Not a caliber war... Kinetic energy higher in 40 S&W

[icenoir]

Can anyone explain why the kinetic energy on 40.s&w tends to have more kinetic energy then a comparable 45?
This is most notable in gold dot:

9mm 124gr: 368
40s&w 165:. 484
45 ACP 230:. 404
45 ACP 200; 518 <added>

Hst
9mm 124:. 396
40 S&w 165: 468
45 ACP 230: 460

Winchester defender:
9mm 124: 396
40 S&w 165:. 476
45acp 230: 432

Thanks...

[TunnelRat]

Because for kinetic energy velocity is squared. This means changes in velocity equate to larger difference than changes in mass.
KE = m*v^2

Velocity is higher on 40SW, usually, and this is more impactful in the above equation than the standard differences in mass between 40SW and 45ACP.


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[jr24]

Especially with those 165 grain loads which have a higher velocity than the, I think, more common 180 grain loads.

[TunnelRat]

^ A good point. When you load a smaller projectile in the same cartridge you usually can achieve a higher velocity.


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[CDW4ME]

IME "caliber war" is a nonsensical term invoked when one doesn't like a caliber discussion.
Anyway, if KE is of interest, 357 Sig Gold Dot generates 500# KE from a 4'' barrel. (125 gr @ ~1,350 fps)


In before KE doesn't matter comments.

[tangolima]

Originally Posted by TunnelRat

Because for kinetic energy velocity is squared. This means changes in velocity equate to larger difference than changes in mass.
KE = m*v^2

Velocity is higher on 40SW, usually, and this is more impactful in the above equation than the standard differences in mass between 40SW and 45ACP.


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KE=1/2*m*v^2

.45 ACP max pressure is 21k psi. .40 s&w has 35k psi. That gives a clue. Basically .40 s&w gets to go much faster with only slightly lighter bullet.

.40 s&w has up to 500 ft-lb energy. It can lift a 200 lb guy 2.5 ft off ground. Wait. Why doesn't the shooter fly off the ground? Newton's 2nd rule doesn't work anymore? Hmm..

Anyway, another useless factoid. Increase bullet weight usually requires lower charge to avoid exceeding max. pressure (gun blowing up). The muzzle velocity will be lower too. However the kinetic energy is usually higher. Less powder, higher energy, higher efficiency. What's going on? Why do we want to burn more powder to have less energy?

-TL

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[TunnelRat]

Originally Posted by tangolima

KE=1/2*m*v^2

Thank you. In my defense I’m home sick, but still that’s embarrassing.


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[jmr40]

As others have stated bullet velocity is far more important than weight when it comes to calculating energy.

I'm not saying that using energy numbers are useless in predicting bullet performance, but they can easily be misunderstood. Sometimes when comparing 2 different cartridges the one with the most energy is the most effective, but often that isn't the case. There are other, more important factors to consider.

For example, the trend at one time was to shoot very light 185 gr bullets in 45ACP to get velocity and energy numbers elevated. That looked good on paper, but those bullets were very short in relation to diameter. Plus, at the speed they impacted they expanded violently. Those factors resulted in poor penetration.

A 180 gr bullet fired from a 40 S&W at about the same speed is much longer in relation to diameter and results in better penetration.

[wild cat mccane]

Gold Dot is measured with a 4" barrel in 9mm.

It is measured with a 5" barrel in 40 and 45.



http://www.le.vistaoutdoor.com/ammun...C53999%2C54256

[Jim Watson]

Although the .40 was introduced with a 180 gr bullet to approximate the FBI light 10mm or a 185 gr .45, the Jello Junkies, the Morgue Monsters, and the Police Blotter evaluators all concluded that a lighter, faster bullet was more effective.

The .357 Sig is said to have been meant to equal 125 gr 4 inch .357 Magnum; well, a 155 gr .40 is very close to a 158 gr 4 inch .357 Magnum.

[44 AMP]

As already mentioned, the reason for the higher KE number due to speed, having a greater role in the equation we use to calculate the amount of energy. That's all.

For example, the trend at one time was to shoot very light 185 gr bullets in 45ACP to get velocity and energy numbers elevated. That looked good on paper, but those bullets were very short in relation to diameter. Plus, at the speed they impacted they expanded violently. Those factors resulted in poor penetration.

A 180 gr bullet fired from a 40 S&W at about the same speed is much longer in relation to diameter and results in better penetration.

While this accurately describes the results, the reasoning is incorrect. It is not the length of the bullet that is the prime factor in penetration, it is the width. And MASS and SPEED, all combined.

Length results from the restriction of bore size on the mass of the projectile. Given equal mass (weight) and using the same material, the smaller diameter bullet MUST be longer. There is no getting around that. Length is the result of given weight and bore size.

It is not the length that determines how well something penetrates, it is the width, specifically the size and shape. Pointed things poke better than blunt ones. Narrow things poke better than fat ones. When the available force is the same the smaller diameter object will penetrate easier, resulting in deeper penetration.

As a simple example of the principle, say you step on a nail, the force of your foot coming down is the constant. Same amount of KE. Step on the point of the nail, it punctures your shoe and likely your foot. Step on the head of the nail (much wider compared to the point) and it usually doesn't puncture your shoe. Length of the nail doesn't matter. Width of the contact area, does.

Those 185gr .45 bullets that were driven fast and expanded too much and didn't penetrate well didn't underpenetrate because they were short, they under penetrated because bullet construction was inadequate for the impact speed, and they expanded too much (making them WIDER) and more of the available energy was needed to push them through, so they didn't go as deep.


Now, on to KE. Some folks will probably put me in the group that says KE doesn't matter, but I say the number you get on paper using the standard formula doesn't matter the way most people seem to think it does.

First, as you've seen, the math is heavily slanted to give velocity the most "weight" in the formula.

Second, the amount of energy needed to do a specific job is what ever it takes to get the bullet where it needs to go to do the job it needs to do. And THAT will vary considerably. More than needed is rarely a problem, less than enough can be a very serious problem. Since we can't know how much will be enough we strongly tend to use as much as we can.

And that is what the calculated KE numbers are for. For a relatively fair comparison between the very different calibers, and speeds, based on a common standard. If round A calculates to 700 and round B to 450, that shows clearly A is significantly more than B, on paper.

This does NOT translate DIRECTLY to performance in the field. There is a relationship, but it is not mathematically linear or constant like a formula. There is no "dead+" or "stopped ++",

Once the KE level is above the minimum needed to physically perform the task, the paper KE number is not relevant, it is other factors in combination that determine how well the shot "works".

Another example, (using rifle rounds to illustrate the extreme difference possible)

You can load a .22-250 and a .45-70 to an IDENTICAL amount of KE. EXACTLY the same amount of KE using the standard formula. Very small bullet, moving very, very fast, vs. very large bullet moving much, much slower, giving exactly the same results using the KE formula. SO, based on KE alone, they should be the same in the field, right?

They aren't. And that's because KE isn't alone. It's only one factor among many, and those other factors have a more dominant effect in the real world performance than KE alone does.

.22-250 vs. .45-70 with equal amount of KE in both. Which one of those would you pick to stop an angry large animal?? On paper using KE alone, there should be no difference, but in the real world there is a huge difference and that is because of factors other than the calculated KE number.

I know which one I'd pick, by choice, and its not the .22 caliber one.

[tangolima]

Energy is not everything. Without energy you have nothing.

-TL

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[totaldla]

My 40SW 155gr loads run 1350fps over my chronograph - 627ft/lbs.
You can't get there with the mighty 9mm.

[wild cat mccane]

Nope.

Nor do you or I net any benefit from that FPS using HST or Gold Dot that have built in expansion limits while being better hollow points than any other.

I bet a random 380 FMJ goes deeper than that load too because you speed is so high.

[TruthTellers]

Originally Posted by wild cat mccane

Nope.

Nor do you or I net any benefit from that FPS using HST or Gold Dot that have built in expansion limits while being better hollow points than any other.

I bet a random 380 FMJ goes deeper than that load too because you speed is so high.

Any .380 FMJ would go deeper than any 9/40/45 JHP, so what's your point? That the .40 going that fast will have inadequate penetration with a hollow point?

The only benefit I can surmise to the higher velocity (and thus energy) is it extends the effective range to the target to where a hollow point will expand. In a world where self defense takes place measured in feet and not yards, it makes no difference. For police and possibly military where they could be required to shoot at people many yards away, it could be vital to have a bullet that won't overpenetrate and be a danger to others.

[totaldla]

Overpenetration is a myth. Look up Buffalo Bore 155jhp penetration in ballistic gel. I think you guys need to get out more.

[44 AMP]

Overpenetration is a myth.

No, sorry, overpenetration is a fact, not a myth.

However it is not a fixed point, and is entirely subjective. One man's adequate penetration is another man's overpenetration. Complete penetration becomes overpenetration IF you do not want the bullet to do that. If you do want the bullet to completely penetrate, then its never overpentration, its adequate or sufficient penetration.

Personally, I WANT complete penetration. But, I'm not a big city police department. In any defensive shooting situation, my only priority would be saving my ass (by stopping the attack) not saving my dept's budget.

I feel two holes are better than one, when it comes to stopping a living thing. A round that completely penetrates demonstrates it has the ability to get where it needs to go, and if it misses a vital spot, that's on the shooter, not the bullet or the load.

[totaldla]

Originally Posted by 44 AMP

No, sorry, overpenetration is a fact, not a myth.

However it is not a fixed point, and is entirely subjective. One man's adequate penetration is another man's overpenetration.

What??

Guys get all excited because the all-knowing FBI decided that bullets should not penetrate further than 18". So if you're in the Cop business, you've probably got to pay attention to the FBI.
I'm not in the Cop business. Overpenetration having legal ramifications to those not in the Cop business is a myth.
.

[wild cat mccane]

None of the current "good" ammo does go past 18". Before you HAD to launch a light bullet super fast to get it to expand. No more thanks to internal skiving and better bonding softer lead (ex HST vs PUNCH).

Even Critical Duty by Hornady isn't all that hot.

PDX1 is 1,000 fps.

But neither is the better bullet/round from Federal, HST. The really slow 150gr HST 9mm is nothing short of magic at less than 900fps, right up there with HST 147gr +P without the +P. 147gr +P is not matched for penetration and full expansion.

Vista publishes standardized testing for LE like the website I posted earlier about G2 9mm being an 1" shorter than .40 test. They have done for a while (older: https://le.vistaoutdoor.com/download...sertPoster.pdf), you'll see FPS isn't everything.

A 10mm FMJ, 9mm, 45, .40, and a .380 FMJ can end up going the same depth in gel. Resistance is an interesting thing.

So if we are talking just hollow points? Extra FPS isn't doing what you think either with a modern bullet. Underwood HOT ammo can end up going less deep because it expands faster (drag). HST/Gold Dot have built in expansion limits. Hornady XTP even more so. So...what you get from extra FPS needs to actually be defended, not factory slow FPS.

Thrust can't be the only of the four forces talked about...but it's the easiest to understand in our human minds.

[44 AMP]

Overpenetration having legal ramifications to those not in the Cop business is a myth.

I'd say that very much depends on where the bullet goes and what it does after it exits your target.

[Gas Bag]

I don’t know much except mass x velocity, and any pistol round that can reach 500 foot pounds, with a good HP, is OK with me.

I learned some time ago that speed kills, so I like good a speedy HP.

[Doc Intrepid]

Originally Posted by 44 AMP

"I'd say that very much depends on where the bullet goes and what it does after it exits your target."

+1

Such as when you're an arrogant movie star and your round goes through the slender female Cinematographer and then hits the Director standing behind her.

[wild cat mccane]

Yeah. Almost proved weapons can be dangerous huh?

[Lima Oscar 7]

I was drug into 9mmdom kicking and screaming. I like it. I trust it. I also like the .40 S&W (Sorry Gaston but S&W deserves credit so it’s not .40 Caliber). I was an early adopter of the .40 in 1993.

I am on the backside of my fifth decade. Things don’t mean as much to me so I have paired down my firearms inventory. One of my sons has my Glock Gen. 3 23 and my Glock Gen. 4 22. But…..I still have my Glock Gen. 5 27.

I won’t speak to ballistics. I’d say your covered well with a 9mm or .40 S&W but there is something about the 27. They carry well and are versatile. If my business has me in a capacity restricted state, I have the standard 9-Rd factory mags in tow. If I am in my State, I keep a 15 round reload in the left front pocket and I am all set.

The 27 Gen. 5 is the first actual .40 S&W pistol Glock has offered versus the modified 9mm platforms of the Gen. 2, Gen. 3 and Gen. 4. It’s surprisingly easy to shoot with 180 grain fodder. To me, my Gen. 4 Glock 21 is harder to shoot accurately than the 27 and it has an excellent trigger and finish if that’s important too you.