Does velocity matter?

The momentum/kinetic energy discussions here on TFL remind me of the horsepower/torque discussions on automotive boards. In both cases, you've got two related physical quantities (related in the sense that the quantities that determine one of them also appear in the equations that determine the other one.) And in both cases, the debate rages onward through the years.

For my money, I agree that a bullet's kinetic energy is a better predictor of potential tissue destruction than its momentum. As an example, a major league fastball has 30% more momentum than a 230 gr .45 ACP slug, but it's not going to cause nearly as much tissue damage (even accounting for the different size/shape of the projectile.)

But I can't think of a projectile with the same kinetic energy as the .45 slug that's not going to cause serious injury (unless you consider something very large and very slow, like a multi-ton truck moving at 1-2 MPH.)

And since velocity is a quadratic term in the kinetic energy equation, I'd say yes, velocity matters - a lot.
 
Most of the discussion has missed the historical relationship between the 357mag and the round it replaced, the .38 Special. The 38 special would gently cause the police popular 148 gr wad cutter to scoot along at a brisk 690 ft/s. The 357mag would launch the popular 125gr JHP along at a then astounding 1600ft/s.

Adding a 150% more velocity made wonderful things happen (from the perspective of the police). Bullets that used to bounce off of car windshields were going through and hitting/killing the perp. Perps, when hit would wilt, lay quivering and expire contrasted with the .38 where they would frequently continue running and shooting back. That dramatic terminal improvement is what made the 357 such a popular round and gave it the cult following with all that urban myth BS like breaking engine blocks, etc.

In historical context, the bullets of the day were also marginal at best when compared to today's options. Wad cutters and semi-wad cutters were the popular choice of officers - as funny as that may sound to our ears today!

So, comparing a modern 9mm round that is tuned to pass the FBI spec of penetration and expansion to a 357 mag is going to show less of a difference. There is still a difference, but it is far less dramatic than in the past. Given the choice of identical weapons with only different calibers, the more powerful caliber will give the better performance. BUT... it may take many hundreds or thousands of shootings to verify the difference statistically. A clean miss with a .50BMG is less lethal than a COM hit with a .32 acp.

That's my take on it anyway.

jb
 
Think in terms of a formula like mass x velocity = impact energy.
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Momentum (mass x velocity) is NOT energy.

Using the correct terms and definitions really matters when discussing things that are directly related to energy and momentum.

Acceleration is a CHANGE in velocity.

A change in the quantity, or the direction of the velocity vector.

The change in direction is how centripetal force occurs.
Even if you swing something at a constant RPM, the change in the direction of the velocity vector creates centripetal force you feel as the object tries to fly off in a straight line.
 
Vel vs mass vs KE...

I'm sure another member may get in a bind over it but my point is that a fast moving bullet like a .357magnum, .357sig or .40S&W/10mm can get a lot of power & speed.
There may be valid reasons to carry/pick other rounds; 9x19mm, .38spl, .44spl, etc but that could based on recoil, muzzle flash, firearm etc.

I think there is a strong arguement for using a .40S&W or .357sig over a .38spl or .357magnum or a 10mm but that is based on multiple factors not just KE vel etc.
 
Just a question for the "beter than" crowd...

I tend to try and not think in terms like these...

"A COM hit with a .25 auto is better than a clean miss with a Hi-Tech, flechette, Metal-Storm, Incindiary God Bullet."

When speaking in terms of actual shootings and practical application, I wonder how those of you who tend to think this way (granted with a little less gusto) would react to a pointed question of supperiority as follows...

Which is better...
1. A com hit with a .22lr that impacts the dead center of the sternum (which is the target).
2. A hit with a hi-velocity .357 magnum round within a 4 inch radius of the privious impact.

At combat distances, these are the questions that you should ask yourself. One rarely carries a weapon that they do not train with (or shouldn't). I know I can connect with my carry weapon, though maybe not quite as accurately as with a low-recoil weapon like a .22lr. But if you're aiming COM, even giving a relative birth of room for error, a hi-velocity round still wins.

If you're still a skeptic, let's see if the other way sways the upper hand.

Which is better...
1. A com hit with a hi-velocity .357 magnum round that impacts the dead center of the sternum.
2. A hit with a 22lr round within a 4 inch radius of the privious impact.

Still a skeptic?
Take a COM hit out of the equation. What if you shoot wide and get a limb shot? Is a COM shot with a .22lr better than a leg shot with a .357 magnum? Which perpetrator has a greater chance of shooting back?

I don't think I'm being unreasonable by challenging this kind of logic, let's just be a little more logical about it.

~LT
 
Okay guys it seems my question was too complex.

Let me simplify it.

I am trying to decide if I should buy a .357 sig instead of a 9mm. That was the original question I wanted answered.

Now obviously the speer gold dot .357 sig is the best round out there for the sig. So I was comparing it to the 9mm gold dot +p offering.

Will I have anything to gain going to the .357 sig?

I am not concerned about price. Or is the recoil and the flash not really worth the extra velocity?
 
Dead simple answer. Your .357 sig has the potential to be a better disabler. It is faster, this gives higher momentum and higher KE,and those two things are what cause injury. As I have said, there are no guarantees, and you would have to plan for good bullet performance for either round. (whatever you call good bullet performance)

The bonded or solid copper bullet is a great thing at high velocity. It should be used.

I suspect that if you are trained on a 9mm or .40 with powerful loads, a .357 sig will present no serious obstacles to moving up in power. Of course it will be more intense. It is supposed to be. But, I believe that a serious shooter is able to get over the difference in recoil, and the difference in muzzle blast will be a non issue. Use better hearing protection, and hope that you never have to use it while stuck in a shower stall.
 
I wouldnt dismiss temporary cavities from pistol rounds. Even if it doesnt create permanent damage, its going to be shockingly painfull to have organs rapidly displace and reset from the temporary cavity. That might have some incapacitory value but more of the psychological sense than a physical sense. Its' going to hurt.
 
Re: Daryl's explanation

The laws of physic's dictate that two identical bullets of the same wieght, expanding at the same rate and to the same diameter, but at different velocities cannot have identical penetration in identical materials.

So something has to be different.

In this case, I'd suggest the rate of expansion is different if all eise except velocity is equal. IOW, the faster bullet will have to expand at a faster rate, and reach full expansion sooner than the slower bullet in order to penetrate the same depth.

The faster expanding bullet (the one with highest velocity) will cause more trauma to the target by reaching the same diameter earlier in it's penetration.
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I am with Daryl - he must have paid attention in physics class.

If the 2 similar bullets strike with different velocities, but stop in the same distance, then that means the faster bullet encountered greater drag, no question about that (because it decelerated faster). Since the final diameter also appears to be the same, then that implies that the faster bullet expanded at a higher rate, to reach the larger diameter (higher drag) profile earlier in it's traversal of the gelatin. That explanation is also consistent with many other observations of hollowpoint bullet expansion - the faster they strike, the more quickly the bullet opens up.
 
Super if you really want to find out how important velocity is, slowly walk into a brick wall, then back up 50 feet and run as fast as you can into the same wall.
 
final question

"Will I gain anything by going to the 357 SIG from the 9x19?"

Not if your 9x19 ammo takes a 124/125g JHP bullet to 1370fps.
 
"Dont rock the jutebox".....

In short, the .357sig is a much better selection for a number of reasons, not just power/vel.
To me, the common .357sig wt/size rounds are like a .357magnum for a semi auto pistol. ;)
It feeds/cycles great, is accurate and can be had in most major brands(Speer Gold-Dot, Corbon, Winchester, Federal, etc).
Some of the "keyboard commandos" & gun shop rangers may call the .357sig a wildcat or knock it but many large LE agencies issue the .357sig and it's saved LE officers lives in duty use.
 
Super if you really want to find out how important velocity is, slowly walk into a brick wall, then back up 50 feet and run as fast as you can into the same wall.
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And a great demonstration of the fact that greater velocity will result in greater tissue damage, all things being equal.
 
Super,

Your original post indicates that you were primarily looking at this from the point of view "which would be best for self defense" in the narrow sense of which is more powerful and thus more likely to stop an attack. Or at least that is how I read it. So...

Yep the .357 Sig is a more powerful round than the 9mm. "More powerful" because it's higher velocity provides the bullet with more energy with which to do it's work. Because of this it will and can provide a slight edge over the 9mm in stopping an attack.

You also mentioned the 40 S&W and the 10mm. Both of those are, or can be with the right load and bullet, more powerful rounds than the .357 Sig or the 9mm. In the case of both the 40 and the 10mm greater bullet weight and the slightly larger frontal area of the round play a role. These factors in bullet performance have not been mentioned much in this thread. But that is another discussion.

http://ammo.ar15.com/project/Self_Defense_Ammo_FAQ/index.htm

In looking at the two rounds, 9mm vs. .357 Sig a number of other factors can come into consideration. The guns, availability and price of practice/range ammo, availability and price of quality defensive ammo, magazine capacity, the way it shoots in your hands, etc. I assume you've already looked at these though.

tipoc
 
drooling logic

If we're just talking "rounds", then the 9x25 is the correct choice.



I really did think it was just the velocity of the bullet that mattered :confused:
 
Weshoot sez:

I really did think it was just the velocity of the bullet that mattered
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Some folk do, as you know :). Or at least some in the shooting/ammo/firearms industry try to convince folks of that. .357 Sig has been around since 1994 or so only the last couple of years have they figured out how to market it.

9x25 shoulda been more successful. A very good round. But it leads a good life with it's fans. :)

tipoc
 
Velocity, like size, always matters!

How much it matters depends on how much of each you have in relationship to what ever you are comparing it to.

IF trying to decide on a 9mm vs a .357 Sig, consider, you are comparing a +p+ 9mm load to the regular .357 Sig loading to get nearly the same performance. So, only the "best" 9mm comes close. And how much of your shooting will be with that "best" (and expensive) 9mm load?

Nothing living can tell the difference of 100-150fps velocity when shot. Real world performance does not consistantly duplicate the calculated advantage of 150fps, except for long range trajectory. There it matters a little, and the difference is real, measurable, and repeatable.

Performance inside a human body has too many variables to be able to accurately and consistantly predict. Differences in impact speed, angle, tissue density, bones, etc, etc, etc. On paper, the (slightly) faster round gives you an increased potential, but in reality, its not a given.

When you get enough of a velocity difference, real world results do show significant improvement, but even then, its not a linear model. A 40% increase in speed does not ensure a 40% increase in effectiveness. Significant correlation exists, but not at a one for one ratio.
 
the direct measureable result of a faster bullet would be the faster bullet will reach the target at any given distance first. its doubtfull you would be shooting at a target at a great enough distance that the speed difference would matter much in real world (example: dodging).

the real test is how the bullet transfers the force of the velocity into the force of impact. the faster bullet has the potential to impart a greater force, but there are many other factors other than velocity that dictate the sum of that equation.
 
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