Does speed matter?

Looking at some defensive ammo in the ammo safe this am. 357 sig vs .45 critical duty. Stated 1350 fps v. 990. Guessing in a defensive situation, 300 fps+- faster can be a life saver?

There is more to terminal ballistics than velocity. Ammo and Ballistics 6 gives the Taylor Knock Out Index as:
.357 SIG @ 1350 FPS as 8.6
.45 Critical Duty @ 975 FPS as 13.9

In the same reference the highest Taylor Knock Out Index for each caliber is:
.357 SIG Hornady 147 grain JHP/XTP Velocity 1225 Index 9.2
.45 ACP Federal 230 grain Guard Dog Velocity 1140 Index 16.9

Google Terminal ballistics and start reading. Here are a couple to get you started:

http://aegisacademy.com/terminal-ballistics-part-i/

This rapid incapacitation is a factor of shot placement combined with velocity, kinetic energy, projectile weight, projectile shape and construction, caliber, and range to target as well as the nature of the target itself.

Click to expand...

http://aegisacademy.com/terminal-ballistics-part-ii/

Accuracy of first shot matters above all else.

There's two major theories...the momentum theory vs. the velocity theory. Both have their adherents and both can be right or wrong depending on circumstances. Bullet technology has improved so much the differences in handgun ammunition may be all but moot anymore. You also have to factor in ball ammunition vs. hollow points vs. soft points. All have different properties and will perform different in the body...and not all bodies are made the same and it gets even more variable as you add other barriers such as thick vs. thin clothing, overcoats, frontal impact vs. side impact and whether bone is hit. The way I see it any hit is gonna hurt...placement can easily make the difference.

I've heard this described one way...not necessarily a scientific or factual way of looking at it..."Which do you think you would feel will hurt you the most...a golf ball at 1350 fps vs. a bowling ball at 990 fps?"

There's also the advice credited to Wyatt Earp...when asked he supposedly said "Speed is fine...accuracy is final." Also attributed to him when asked about the need for a fast draw "In a gunfight...take your time...quickly!"

accuracy and bullet selection always come first. but speed kills, kinetic energy on the target. the formula for energy is 1/2 mass times velocity squared, so velocity is a huge factor.

Velocity is just one inter related factor among a whole bunch , particularly in the OP's example of .357 Sig vs .45 acp . Different cross sectional area , sectional density, momentum , energy, etc .

Now if you made the comparison more of an Apples vs Apples , of say .380 acp vs 9x19 vs .357 sig all of similar bullet designs , then velocity per se becomes more indicative .

Momentum is basically the measure of how much tissue volume a bullet can crush, tends to favor heavier bullets, where energy can aid penetration of hard objects, increases the pressure on a bullet to expand, and can cause some tearing at high (2K+ FPS) velocities, which tends to favor lighter bullets. Energy doesn't matter as much as momentum in handguns, being the majority don't have the velocity do much with a stretch cavity, but it does come at a big expense in recoil, and muzzle blast. Good bullets in either caliber will penetrate sufficiently, each has it's benefits / problems, so for the most part it comes down to what you can shoot faster/better. IMO most underestimate how much muzzle blast can rattle you when shooting in low light without ears, I opt for heavy bullets at lower pressures, std 124-147gr 9mm, 180gr 40 and std 200+gr 45 tend to be much easier to deal with than 357 sig, or light, hot +p 9 and 45. That, along with capacity and aptitude with that particular pistol would be a bigger consideration than the relatively small differences in terminal ballistics.

Zorros said:

Looking at some defensive ammo in the ammo safe this am. 357 sig vs .45 critical duty. Stated 1350 fps v. 990. Guessing in a defensive situation, 300 fps+- faster can be a life saver?

Click to expand...

What is a life saver, is really being aware of your surroundings, practice, and training. If someone gets the drop on you there is nothing that will get you out of the predicament. As I told my son, it doesn't matter if you have the latest, slickest firearm and the other guy has order single action army. If you miss, your are toast. If you don't know went, were and how to your firearm it can be just as bad. These type of choices are really just personal choice. I'm not talking about taking a pistol to down a water buffalo either.

Too much velocity with the wrong bullet can also cause less penetration due to early expansion. It also increases the risk of core jacket separation. I just left the firearms manufacturing industry after 6 years. Many ammo manufacturers are constantly trying to come up with ideas they can sell as the latest and greatest wonder, in a product field where the technology has already been nearly maxed out for literally decades. Most of it's nothing more than ********, IMHO.

Ok , I Just double checked the Critical Duty offerings . There are two .45acp loads, and one .357 Sig .

Short version - Any of the three would be a very good choice .

Long version - Make your choices based upon the ancillary details . What flavor of pistol ? Bbl length ? Your abilities and comfort level of dealing with recoil ? Does the environment or your skills make long range trajectory a meaningful factor ?

I've always been a fan of bigger is better when it comes to handgun ammunition (within reason)...but bullet technology is better than it used to be. While I will always be a .45 ACP aficionado I have become a huge proponent of the 10mm though I believe it's possibly too potent for many if not most people to use as effectively as a .45. I've also come into a supply recently of 9mm +P+ which be the hot ticket but I haven't had the opportunity to try it out yet.

Boy , I'm feeling old now . I was first a fan of 9mm +P+ 30 plus yr ago .

Back in the day I was equally comfortable with .45acp or hot 9 ( so far as bottom feeder ctgs ) . When .40 came out was unimpressed , saw it as half a$$ compromise to fill a mostly non- existent gap . ( But ultimately it ended up outperforming initial expectations .)

Blacksmith101 said:

<snip>
Google Terminal ballistics and start reading. Here are a couple to get you started:

http://aegisacademy.com/terminal-ballistics-part-i/


http://aegisacademy.com/terminal-ballistics-part-ii/

Click to expand...

Good reading - seems pretty solid on the quantitative part, and as far as this non-combat, non-LEO type can tell, makes good sense overall.

Hope this thread keeps going, I could learn a bit here...

Beating the drum for 9mm because it's easy to shoot with low recoil, then loading +p+ ammunition does not compute.

Speed matters. I think the question you are asking is; how much does it matter.

Nothing matters if you don't hit your target. You will be held responsible for what you hit when you missed. So my first rule is have a gun and second, know how to use it properly. In other words, carry what you know you can shoot accurately. IMO, much of accuracy comes from practice so shooting something that you can afford to shoot a lot of is pretty important. No surprise here but more people have been killed by .22lr than any other caliber. It is a preferred caliber among people that do very close wet work. Accuracy at two feet distance on an unsuspecting target by a practiced killer takes caliber choice way down on the priority list.

Much of the importance of firearms for self defense is psychological. Many people who pull a gun in defense never have to pull the trigger. Caliber is unimportant in these situations. A pellet gun that deters a criminal without being fired is every bit as effective as a .45 ACP. Of course bluffing without having anything to back up your bluff is dangerous enough in poker so I would never recommend it as a strategy for defending your life or those of your loved ones. If you are one of the many people who carry different handguns on different occasions, I am going to suggest that if, on the very bad day, you are forced to pull your handgun, the last thought that will never occur to you will be; Which caliber handgun am I carrying today? You have what you brought so bring what you have confidence in. Know that when you have to pull the trigger that the bullet will go where you send it and leave the rest to God. Because, bullets do funny things once they begin changing mediums, like from air to clothing, to flesh, to bone, to concrete, to wood, to glass, etc... Guessing the final trajectory of any bullet after it leaves the gun is a job for Super Physicist; able to calculate large numbers without the leap of a calculator.

A simpler physics problem would be: If you were standing on a train track and you had the choice of being shot by a very fast but small bullet OR struck by a large and heavy freight train rolling at a mere .5 miles per hour...I think you can see where I am going with this. The correct answer is get off the damn track before either object hits you.

Good luck finding what works for you. Buy lots and shoot often.

Be safe.

I already shot full power 125jhp from .357 Mag , I wanted as close to that as I could get in a G17 .

Zorros said:

Looking at some defensive ammo in the ammo safe this am. 357 sig vs .45 critical duty. Stated 1350 fps v. 990. Guessing in a defensive situation, 300 fps+- faster can be a life saver?

Click to expand...

I'm gunna pick two good loads for each cartridge and go from there. I'm using the data from luckygunner to be consistent...although they use a 3.6" barrel for the 45 and 4.5" barrel for the .357 sig(meaning the 45 is at a slight disadvantage in terms of velocity due to the difference in barrel length).

45 acp- 230gr ranger t

Velocity- 900
energy- 413
momentum- 29
penetration depth- 14.5"
expanded diameter- 1.00"
wound volume- 11.5 in^3

357 sig- 125 gr PDX1

Velocity- 1423
energy- 561
momentum- 25
penetration depth- 15.4"
expanded diameter- .69"
wound volume- 5.3 in^3

This data is strictly comparative performance of ballistics gel, but it's close enough to make some observations....especially if you recognize that a handgun projectile will basically only cause wounding through the tissue the front of the bullet crushes. You'll notice the .357 sig has both greater velocity and energy, but the .45 crushed almost twice as much tissue...so how?

Energy is the work something can do. In terminal ballistics, the work being done is the crushing of tissue, deforming of the bullet, and temporary displacement of tissue. So basically, the .357 transfers energy more into the displacement of tissue as it is radially projected outward, while the .45 transfers more energy into crushing the tissue in front of it. The .45 has greater momentum and will also deflect less after striking something(like bone or windshield). However, fast= penetration of hard barriers, so .357 sig may do okay at penetrating something like the skull.

In an actual use of force, the above stuff is only part of what is going on. If you used something like the 230 gr hst load at 822 ft/sec, 14" penetration, and .85" expansion... you're now much closer, at 5.74 in^3. So, if you don't use the optimal load for each and change one or the other, it has a huge(relative) impact on the terminal ballistics results.

If you fire either out of a subcompact vs. full-sized gun, it will also change the results. Bullets are designed to operate in a velocity window. If you speed up the bullet, it expands more but penetrates less. If you slow it down, it penetrates more and expands less.

Outside of the terminal ballistics, you've also got the shootability factors. How fast can you dump a mag into a target at a given range? If you can dump a mag of 9mm into a target faster than you can dump a mag of .45 into a target, the 9mm may give you the ability to cause more trauma where you want it, faster.

This is important because shot placement is more important than just about anything else in terms of stopping a threat. To stop a person from attacking you, you can a) make them choose to stop b) force their body to stop. Some people choose to stop when they see a gun, some choose after being shot...but some never choose to stop and must be physiologically stopped.....sooo....b, how's that work?

To physiologically stop someone you can: 1) Shut off the signal to their body with a CNS hit 2) Make them pass out from blood loss 3) cause enough damage to a body structure to keep them from using that structure against you. Of these choices, the CNS shot is the clear winner.....except that the CNS is small....wrapped in bone...and at the back of someone's body(spine). If you can hit it...awesome...but chances are you won't.

Option 2 takes time. The quicker you can make blood leave someone's body, the quicker you can get them hypovolemic and passing out. Large holes are good and multiple holes are better...as long as they're through important structures that bleed a lot. Again, shot placement is critical. The difference between a hole in someone's Bicep(but missing major arteries) and a hole in the heart is much greater than the difference between a 9mm vs 45 in either location.

Damaging structures of the body is meh. If you've ever seen a deer get hit by a car and then run away, you can think how someone could still continue an attack on you, even with a shattered hip.

So... all this is a more long-winded way of saying blaster's right.

I heard that if you shoot someone in MD with a "designer" round and they die, the States attorney will argue that they might have survived if it weren't for the KILLER bullets you used.

This is just what I heard.

When I had my .357 magnum for home defense, I just loaded it with standard Federal hollow point 38's under the assumption that there would be a better opportunity for a good follow up shot, especially if my wife was pulling the trigger. Less bang and muzzle flash when your stressed and half asleep is a plus to be considered along with ballistics.

Also, it's my understanding that speed REALLY starts to matter at about 2900 fps where it creates a huge shock wave that turns muscle into jello. Below that, the extra speed does more damage/has more penetration, but not exponential damage lie you get when you break that 2900-3000 fps threshold.

And how much penetration do you need in a home defense situation?

Amigo109 said:

Also, it's my understanding that speed REALLY starts to matter at about 2900 fps where it creates a huge shock wave that turns muscle into jello. Below that, the extra speed does more damage/has more penetration, but not exponential damage lie you get when you break that 2900-3000 fps threshold.

And how much penetration do you need in a home defense situation?

Click to expand...

I think the 2900-3000 threshold sounds more like the velocity needed for 5.56 fmj to fragment reliably as it tumbles. Depending on the exact load, generally 2,000 fps is where tissue stretches enough from the temporary cavitation to start tearing(especially if fragments are in the cavity to act on the tissue under tension). This changes, depending on the tissue though. Something like the liver or brain will be more prone to tearing and being damaged from its radial projection than something like muscle.

Let me re pose the question ( althought a great discussion followed the original question). Any anecdotal evidence Of a negligible, but life saving, benefit to getting your bullet to target 300+ ft faster than the opponent? Say, if you are .5 second faster to shoot. .25 faster to shoot?