 1010 fps ~ 688 mph divide by 10 and you are saying that the 230 gr .45 has the 'knock down' power of a MLB regulation baseball thrown at 68 mph. Doesn't seem like that is going to knock someone off their feet.

An interesting aside, incase you like experimental physics more than theoretical physics, they did an experiment along these lines for mythbusters once. They tried to shoot a dead pig off of a hook with various arms. They could easily knock the pig off with their hand, yet they could not shoot it down. Go figure.
 
I wish we could go a couple of weeks without a .356 vs 11.42mm debate. :banghead:

On double tap's site, you get 550 ft-lbs for 230gr .45, it also quotes 472 ft-lbs for 124gr 9mm +P, and 584 ft-lbs for 125gr .357 sig (9mm on steroids? :p). And the star of the show? 165gr .45, 643ft-lbs out of a 5" barrel.

Momentum is p = m*v

Kinetic energy is Ke = 1/2*m*v^2

In relating momentum to force, you have force = (change in momentum) / (change in time) which is equal to mass x acceleration (the definition of force is mass x acceleration). Acceleration is equal to 1/2 times the velocity squared. That's why the use of 1/2*m*v^2 is applicable to this debate, and m*v is not. Besides, are we going to argue that a 230gr .45 has more power to it than a .223? No, cause that's just crazy talk!

I personally don't think there's a huge difference between the two. And since when is the average Marine in Iraq being issued a 1911? Does everybody get this into the debate between .357 magnum and .45? Same size debate essentially, but no one seems to argue the .357magnums stopping power. Why not!? Cause it doesn't sound wimply like 9mm? From now on, .357 sig will be called 9mm MAGNUM! :neener:
 
9mm vs 45

More mass at a lower speed = bug hitting the windshield.
 
Status
Not open for further replies.

Similar threads

cluttonfred
  • Locked
Was Johnson right... bring back the .22 Spitfire?
Replies
14
Views
7K
M2 Carbine
M
D
  • Locked
Wow! Buffalo Bore beats .357 Sig in .38 Spl?
Replies
7
Views
1K
Deaf Smith
Deaf Smith
P
  • Locked
Why are the handgun bullets heavier rifle bullets?
2
Replies
35
Views
2K
mboylan
M
S
  • Locked
Range Report: Glock 26...
2
Replies
33
Views
2K
Stephen A. Camp
S
S
  • Locked
A Layman's Look: Winchester RA45T, PowRball, & Rem GS...
Replies
15
Views
1K
Stephen A. Camp
S
Back
Top