Compare 9mm, 40 S&W and 45 ACP in Self-Defense Shooting?

[jackstrawIII]

My GUESS is that it might be due to something I can't quantify that I'll call "dwell time" and involves momentum/inertia, not just pure ft/lbs of energy.

Bullets don't penetrate the steel, nor do they fall to the ground in front of it, so clearly not every bit of their energy is transferred to the popper.

So, I think its a matter of how much (%) is transferred DURING the time the bullet is in contact, "pushing" on the popper.

Might it not be that the larger, heavier, SLOWER moving bullets "push" LONGER even though on paper the energy level is the same???

Think of a safe door. SLAP the door, and it barely moves. PUSH the door, with a force equal to the slap, but over a longer period of time, and the door moves.

Might it be just that simple???

Yup. Momentum and force applied over time.

This is the same reason you don't try shoulder shots when hunting with a lightweight bullet. It has energy, but gets its energy from velocity instead of mass and so it applies that energy differently when it contacts the target.

Use what works... incidentally, when shooting living creatures, most bullets seem to work ok.

 

[ShootistPRS]

This is why HP bullets have had a big following in the metallic silhouette games. The bullet spends more time in contact with the target before the energy disintegrates it. It is also why equal weights of slug and shot from a shotgun leans to the shot being more effective. The amount of momentum is important but the time it is applied to the target is even more important.

 

[OldMarksman]

Might it not be that the larger, heavier, SLOWER moving bullets "push" LONGER even though on paper the energy level is the same???

No. The elastic collision is instantaneous, regardless of the masses of the colliding objects. Nothing "pushes" anything "longer".

Think of a safe door. SLAP the door, and it barely moves. PUSH the door, with a force equal to the slap, but over a longer period of time, and the door moves.

A bullet's velocity changes in magnitude and direction immediately upon impact. The sum of the momenta (mass times velocity) of the bullet plus the door remains unchanged after the impact--thus, the door gains velocity.

If that "slap" imparts the same impulse to the door, the result will be the same.

When one continues to "push" the door, the relevant factor in the elastic collision becomes force times distance, which is work, or kinetic anergy.

Might it be just that simple???

No.

 

[OldMarksman]

The amount of momentum is important but the time it is applied to the target is even more important.

If the projectile were to stick to the target, one might conclude that the "time" that the momentum is "applied to the target" would be essentially limitless.

But it would not be. After the projectile stops, or more accurately, after the projectile changes velocity, momentum is no longer being applied to the target.

It may seem counter intuitive, but an arrow that bounces off a target will impart more momentum to the target than one that sticks to it.

 

[mavracer]

If that "slap" imparts the same impulse to the door, the result will be the same.

The results will never be the same when you slap the door your hand represents less mass than it does when you push the door, so in order to move the door the same amount the momentum must be equal and your slap will have higher kinetic energy the added energy will not present itself as door movement it will present itself as a loud noise and a burning sensation in your hand.

 

[OldMarksman]

If that "slap" imparts the same impulse to the door, the result will be the same.

The results will never be the same when you slap the door your hand represents less mass than it does when you push the door, so in order to move the door the same amount the momentum must be equal and your slap will have higher kinetic energy the added energy will not present itself as door movement it will present itself as a loud noise and a burning sensation in your hand.

I would not assume that the momentum imparted by a slap is limited to the velocity of the hand times the mass of only the hand. It depends upon how the strike is administered.

One who slaps, punches, or otherwise strikes something may be doing so by moving much more mass than that of only the face of the hand or of the palm of the hand or of the fist.

I did say that momentum--the impulse--would be equal. If it is, it will result in the same door movement.

BUT--the analogy of striking someone with a body part is not really a very good one, and it only applies in the abstract. That's because in reality, when one pushes on a door, or on a hinged steel target, with the body--any part of the body--the transfer of energy and momentum continues after the instant of contact. That's because the muscles continue to exert force.

Not so with a bullet. All of the energy and all of the momentum that a bullet has available to impart to another object was imparted to it at the instant of firing. There will be no more. That differs from pushing on a safe door with bodily force. The the analogy is really not a very good one.

But if we were to throw something at the door of the safe, we would find that the movement of the door would be proportional to the momentum of the thrown item--the mass times the velocity--before the collision, regardless of what it was that was thrown.

Kinetic energy would be conserved only in an elastic collision--one in which neither object is deformed.

 

[walks with gun]

Many of us carry a handgun for different reasons, I live out in the boondocks and am probably more likely to run into feral dogs, coyotes cougar, wolves or black bear than a criminal or terrorist. My favorite carry gun is usually a 1911 in 45acp loaded with 230gr. cast trunce cones travelling about 850fps. I have a lot more faith in this than any 9mm load. I know it's not a very scientific test, but I shoot a lot of steel targets at various ranges and when shot with the 9mm's they ting when hit, when hit with the 45's, they really thunk and swing. Also when shooting blocks of wood, the 9's will move them around and often knock them over, but when shot with the heavier 45's they tend to fall more often and get blown back further. There must be something to this. It would be pretty darn hard to convince me the 9mm is as good of stopper as the 45, and I feel the 40S&W is right up there with the .45acp..

 

[OldMarksman]

I know it's not a very scientific test, but I shoot a lot of steel targets at various ranges and when shot with the 9mm's they ting when hit, when hit with the 45's, they really thunk and swing. Also when shooting blocks of wood, the 9's will move them around and often knock them over, but when shot with the heavier 45's they tend to fall more often and get blown back further.

No, it is not scientific, but more importantly, it is not relevant.

There must be something to this.

There is, but it has nothing to do with stopping effectiveness.

 

[walks with gun]

I will disagree, it's all about weight and bullet surface. As the OP said, the larger calibers knock down poppers better than the 9mm, it's because their BIGGER.

 

[mavracer]

I would not assume that the momentum imparted by a slap is limited to the velocity of the hand times the mass of only the hand.

I didn't, I only said it would be effectively less mass, because if we're honest with the analogy(heavierXslower=lighterXfaster) it has to be.

No. The elastic collision is instantaneous, regardless of the masses of the colliding objects. Nothing "pushes" anything "longer".

No true nothing of mass can move instantaneously, besides a bullet hitting a popper isn't by definition a elastic collision as the bullet is in fact deformed.

 

[OldMarksman]

I will disagree, it's all about weight and bullet surface. As the OP said, the larger calibers knock down poppers better than the 9mm, it's because their BIGGER.

You may choose to disagree, but if you do, you are wrong.

It's basic physics. From Newton's Third Law we derive the law of momentum conservation. For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision.

The momentum of each object is the product of its mass and its velocity. A velocity vector has both magnitude and direction.

 

[OldMarksman]

...a bullet hitting a popper isn't by definition a elastic collision as the bullet is in fact deformed.

Touche!

But momentum is conserved....

 

[K_Mac]

This thread is as entertaining as the countless ones before it. I find it interesting comparing the performance of a 9 mm or .45 on poppers, and using that information to predict their effectiveness on humans.

There's a mountain of evidence showing that the difference in service calibers using quality self-defense ammunition on humans is very small. Being able to put rounds quickly on target is far more important than caliber. In light of this, shooting a service caliber in the weapon that one shoots best , i.e., quickly and accurately gives one the best chance of winning a gun fight. For a high percentage of us that is best done with a 9 mm.

Yes, a .45 has a nicer ring on steel than 9 mm. It also bangs solid targets around with greater authority. Using that to extrapolate that a .45 is a better self-defense​ choice for you or me is a mistake.

 

[walks with gun]

So your saying six fast punches of a 60lb. person will put you down faster than two punches of a 250lb. man. If weight and size have nothing to do with it, when dangerous game hunters go into the brush after a wounded animal, why are big bore rifles and shotguns more desireable than say a .223 bolt action. If fast hit's count, why do we all not carry .22lrs. Mathematical equations, only go so far in real world fight stopping.

 

[45_auto]

If fast hit's count, why do we all not carry .22lrs. Mathematical equations, only go so far in real world fight stopping.

If weight and size really matters, why do we all not carry single shot 12 guage pistols that shoot 500 grain slugs? Math works if you use it correctly in real world fight stopping.

 

[walks with gun]

Is a single shot 9mm, just as effective as a single shot 45.

 

[45_auto]

Yep.

You got anything that proves that it's not? It would be nice to see the longest running debate on the internet finally settled!

“Most of what is ‘common knowledge’ with ammunition and its effects on the human target are rooted in myth and folklore. … Handgun stopping power is simply a myth,” the FBI said in its report. “There is little to no noticeable difference in the wound tracks between premium line law Auto enforcement projectiles from 9mm Luger through the .45 Auto.”

 

[OldMarksman]

So your saying six fast punches of a 60lb. person will put you down faster than two punches of a 250lb. man.

Does punching power relate directly to mass? No, no one has made any such assertion.

If weight and size have nothing to do with it, when dangerous game hunters go into the brush after a wounded animal, why are big bore rifles and shotguns more desireable than say a .223 bolt action.

Stopping a dangerous animal requires much more penetration than stopping a human attacker.

If fast hit's count, why do we all not carry .22lrs.

Not enough penetration.

Mathematical equations, only go so far in real world fight stopping.

No one I know bases any conclusions on mathematical equations.

The key variables are penetration and rapidity of controlled fire.

For assessing penetration, people evaluate performance in surrogate media. It has been determined by the experts that premium grade 9mm loads are adequate for self defense.

Rapidity of controlled fire is important only insofar as it increases the probability of achieving proper placement timely.

One of the things that enable more rapid controlled fire is reduced recoil.

 

[walks with gun]

Since the invention of firearms, military and big game weapons have always been large bore weapons, the smaller stuff just didn't cut it when defending yourselves. Small caliber guns came about for the ease of carrying, not because they were more powerful, they were also easier for frailer people too handle. But as far as shot for shot, I believe that the bigger calibers are more effective.

 

[ShootistPRS]

A bullet from a pistol has very little momentum compared to a 200 pound man walking at 6 fps. A 12 ga. shotgun with a 1-1/4 once load at 1400 fps has enough momentum to stop a 200 pound man walking at 6 fps. Stopping the advance can give you time for another shot but it doesn't necessarily kill instantly. On the other side is that more often than not an attacker will lose enthusiasm for a confrontation when confronted with a gun. I never plan on that happening but it is very often the case. Even multiple attackers rarely press ahead when confronted with a gun.

There has been a big part of the equation missing in this exchange. The more aware of your surroundings the better your chance to be prepared. Looking someone in the eye and greeting them can often disarm a situation before it starts. I would not rely on that but most crooks want an easy target. I know that you can't always have your head on a swivel or be constantly aware of everyone approaching or departing from your space. What you can do is not allow yourself to go into tunnel vision when the woman in a tight sweater or short skirt approaches. Just keep your eyes, ears and gut feelings open to the area around you. If a 89 year old woman can stand up to three twenty-something thugs using her wits and a shotgun then most of us can too - if we are prepared. (she never fired a shot and turned all three over to LEO after preaching a bit about Jesus while they waited.)