Ballistic Questions: Why exactly is a rifle more effective than a handgun?

With a longer barrel, rifles can develop higher velocities at lower pressures relative to a handgun, which requires more pressure (faster burning powder) to develop high velocities in a short barrel. Rifle rounds such as the .223 have a higher sectional density than handgun rounds and will penetrate more deeply, and in this particular example .223 has a tendency to yaw after hitting a target. Heavier bullets in the more powerful .308 have more mass and retain more of their velocity over longer distances and through light cover, obstructions, a tough target, etc.

In a vacuum a 9mm and a 5.56 round fired at the same time would hit the ground at the same time, a distance apart. In reality air resistance takes over and the 9mm would likely hit the ground first due to the higher ballistic coefficient of the 5.56 round (it more readily overcomes air resistance).

My lack of in-depth knowledge of terminal ballistics prevents me from elaborating much further.

Well most of it has to do with kinetic energy. Rifle rounds have more powder and barrel length to burn that powder in, making muzzle velocity higher. As a general rule of thumb, more energy means more tissue damage. Same reason why the .308 is more effective, having more kinetic energy than the .223.

To answer your question simply: Because the laws of physics say so

I will elaborate more when I'm back to a computer and not replying on my phone

Why is the rifle projectile more effective on a human target? What about a .308, why would that be more effective? I understand rifle rounds travel faster, but what does that mean to the target?

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Typically, a rifle round is more effective because it travels much faster than a handgun bullet. Bullets usually have two ways of wounding tissue (1) crushing the tissue immediately in the bullet path (permanent cavity) and (2) stretching/tearing tissue adjacent to the bullet path (temporary cavity).

To give an example, think of a milk jug filled with water. When you shoot it with a pistol, it will make a hold in one side of the jug and out the other side. Shoot the same jug with a rifle and it will explode the jug as the pressure wave in the water stretches the jug past its elastic limits. People are a lot more elastic than milk jugs, so the actual effect isn't quite so dramatic; but it uses the same principle.

Why are some rifle rounds considered adequate for varmints, some for large game, and some for dangerous game? What makes the (more powerful?) rounds more effective?

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Penetration mostly. If you shoot a small animal like a squirrel with a .223 that expands very quickly, it will explode similar to that milk jug. If you shoot a 300lb hog with the same round, it won't be very effective because the round will use up most of its energy before it reaches the vital organs of the hog. In order to be effective, a round has to be able to reach the vital organs or central nervous system of its target. Once it has sufficient penetration to reach those targets, the size of the hole it makes becomes relevant.

Likewise, if you shoot a hog with a big, slow-moving pistol bullet that penetrates its heart and both lungs, you can kill the hog right there. If you shoot a squirrel with the same bullet and it misses the vital organs and central nervous system, the squirrel will run off.

Another question: do all bullets fall at the same speed?

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Is this only because the 5.56 round travels farther in the time it takes for the earth to pull it into the ground? If the rounds are fired at the same exact time, will the bullets hit the earth at the same moment (but hundreds of yards apart)?

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This is fairly close on a basic level; but you are missing the effect of bullet shape on the equation. The 5.56 goes further because it starts out faster; but it also loses speed/energy much more slowly than the 9mm due to its more efficient shape. They won't hit the ground at the same time because the 9mm not only starts slower, it will slow down faster due to air resistance too.

Caveat: My grasp of physics is pretty basic compared to many of our members and it is possible I have oversimplified some aspects of this.

I saw a show on The Discovery Channel (I wanna say Myth Busters) that stated that if you hold a gun (particularly the barrel) parallel to the ground along with a coin at the same height as the barrel and fire the weapon, both the bullet and the coin will hit the ground at the same time because of GRAVITY! Gravity always has the same gravitational pull on objects.

However, I don't know if that applies to this example since we're comparing two bullets as opposed to one bullet and a penny!

Just my .02 cents!

Rifles are generally zeroed so that the bullet arcs upward before falling down. If it were aimed so the bullet was fired parallel to the ground, yes it would hit the ground at the same time as a penny dropped.

^^^ Very interesting. Thanks for the bit of knowledge there Gen. Geoff!

As a point of trivia, two objects dropped from the same height in a vacuum at the same time will NOT hit the ground at the exact same time. In addition to the gravity of the planet acting on each object, the gravity of each object acts on the planet. Larger objects have more gravity, and therefore will pull the Earth to them infinitesimally more than smaller objects.

Grey_Mana said:

As a point of trivia, two objects dropped from the same height in a vacuum at the same time will NOT hit the ground at the exact same time. In addition to the gravity of the planet acting on each object, the gravity of each object acts on the planet. Larger objects have more gravity, and therefore will pull the Earth to them infinitesimally more than smaller objects.

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Density also plays a large role in gravitational pull (refer to the enormous density and small size of a black hole) Not that it applies to bullets so much.

Regarding the question, a bullet fired parallel to the ground (as we perceive it -- really tangential to Earth) will begin to fall immediately, though not so much that the eye would see. The bullet with more muzzle energy and/or better ballistic coefficient will travel farther (flatter) before landing.

Interesting fact: If a projectile were fired at fast enough rate, it could theoretically fall with the Earth's curvature and continue indefinitely in orbit unless it hit something. Assuming it didn't burn and the atmosphere didn't change.

As a point of trivia, two objects dropped from the same height in a vacuum at the same time will NOT hit the ground at the exact same time. In addition to the gravity of the planet acting on each object, the gravity of each object acts on the planet. Larger objects have more gravity, and therefore will pull the Earth to them infinitesimally more than smaller objects.

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This statement is incorrect, the weight/density of the object does not matter if the object is falling in a vacuum. What Grey_Mana and DynamicPrecision refer to is Newton's Law of Universal Gravitation. Which defines force of gravity between two objects not the acceleration due to gravity mentioned below (which in the case of earth would be 9.8 m/s/s) Galileo demonstrated that objects fall at the same rate in a vacuum.

velocity = initial velocity + gravitational constant x time
v = v0 + a*t

The gravitational constant on the earth does not vary, therefore, since the above equation does not factor in any "resistance", objects falling in a vacuum will hit the ground at the same time if dropped from the same height. (i.e. if initial vertical velocity is zero). Things drop at the same rate 'beacuse the gravitational and inertial masses are equal for all objects."

Check out the video of the classic "feather and hammer" experiment performed on the moon.
http://www.youtube.com/watch?v=5C5_dOEyAfk

I double checked my work using this webpage that answers the same question from which the above quote is from.
http://www.physlink.com/education/askexperts/ae6.cfm

The link has a good amount of physics in it.

Back to the OP's original question:

KE (kinetic energy) - 1/2*m*v^2

It is this energy that causes most of the damage done by a bullet. So, a 9mm (124 gr) travelling at 1,000 fps is going about 2,000 fps slower than say a .25-06 running around 3,000 fps. Considering that their masses are close to equal we will neglect that difference. Now the difference in KE is the difference in their velocities squared.

This means that the ratio of KE of 9mm:25-06 will be about 1:9 meaning that the .25-06 rifle round has 9 times the KE of the 9mm

This is just an example and no is not 100% correct, but it is close under ideal conditions. At least I think it is, if anyone sees an error please give me a heads up

This statement is incorrect,

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Technically he is correct, in that the different masses of the objects being dropped will have an infinitesimally minute (and completely unobservable) effect on the rate at which they fall, since gravity is a derivative property of mass.

But the difference in acceleration is orders of magnitude under anything we could measure, even in a vacuum in a controlled laboratory environment.



Keep in mind, you also age more slowly while you're driving, because relative time slows down as your velocity increases. It's just not by any appreciable amount while moving at terrestrial speeds (even when on commercial flights). You also are technically pushing the earth down when you jump (equal and opposite reaction). Just not in any significant or meaningful way.

Interesting fact: If a projectile were fired at fast enough rate, it could theoretically fall with the Earth's curvature and continue indefinitely in orbit unless it hit something. Assuming it didn't burn and the atmosphere didn't change.

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You need about 11.2 km/second (or 36,700 ft/s).

Now you know why it takes staged rockets to reach orbit.

Also keep in mind that the gravitational constant is not constant, it is dependent on the distance to the center of the earth. There is a measurable difference in gravity at extreme differences in altitude.

Don't forget that the equator is also something like 20 miles further from the center of the mass of the earth than the poles (the earth is not a perfect sphere), and thus you weigh less at the equator than you would at the poles (not much, maybe a pound or two).

txhoghunter said:

Back to the OP's original question:

KE (kinetic energy) - 1/2*m*v^2

It is this energy that causes most of the damage done by a bullet.

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Kinetic energy is not always the best way to measure the damage done by a bullet, especially at the typical energy levels of pistol bullets. Some of it goes into creating a "permanent cavity" through direct contact with the bullet. This is how nearly all of the effective wounding is done by pistol calibers. In the case of expanding bullets, some of the energy goes into that process, as well. The rest of the energy is imparted to the surrounding tissue, pushing it outward in what is known as a "temporary cavity." With pistol calibers, the tissue will be stretched in this manner only slightly, and usually well within the elastic limit of most types of tissue (unlike ballistic gelatin, which is far less elastic and tends to be damaged quite readily even by low levels of kinetic energy).

Centerfire rifle calibers differ in that they usually have enough kinetic energy to stretch living tissue beyond its elastic limit, tearing it up even beyond where the bullet comes into direct contact with flesh. This is visible as a far larger temporary cavity in ballistic gelatin. There are other ways in which the greater energy of rifle calibers can be utilized to wound more effectively, but in terms of "stopping power" this is the primary reason they have more of it, while pistol calibers have to rely more on precisely where shots are placed (shot placement always matters, it just has to be more precise with pistols, and may take more hits). This should address the OP's question in the most generic of terms.

By the way, since no common pistol caliber has enough energy to wound significantly through temporary cavitation, which at least some people believe, the differences in their kinetic energy levels don't mean much in and of themselves. Some pistol calibers may well be more efficient and require less energy to wound a similar amount as another. For rifle calibers, kinetic energy is a more meaningful means of comparison, but it's hardly the be-all-end-all, either, since penetration can be critical when dealing with larger creatures.

One thing that makes a rifle more effective than a handgun is that it is faster and easier to hit with. Try shooting some common handgun drills like "devils hole" or "El Presidente" with an AR or a pistol caliber carbine sometimes. You will be much faster and more accurate.

I understand rifle rounds travel faster, but what does that mean to the target?

When you double the velocity of a projectile you 4 times the energy.

"With a longer barrel, rifles can develop higher velocities at lower pressures relative to a handgun, which requires more pressure (faster burning powder) to develop high velocities in a short barrel. "
Max pressure for 9X19mm is 35,000 psi. For 223, it's 55,000 psi. For 308 it's 62,000 psi.

"Rifle rounds such as the .223 have a higher sectional density than handgun rounds ..."
SD for a .224" 55 grain bullet is .157. 9mm 115 gr. SD is .130, 9mm 147 gr. is .167. Larger caliber rifle cartridges employ bullets with higher sectional densities. In 30 caliber, a 150 gr. bullet has a sectional density of .226 and 180 gr. .271.

Generalizations:
A rifle cartridge uses a larger case to hold more powder, which results in a bullet going faster and possessing more kinetic energy.
A 9mm case uses 5 to 8 grains of powder and a 4" or 5" barrel to accelerate a bullet to 1000 to 1200 feet per second, at which speed the bullet is carrying 330 foot-pounds of kinetic energy.
The 223 uses 25 grains of powder, a longer barrel, and a lighter bullet to produce 3000 fps and 1100 fp KE.
The 308 burns 45 grains of powder, uses the same barrel length as the 223, and a heavier bullet. 2800 fps with a 150 gr. bullet results in 2600 fp KE.

"Why are some rifle rounds considered adequate for varmints, some for large game, and some for dangerous game?"
Varmints - 223, small animals, not much penetration needed, small, frangible bullets work fine. High velocity results in a flat trajectory, which aids in making hits at longer ranges.
Big game - 308, bigger, heavier bullets, with more energy and higher SD, can deform to cause larger wounds, and still penetrate deeply.
Dangerous game - larger caliber, bigger, heavier bullets, more energy and higher SD, more penetration.

"Say one were to fire a 9mm round and a 5.56 round completely parallel to the ground on a completely flat range... If the rounds are fired at the same exact time, will the bullets hit the earth at the same moment (but hundreds of yards apart)?"
Yep.

And it’s easier to hit what you’re aiming at with a rifle.

A solid, non-deforming .223 bullet will produce a mild wound, compared to expanding and fragmenting bullets. This is the reason why FMJ ammo is generally unlawful to use for hunting game animals.

A .308 FMJ bullet at 2800 fps that penetrates soft tissues and exits without yawing or striking bone will produce a wound similar in severity to .32 ACP FMJ along the same wound track.

The same .308 bullet will burst a soda can filled with water while the same .32 ACP bullet will merely put a hole in it and maybe make it jump off the ground. The reason for the difference in soda can terminal performance between the two is because the .308 generates a higher pressure in the water which exceeds the capacity of the can to contain it. In soft tissues, however, the increased pressure doesn't produce increased wounding because soft tissues tolerate the pressure.

In 1997 the International Wound Ballistics Association reprinted an article by Elmer Keith titled: "Solid Bronze Bullets in the .220 Swift". Keith reported the lack of wounding effects of a solid, non-deforming bullet propelled at 3000+ fps against game animals.

The four components of projectile wounding are: 1) penetration, 2) permanent cavity, 3) temporary cavity, and 4) fragmentation.

Temporary cavity size can cause soft tissues to tear and rupture - creating greater permanent disruption as a result.

Bullet fragments weaken soft tissues which can allow the subsequent temporary cavity to tear open the small wound track created by the penetrating fragments - creating greater permanent disruption as a result.

Tissue type (the abilty to tolerate stretching) and the location of the tissue along the wound track in relation to the temporary cavity determines whether or not the tissue will be damaged by the effects of temporary cavitation.

Another question: do all bullets fall at the same speed? Say one were to fire a 9mm round and a 5.56 round completely parallel to the ground on a completely flat range. Say the 9mm would go 200M before hitting the ground, while the 5.56 would go 600M (guessing). Is this only because the 5.56 round travels farther in the time it takes for the earth to pull it into the ground? If the rounds are fired at the same exact time, will the bullets hit the earth at the same moment (but hundreds of yards apart)?

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All things, from a dodge caravan to a piece of cottonwood fluff, fall at the same speed in a vacuum. The only thing that will slow their acceleration towards earth is air drag.

Both bullets, if fired horizontal on a completely flat range at the same exact time, will hit the dirt at roughly the same time. There might be a tiny, insignificant difference but I doubt it could even be measured.

The 5.56 will go farther only because of it's increased velocity as you said. Mythbusters did a neat experiment where they fired a bullet from a gun and dropped a similar bullet right next to the gun, at the exact same time and thanks to high speed cameras you can watch them hit the ground at the same instant. Well actually 40 milliseconds apart but I think that had more to do with operator error than faulty physics.

Heres a video link for you...
http://www.youtube.com/watch?v=D9wQVIEdKh8

According to a test they did, a .45 acp will hit the ground after traveling about 360 feet when fired at around 3 feet off the ground. I figured it would have gone a bit farther.

This should clear it right up for you
The formula for calculating the ballistic coefficient for bullets only is as follows:[1][2]
bc=SD/i=m/i*d-squared
where:

BCBullets = ballistic coefficient
SD = sectional density, SD = mass of bullet in pounds or kilograms divided by its caliber squared in inches or meters; units are lb/in2 or kg/m2.
i = form factor, i = ; (CG ~ 0.5191)
CB = Drag coefficient of the bullet
CG = Drag coefficient of the G1 model bullet
M = Mass of object, lb or kg
d = diameter of the object, in or m

More effective as a defense weapon?

I heard a ROTC student proclaim that a handgun is the last line of defense, and if you're relegated to that, you're pretty much finished.

I always assumed he meant that, from a military standpoint, the rifle is full auto, whereas the handgun (Colt 1911 back then) is not.

Re your physics question, neither bullet will hit the ground if you hit what you're aiming at.

I would appreciate if any of Einstien's kin would chime in and help us with the physics!