Do heavier bullets drop faster than lighter bullets....


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GarandOwner
July 9, 2008, 01:36 AM
One great gun debate that has been brought up recently is whether bullets of a heavier weight drop faster than a lighter bullet of the same size. Many refer back to basic physics that states that in a vacuum two objects that are acted on by the same acceleration (in this case gravity) will move at the same rate regardless of mass or size. It is this concept that has led many to claim that bullets drop at the same rate regardless of their weight. However there is a key component missing in this claim. In the real world, we don't shoot in vacuums, we shoot through air. For this reason we must account for air resistance. Air resistance occurs from the flow of air around an object as it moves. In the case of bullet drop, there are two components of air resistance, a vertical resistance and a horizontal resistance. The only one that has an impact on the amount of time it takes for a bullet to hit the ground is its vertical resistance. One concept that carries over regardless of wither or not the bullet is moving through a vacuum or a fluid, is that a bullet that is shot parallel to the ground will hit the ground at the exact same moment as one that is dropped at the same time. For this reason we can examine free fall to determine if an objects weight is significant in the time it takes to hit the ground. It does use some higher level math (calculus and differential equations) but I tried to explain it simple enough that anyone can follow and understand.

First case: Neglecting air resistance

position, velocity and acceleration are all related to one another. Velocity is the derivative of position, and acceleration is the derivative of velocity, and the second derivative of position. First we will start by looking at acceleration. A bullet is generally fired no more than 6 feet above the ground, for this small variation we can neglect the changes in acceleration due to gravity since it is minimal (minimal meaning that it doesn't even change out to the one ten thousandth place holder. (.0001)) so acceleration is a constant g that is not dependent on time. As with all physics equations, we start with Newton's second law: F = ma where a force equals a mass times its acceleration. We know gravity, but we want to find it as a function of time. So we have:

ma(t) = mg

where m is mass, a(t) is the acceleration as a function of time, and g is gravity

We can see that mass cancels from both sides and we are left with:

a(t) = g

Taking the anti derivative (Integral) of acceleration we can get the velocity function. Since gravity is a constant it is a simple integral that evaluates as:

v(t) = gt + C1

Once again we can take the anti derivative to find the position as a function of time.

h(t) = 1/2gt^2 + C1t + C2

If we impose the initial conditions v(0) = Vo and h(0) = ho then this equation becomes:

h(t) = 1/2gt^2 + Vot + ho Where Vo is the initial velocity and ho is the initial position.


This function shows that an objects position is independent of its mass, so no matter the mass of the object, it will hit the ground at the exact same time. However this function has a flaw: it neglects air resistance, as we all know air resistance is significant. So let us start again including air resistance.

Second Case: bullet drop with air resistance

Air resistance is bv, where b is a constant that depends on the objects shape and the density of air, and v is the objects vertical velocity. Once again we get our basis for the equation from F = ma so this time we have:

ma(t) = mg - bv (air resistance is negative because it is an acceleration that "slows" the effect of gravity)

Once again to find velocity we must integrate with respect to time: It must be noted that this time our acceleration function has a velocity component, for this reason we can make it easier on ourseves by writing acceleration as the derivative of velocity with respect to time (dv/dt) so we have:

m (dv/dt) = mg - bv

by rearranging the equation we can make it more manageable to integrate

dv/(mg - bv) = dt/m

now we integrate each side, the left side is integrated with respect to velocity, and the right side with respect to time. So the equation becomes:

-(1/b)ln|mg - bv| = t/b +c where c is the integrating constant

we want to isolate velocity by itself so we multiply both sides by -b and take the exponential function of each side to help break down the left side this gives us:

mg - bv = e^(-bc)*e^(-bt/m)

which can be written as:

mg - bv = Ce^(-bt/m) where C = e^(-bc)

some simple algebra re-aranges the function so we have v by itself, this is:

v = (mg/b) - (C/b)e^(-bt/m)


by once again imposing the initial condition where v(0) = Vo we can solve for C. We see that when time is zero the exponetial term goes to 1 so:

Vo = (mg/b) - (C/b)*1

solving for C here we get that C = (Vo)b - mg plugging this back into our velocity equation yields:

v = (mg/b) + (Vo - (mg/b))e^(-bt/m)


It can be seen that velocity is a function that IS Dependant on mass when air resistance is included, so this means that the weight of a bullet DOES effect how fast it drops. Plugging in some simple values will show that an object of the same shape (same b value) with a larger mass WILL in fact drop FASTER than one that is the same shape but lighter.

For those over zealous mathematicians/physicists/engineers out there, you can integrate again and get the position function.

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razorblade31
July 9, 2008, 01:42 AM
True as far as it goes, but the fact is a heavier bullet is probably going to be a different shape than a lighter one. So the calculations you show cannot actually tell us if a heavier bullet will drop faster unless you come up with a satisfactory equation for b.

yeti
July 9, 2008, 01:45 AM
:what::eek::what:

ClickClickD'oh
July 9, 2008, 01:50 AM
Short answer: Possibly yes, but not to any significant extend considering the actual distance bullets drop in flight. Forward velocity of a bullet is much more important in determining bullet drop over range than vertical velocity is.

BammaYankee
July 9, 2008, 01:51 AM
Yeahh uhhh... Here's a thought... Put down the calculator, pick up a rifle, shoot different loads at 1000 yards, and see for yourself.

freakshow10mm
July 9, 2008, 01:51 AM
No, lighter bullets drop faster. They lose velocity quicker than heavier bullets.

MT GUNNY
July 9, 2008, 01:53 AM
:what::uhoh::scrutiny::confused::(

GigaBuist
July 9, 2008, 01:54 AM
this means that the weight of a bullet DOES effect how fast it drops.

Well, yes, but that doesn't have any appreciable meaning until you start reaching vertical speeds approaching the terminal velocity for the projectiles involved.

GarandOwner
July 9, 2008, 01:55 AM
Yeahh uhhh... Here's a thought... Put down the calculator, pick up a rifle, shoot different loads at 1000 yards, and see for yourself.


I cant, it rained today :neener:

No, lighter bullets drop faster. They lose velocity quicker than heavier bullets.

The velocity in this equation is the vertical velocity (down) not horizontal velocity

freakshow10mm
July 9, 2008, 01:57 AM
I don't speak math. I speak experience.

kcshooter
July 9, 2008, 01:58 AM
If you hold a bullet exactly the same as the one in the round loaded in your chamber at the same height as your chamber and drop it at the same time as the gun fires, the round shot from the barrel hits the ground at the same time as the one you dropped if your barrel parallel to the ground.
So the real test for this would be dropping a 55gr bullet and a 230gr bullet at the same time and seeing which one hits the ground first.

yeti
July 9, 2008, 02:11 AM
So the real test for this would be dropping a 55gr bullet and a 230gr bullet at the same time and seeing which one hits the ground first.
Well that one I can answer, they both hit at the same time.

PercyShelley
July 9, 2008, 02:16 AM
The velocity in this equation is the vertical velocity (down) not horizontal velocity

Lighter bullets would "drop faster" in the same, intuitive, trajectory-related sense that lower velocity bullets "drop faster", this is, they have more drop.

Also, "heavier bullets", at least within a given caliber is usually taken to mean longer bullets of similar density to the lighter bullets. Unless I'm missing something, these calculations seem to apply to a case where only the bullet's mass changed; which in the absence of a change of form means a change in density.

A longer bullet might well have a lower ballistic coefficient than a shorter one when measured sideways.

Seancass
July 9, 2008, 02:19 AM
ENERGY
Same speed, more mass means more energy. Since it has more energy, it will be less effected by the air resistance and will maintain it's high speed longer. (mass @ velocity, given air resistance produces deceleration)

Your math does seem to prove that a heavier bullet will drop faster, but energy says that the heavier bullet will also have a higher speed at a given range. So, does the substancial increase in energy over come the minute increase in downward aceleration?

I think a heavier bullet will actually have enough energy to maintain it's high velocity longer and actually appear to fall slower than a lighter bullet.

Benzene
July 9, 2008, 02:20 AM
BammaYankee, I fully agree with your method to "pick up a rifle, shoot different loads at 1000 yards, and see for yourself."

A rigorous mathematical analysis might be making too many assumptions. For example, how could it be 100% certain that deceleration is directly proportional to speed and not to speed-squared? What about turbulence factors of the medium (air)? And at these speeds and for a significant segment of the shooting population, is there a significant difference between likely drops?

Nice mathematical analysis, though.

RedLion
July 9, 2008, 02:26 AM
Dang it! You made me have to open my physics book and it is still SUMMER!!! but you are correct. Fluid resistance does change how stuff falls on the earth, thats why the astronauts bothered bringing a bowling ball and a feather to the moon and dropping them so to prove galileo's theory.

If there are any doubts, try dropping the bullets *sideways* in a fish bowl or something with water so the difference is more noticeable.

misANTHrope
July 9, 2008, 02:27 AM
Even if both bullets dropped vertically at identical speeds, given equal powder loads, the lighter bullet would drop less over a given distance due to increased horizontal velocity. Of course, that becomes less true the further downrange you get, because then you're moving into the realm of which bullet will retain velocity better... and I don't feel like trying to remember how to derive some real numbers there.

We can say for certain that equal forces of air resistance will decelerate a heavier object less. On the other hand, heavier bullets sometimes have different cross-sections from lighter- observe the difference between typical Core-Lokt .30-06 in 180 and 150 grain loads. The heavier load has a round nose. As for how much of an effect on drag that has? Beyond my ability to figure out with any kind of reliability.

In the end, modeling using mathematics will always involve assumptions of some kind, and will never be a substitute for real-world testing. But it's fun to think about. :)

justin 561
July 9, 2008, 02:30 AM
Even if both bullets dropped vertically at identical speeds, given equal powder loads, the lighter bullet would drop less over a given distance due to increased horizontal velocity. Of course, that becomes less true the further downrange you get, because then you're moving into the realm of which bullet will retain velocity better... and I don't feel like trying to remember how to derive some real numbers there.

Did they change the definition of vertical? I always seem to have thought it meant Up and down.

Am I the only one confused? Did Newtons law of Gravity change? No matter how heavy a object is, it's going to fall at the same speed regardless of weight when vertically dropped. If you mistyped and meant to type "Horizontal" then you're probably right.

Jimmy Dean
July 9, 2008, 02:38 AM
Umm, Mis, horizontal velocity has literally NO effect on bullet drop, in essance because the bullet itself produces zero list capability. IF the bullet produced lift, then horizontal velocity and vertical velocity would be related, but since it does not, they are not.

In relation to TIME, all bullets fired exactly horizontal will drop at exactly the same speed (this is for modern bullets, not round-ball bullets which can actually produce lift-like aerodynamic properties)

Now, over distance, differant rounds/loads will drop at a differant rate per amount of feet traveled foward, this is simply due to the fact that one bullet may travel 1500 feet in 2 seconds, whereas another bullet only travels 1000 in 2 seconds, and yet a third will travel 2000 feet.

At the 2 second mark, all bullets have dropped the same, but at the 1,000 foot mark, their drops are differant, because for the fastest bullet, that is only 1 second into flight, for the slowest, that is 2 seconds, it will have dropped signifigantly further by that distance.

gallo
July 9, 2008, 02:38 AM
GrandOwner,

It's been more than 8 years since I took a calculus class. From what I can understand, yes the weight of a bullet affects how fast it drops. However, two bullets of the same shape can be accelerated differently, as in the case of .357 magnum and a .38, and therefore drop at different rates.

Jimmy Dean
July 9, 2008, 02:43 AM
on edit to the air resistance, air resistance at points near 0 velocity is negligable. and remember, frictional forces act opposite of their opposing force, which means that the air resistance applied to the velocity of a bullet is almost all applied to the horizontal velocity, whereas the vertical velocity is essentially 0 at the start, and unless shooting from some seriously elevated position while shooting perfectly level, the vertical velocity will be mere meters/second when the bullet hits the ground. Also, strictly on paper, it would be essentially impossible to calculate the exact vertical air resistance affecting a bullet in flight, the reason is due to the spin of the bullet, and the effects of that spin and of the rifling grooves on the bullet

Lady with a Gun
July 9, 2008, 02:52 AM
It is very likely a light bullet, such as a 125 grain .30 caliber bullet will reach the target later, than a 180 grain bullet shot out of the same gun.

Why? Others have mentioned the lighter bullet will lose velocity much faster. So the lighter bullet will soon be travelling slower than the heavy bullet. Hence, it will take longer to reach the target.

If the bullet takes longer to travel to the target, it will drop further.

LightningJoe
July 9, 2008, 03:09 AM
No, lighter bullets drop faster. They lose velocity quicker than heavier bullets.


They're not flying; they're just falling. The smaller they are the more the air will affect them, so they'll fall slower. Also, they'll tend to follow a shallower trajectory to begin with (leave the barrel earlier so less affected by muzzle rise). Of course, they're zipping along at high speed, so the effect of air on them's probably going to be complex. Maybe not as straightforward as just dropping them.

Right Wing Wacko
July 9, 2008, 03:16 AM
I was told there would be no math!

Boomer
July 9, 2008, 03:17 AM
Here's my $.02. Imagine two bullets fired at a target at the same time and from the same distance. The faster one will drop less at target. This is because the distance the bullet drops depends on the time it is flight. More time ... more drop.

If the muzzle velocities of the two bullets are the same, and one slows down more than the other in flight, the one that slowed down more will take longer overall, and it will drop more.

The weight of the bullet doesn't necessarily determine which one is faster. There are lots of possible variations to consider, but one fact remains: the one that spends more time in the air drops more.

misANTHrope
July 9, 2008, 03:23 AM
Umm, Mis, horizontal velocity has literally NO effect on bullet drop, in essance because the bullet itself produces zero list capability. IF the bullet produced lift, then horizontal velocity and vertical velocity would be related, but since it does not, they are not.

In relation to TIME, all bullets fired exactly horizontal will drop at exactly the same speed (this is for modern bullets, not round-ball bullets which can actually produce lift-like aerodynamic properties)

Now, over distance, differant rounds/loads will drop at a differant rate per amount of feet traveled foward, this is simply due to the fact that one bullet may travel 1500 feet in 2 seconds, whereas another bullet only travels 1000 in 2 seconds, and yet a third will travel 2000 feet.

At the 2 second mark, all bullets have dropped the same, but at the 1,000 foot mark, their drops are differant, because for the fastest bullet, that is only 1 second into flight, for the slowest, that is 2 seconds, it will have dropped signifigantly further by that distance.

You've basically repeated what I was saying, except in perhaps a more coherent fashion. I think I tend to lose coherence the more I type.

:)

Snapping Twig
July 9, 2008, 03:32 AM
I thought Newton settled this particular debate centuries ago.

Everything falls at the same rate for a given weight.

Pound of feathers, a pound of lead... both hit the ground at the same time.

Happiness Is A Warm Gun
July 9, 2008, 04:04 AM
Boomer (and others) got it right.

All objects are accelerated towards the earth at the same rate (9.8m/s2).

Take two bullets.
Load one into a rifle and hold the other in your hand.
Keep both bullets at equal height.
Aim gun level to horizon.
Pull trigger and drop bullet in your hand.
Both bullets will hit ground at EXACT same time.

Horizontal velocity doesn't affect vertical velocity, acceleration, or displacement.

Bullet size, or weight doesn't affect vertical velocity, acceleration, or displacement.

So what does this mean?

At any point in TIME any two bullets will have dropped the EXACT same distance (vertical displacement) regardless of their weight, size, or muzzle velocities.

Since two bullets with DIFFERENT muzzle velocities will travel different distances down range in any given amount of time (say 0.1 sec) they will be at different distances down range for the same amount of drop.

Likely what the OP is interested in is:
At a static distance (say 50meters) which bullet drops more.
The bullet with FASTER VELOCITY will get their quicker. Since acceleration downward towards the earth is a constant it will have less time to fall and thus fall less.
Faster Round = less drop
Slower Round = more drop

Generally heavier rounds have lower velocity so they will drop more but this is due to the velocity not the weight, shape, or caliber of the round. If you took two rounds say 115gr 9x19 and a 230gr 0.45 and modified the powder load so they had exact same muzzle velocity they would have similar drop.

To back this up here is some data on my favorite SD rounds.

9x19 Federal LE HST 124gr
Muzzle Velocity: 1150 fps
Range: 25 50 75 100
Drop: 0 -0.9 -3.8 -8.8

9x19 Federal LE HST 147gr
Muzzle Velocity: 1000 fps
Range: 25 50 75 100
Drop: 0 -1.4 -5.2 -11.5

.45ACP Federal LE HST 230gr
Muzzle Velocity: 890 fps
Range: 25 50 75 100
Drop: 0 -2.0 -6.9 -15.0

.45ACP +P Federal LE HST 230gr
Muzzle Velocity: 950 fps
Range: 25 50 75 100
Drop: 0 -1.6 -5.9 -12.8

Notice the heavier bullet 9x19 bullet drops more but this is due to it's lower velocity. Since it travels slower it will be affected by gravity longer for any given range (25, 50, 75 yards) and fall more.

Compare that to the 2 .45 rounds. The slower 45 drops more than the faster 45 even though they have same weight. The +P 45 drops very similar to the 147gr 9x19 because they have similar muzzle vel 950 vs 1000.

You lost me. What does all this mean?
Pure and simple: faster bullets drop less. Regardless of caliber or weight the rounds with higher muzzle velocity will drop less for any given distance. Remember: ALL objects accelerate downward at same rate BUT the faster bullet hits the target quicker so gravity has less time to pull the bullet downward thus it doesn't drop as much.

EDIT: Air resistance does come into play however the time frames involved (<0.1 sec) and the aerodynamic shape of bullets mean that air resistance will be extremely minimal. Small variations in round crimp, bullet weight, powder measure will all have a magnitude more impact than air resistance.

jmr40
July 9, 2008, 08:42 AM
There is no mystery here. The question has been answered for decades, but to answer the question you first have to define long range. I will use the 30-06 as an example. Many hunters use the 150 gr bullet because it leaves the muzzle faster, around 2900 fps. They argue that since it is moving faster than a 180 gr bullet at 2700fps it will shoot flatter. Out to around 500 yards this is true. The lighter bullet will have about 7" less drop. 42" vs 49", assuming a 200 yard zero for both rounds. I'm using Remingtons ballistic chart for reference, using the most efficient loadings listed.

The ballistic chart stops at 500 yards and many people asume this trend continues but it does not. While the lighter bullet started out 200fps faster it also slows down faster and at 500 yards there is only about a 50fps advantage. Somewhere after 500 yards the heavier bullet will pass the lighter one and have less drop.

It really does come down to velocity. The faster a bullet is moving, the faster it will reach the target and the less time gravity has to work on it. It is just that at really long ranges a heavier bullet will maintain velocity better and will drop less than a lighter bullet. Like I said earlier you first have to define long range.

ranger335v
July 9, 2008, 09:04 AM
Actually, neither weight nor shape nor forward velocity mean a thing to the question as it was stated.

Both the light and heavy bullet will "hit the ground" at the same time. One may be much further down range but the drop time will be the same if they are fired on identical paths and over a flat surface.

There it is, no math! :)

Happiness Is A Warm Gun
July 9, 2008, 09:25 AM
Actually, neither weight nor shape nor forward velocity mean a thing to the question as it was stated.

Both the light and heavy bullet will "hit the ground" at the same time. One may be much further down range but the drop time will be the same if they are fired on identical paths and over a flat surface.

There it is, no math!

The bullets will always hit ground at the same TIME but not at the same place.

So velocity does matter if shooting at a fixed distance say 100m (or any distance). The slower bullet will hit lower. Why? because although the two bullets will fall/drop at the samw rate, the slower one will take longer to arrive.

Thus fire two groups from benchrest at 100m target. One w/ high velocity and one w/ low velocity. The one with low velocity will hit lower.

The drop is always the same based on TIME but since distance is based on velocity the higher velocity will have lower drop at ANY DISTANCE.

Weight doesn't matter directly ONLY velocity. Of course most heavier loads are also slower but it is the actual speed of the bullet not it's weight that causes the higher drop.

csmkersh
July 9, 2008, 10:25 AM
Long ago Galileo proved that objects of different weights drop at the same speed.

It's not that heavier bullets drop faster, it's that their lateral speed is slower and they drop the same amount in a shorter distance.

:banghead:

divemedic
July 9, 2008, 10:46 AM
Actually, a lighter bullet would travel faster in the horizontal plane, assuming they were of the same caliber. This means, that due to the curvature of the Earth, the bullet which travels farther in the horizontal plane will have to fall a longer distance to hit the ground. Therefore, a faster bullet will hit the ground after a slower, heavier bullet due to the curvature of the Earth.

:neener: See, I can do it, too.

yeti
July 9, 2008, 11:05 AM
Actually, a lighter bullet would travel faster in the horizontal plane, assuming they were of the same caliber. This means, that due to the curvature of the Earth, the bullet which travels farther in the horizontal plane will have to fall a longer distance to hit the ground. Therefore, a faster bullet will hit the ground after a slower, heavier bullet due to the curvature of the Earth.

:neener:See, I can do it, too.

Assuming the earth is round.:neener:

NCsmitty
July 9, 2008, 11:21 AM
The practical side of this discussion is that if you take two bullets of the same weight, one a flat base and the other a boat tail, and start them at the same muzzle velocity, the boat tail will drop less shooting in a 1000 yard match. Plain and simple aerodynamics. It's all about the BC baby.

NCsmitty

Seancass
July 9, 2008, 11:27 AM
i thought the origional question stated SAME SPEED. not same load. theoretical, different mass, same speed.

i think some people here are applying 8th grade science to college level physics and calculus.

And we're trying to argue about different things. a bullet dropped or a bullet fired? are we on earth or in a vacuum? are these bullets going fast and measured to perfection or rocks dropped by Galileo measured with guestimations?

Projectiles traveling through a fluid do not behave in pretty algebraic fashions. Making it that simple is just wrong.

kcshooter
July 9, 2008, 11:57 AM
Both the light and heavy bullet will "hit the ground" at the same time. One may be much further down range but the drop time will be the same if they are fired on identical paths and over a flat surface.Exactly. Bullet drop is a measure of distance, not time.

Happiness Is A Warm Gun
July 9, 2008, 12:13 PM
A lighter bullet doesn't automatically travel faster. The bullet muzzle velocity is based on the cartridge specs.

Some 0.45ACP +P 230gr have a higher velocity than a 147gr low recoil round.

The only thing that matters is VELOCITY of the round.
All objects fall at the same rate (i.e y axis acceleration is exactly same).


When shooting at a fixed target (1yard, 5 yards, 1000yards) the slower round will drop more. It is very simply due to the fact that the slower round takes longer to reach target therefore it is subject to gravity longer.

NCsmitty
July 9, 2008, 12:36 PM
I think if more people would apply practical ballistics and experience instead of trying to dazzle us with their prowess in "college level physics and calculus" theory, their proficiency at the range and in the field would possibly improve.
No one has addressed the hypothetical transition through transonic that may occur with one bullet weight and not the other, at least not at the same time. That may have an effect on the mathmatical outcome. We live in the real world where air resistance is different at subsonic compared to supersonic.

NCsmitty

Seancass
July 9, 2008, 12:42 PM
Exactly. Bullet drop is a measure of distance, not time.

Exactly. Acceleration has nothing to do with time.
wait....

dazzle us with their prowess in ... theroy
Theroy is easy, as shown by the calculations in this thread. It's reality thats complicated.

whosyrdaddy
July 9, 2008, 01:08 PM
IF the bullet produced lift, then horizontal velocity and vertical velocity would be related, but since it does not, they are not.


Not necessarily true. Given the relationship between the direction of spin and the direction of cross wind the bullet may indeed create lift. See Magnus effect.

Cosmoline
July 9, 2008, 01:11 PM
I thought how air resistance was a function of the BC, not the weight of the projectile. Thus you have excellent long range results with spitzer boattail rounds from the .50 BMG and even larger weapons.

whyipackmy45
July 9, 2008, 01:14 PM
No, they do not drop faster.

Zak Smith
July 9, 2008, 01:52 PM
The best way to determine what really happens (other than shooting) is to run one of the ballistic programs, set up the parameters of the gun and load, and try some different combinations.

You'll find that the combination of velocity and BC affect drop (as a function of distance).

If you want theory that works, pick up McCoy's magnum opus on external ballistics.

-z

MaterDei
July 9, 2008, 01:56 PM
Warning: My posts occasionally contain strong language (which may be unsuitable for children), unusual humor (which may be unsuitable for adults), and advanced mathematics (which may be unsuitable for liberal-arts majors).

You sig is very apropos.

ronaldbeal
July 9, 2008, 03:52 PM
Without checking your math in detail ('cause I'm lazy!)
The first fatal flaw i see with your work is the incorrect assumption that "air resistance" is BV where B is a constant based solely on shape and air density. What you are describing is "drag coefficient (http://en.wikipedia.org/wiki/Drag_coefficient)"
Instead of drag coefficient, you need to use "ballistic coefficient (http://en.wikipedia.org/wiki/Ballistic_coefficient)"
Remember, an object at rest remains at rest unless acted upon by an outside force.
BC takes into consideration the inertial resistance that a greater mass will have for a given DC. Ultimately, the mass components of BC will cancel out. DC will have a small effect on the acceleration due to gravity, but the result will be the same for any DC given different masses.
Hope that helps
RB

RPCVYemen
July 9, 2008, 04:11 PM
Wait a second. Isn't the "air resistance" that would effect the speed with which the bullet drops the vertical air resistance?

In other words, the air is resisting the bullet's motion in two directions. One is in the horizontal direction - slowing the bullet's flight towards the target. The other is in the vertical direction - slowing the bullet's fall to the ground.

As I recall - and I am a soft headed liberal arts type - air resistance increased with the square of the velocity of the object through the air. Now the bullet's horizontal velocity is very high and slows the bullet down dramatically.

But the bullet's vertical velocity is pretty low (the same as if you held the bullet at the height of the muzzle and dropped it). At that low velocity, isn't the air resistance going to be negligible?

Mike

CBS220
July 9, 2008, 04:16 PM
Excepting differences in falling velocity due to small factors such as the weight of the bullet (affecting the vertical velocity, not the horizontal), two bullets will fall at the same speed. And the difference due to the shape of the bullets is going to be minute- I'm sitting here dropping a .323, a .454, a .224, and a .257 and they are all impacting the desk at the same time.

More velocity will allow a bullet to get farther before it smacks into the ground, however.

If you drop a bullet at the same time you launch an identical one from the barrel of a rifle, both will strike the ground at the same time.

harmonic
July 9, 2008, 04:22 PM
Guess I shoulda paid better attention in physics.

ArmedBear
July 9, 2008, 04:25 PM
I see a little silhouetto of a man,
Scaramouche,scaramouche will you do the fandango-
Thunderbolt and lightning-very very frightening me-
Galileo,galileo,
Galileo galileo
Galileo figaro-magnifico-

http://www.ltc.arizona.edu/images/services_graphics_illustration.jpg

Zoogster
July 9, 2008, 05:07 PM
Drop is based on velocity, velocity over the length of the distance traveled. Since both bullets will have similar effects from gravity, the one that is traveling faster for the length of travel will have spent fewer milliseconds subject to gravity. Yet heavy bullets often due that better than the lightest loads.

The bullet is slowed by air resistance. The more surface area, and the shape of the projectile relative to its total mass determine how much it is effected.

Heavier bullets actualy tend to have more forward moving mass for a given surface area ratio. So even though thier initial velocity will be lower in the same loading, thier overall bullet drop over distance is less because at range they are going faster.

This is all factored into the ballistic coeffecient.
The ballistic coeffecient combined with initial velocity will tell you just how much drop you will have over distance.
Heavier bullets of the same shape will usualy have more mass without much more airflow resistance.
So they travel further with less bullet drop.

Obviously if it is so heavy it is significantly slower than a standard loading, then the initial velocity is a larger factor in that particular loading than the weight of the projectile.

There is a curve created by the pressure limitations of a loading. You will find the best projectile for a given range in that curve. Heavier than a certain point will drop more, and lighter past a specific point will drop more, at a given range, for the same shape and diameter projectile.

EYESOFTEXAS
July 9, 2008, 05:42 PM
I'm certainly no physicist, but my attempt at an answer.

First, maybe it's helpful to exaggerate the air resistance to illustrate the point.

1. Suppose the air resistance is so great that it instantly overcomes the horizontal velocity of the bullet and decelerates it to 0 fps. The bullet would drop straight down to the ground.

2. Now suppose the wind is so great that firing a bullet at it is like throwing a nerf football at a tornado. The bullet exits the gun but is instantaneously decelerated and, in fact, blown back at the shooter and dropped to the ground someplace behind him.

In either case, how FAST the bullet dropped was not a function of its mass. Air resistance in the vertical direction was also negligible. Consequently, both bullets dropped in the same time (i.e., they were airborne for the same amount of time). However, how far the bullet traveled in the horizontal direction (i.e., whether the bullet stayed in one place and dropped straight down or whether it actually fell to the ground someplace behind the shooter) was a function of the air resistance.

Overcoming air resistance is defined by the ballistic coefficient (BC) of a bullet.

If you assume the following:

* BC is proportional to the ratio of the mass of a projectile to its shape; and

* Higher BC means less deceleration of a projectile and lower BC means more deceleration;

then given two bullets with the same size, same shape, same muzzle velocity, but different mass, the heavier bullet will have a higher BC and will lose less energy over a given distance than a lighter bullet. This means it should (i) travel farther overall, (ii) have a shorter time of flight to XXX yards, and (iii) hit harder at XXX yards. However, it should be airborne for the same amount of time as a lighter bullet.

Of course, I'm sure somebody out there actually knows a whole lot more about this than me. For example, I think bullets start to nose down at some point in their trajectory and drag can actually contribute to bullet lift. But that's above my pay grade.

HGUNHNTR
July 9, 2008, 05:45 PM
Gravity is a constant, both bullets drop at the same rate regardless of size shape or mass. Drop a BB and a bwoling ball from the same height and both hit the ground at the same time.

AndyC
July 9, 2008, 05:48 PM
In a vacuum, certainly.

On planet Earth where air-resistance actually exists - different story.

Seancass
July 9, 2008, 07:45 PM
middle school science. college problem. this thread is fun.

Zoogster
July 9, 2008, 08:24 PM
Drop a BB and a bwoling ball from the same height and both hit the ground at the same time.

Only for a little while.

If you dropped them both from an aircraft at several thousand feet it would be a different story.

The BB especialy if lead would actualy be denser and might actualy have a higher terminal velocity than the less dense bowling bowl, and as a result hit first, though I would have to double check that with the stats of the ball. Normaly the much larger sphere would have the advantage, but the bowling ball is made from much less dense material.

The bowling ball would of course have more energy when it hit because it is significantly heavier.


Now if both were made of of the same material, lead to keep it simple, the larger sphere would have a much higher terminal velocity, and the lead size bowling bowl would still be gaining significant increases in speed long after the lead BB approached its terminal velocity.


So they would not hit at the same speed. The lead bowling ball size sphere would hit far sooner while the slow BB was still falling, its air resistance reducing its increases of speed from the gravitational pull long before.
The difference would be greater the further up they were dropped from.

This does not really relate to the OP's question though from a bullet fired at traditional angles, merely to your comment.

Hardware
July 9, 2008, 10:05 PM
Consider that we have two shooters shooting identical firearms with different weight bullets of identical shape. The lighter bullet is moving at 1150fps and the heavier bullet is moving at 750 fps.

Both shooters shoulder their weapons at the exact same height, firing across an absolutely flat surface. The lighter bullet hits the ground at exactly the same time as the heavier bullet. The lighter bullet is further from it's point of origin than the heavier.

The factors that are identical to both bullets are height of origin, or distance to fall to earth, shape of bullet, caliber, air resistance, and gravity, or acceleration towards the earth's core.

The different factors would be weight of bullet and velocity.

Depending on the accuracy of your measuring device the heavier bullet might strike the ground infinitesimally sooner than the lighter, because the heavier bullet's own gravity would have a stronger attractive force on the earth than the lighter bullet, but the difference would not be worth mentioning. No practical human measuring device could spot the difference.

Now get ye to a range!

akodo
July 9, 2008, 10:14 PM
The downward areodynamics of a bullet will affect how quickly it drops.

However, I don't see there being hardly any difference, especially when comparing two bullets of the same caliber, the heavier one just being longer. You have basically the same surface area due to weight looking at the bottom, and it isn' like the cone of air that forms around a spizter type bullet (which gave it such a nice range boost over older flat nose bullet types) you aren't going to have much of a difference at all in downward air resistance, so no difference per second of flight.

however, per unit of distance, because the lighter bullet is faster the time it takes to get from 0 to 100 yards is less, so less drop time

Zoogster
July 9, 2008, 10:23 PM
The factors that are identical to both bullets are height of origin, or distance to fall to earth, shape of bullet, caliber, air resistance, and gravity, or acceleration towards the earth's core.

Actualy air resistance is proportional to speed, and increases dramaticly the faster the bullet is moving. So the forces working to slow it down are stronger.

Both would hit the ground at the same time, as you said, and the faster one should be further.

You started with too extreme of a spread in velocity though, because to overcome that dramatic difference with an unknown weight (that might not be proportionaly different because you never gave it) a very long distance would have to be traveled before you would see a difference between different weight projectiles. Perhaps a distance greater than the distance they will travel at a 90 degree angle, that all depends on what the range of the cartridge is.

As I said there is pressure limitation that create a curve that you must know to demonstrate it.
A faster bullet travels farther, and hence has less bullet drop over distance. However it is the median speed you must factor in, not the muzzle velocity.

Over distance a heavier projectile of the same shape will have lost much less of its total velocity. So over a long enough distance the heavier projectile will actualy have less drop because it has a higher ballistic coeffecient, and hence loses less velocity, traveling further before impacting the ground. Essentialy meaning the heavier initialy slower round can actualy have a higher median speed over the distance of travel.
You need to start with less difference in speed though to realize it at practical distances. 1150fps vs 750fps is too great at realistic ranges at ground level, especialy at pistol ranges (which I assume you are comparing at those velocities).

At most pistol ranges the faster lighter round will usualy have less drop.
At long rifle ranges the heavier rounds with a slightly lower initial velocity operating at the same pressures will actualy have less drop than a light projectile going faster because the median speed of the heavier projectile can actualy be higher over its traveled distance because it bleeds velocity slower.

That is why there is a perfect bullet weight for a specific range at normal operating pressures (if accuracy was the only concern, obviously heavier rounds also penetrate better and retain energy better over distance, yet faster ones have higher initial energy figures operating at the same pressures.)

VirginiaShooter
July 9, 2008, 10:42 PM
Deleted. Nevermind.

Jimmy Dean
July 9, 2008, 11:09 PM
Zoogster, but those aerodynamic forces act in specific directions, yes, the faster, the more resistance, but BOTH bullets are starting with ZERO vertical velocity, their foward resistance is insignificant in relation to vertical drop.

Hud
July 9, 2008, 11:22 PM
Some may wish to download & read this, especially chapter 3:

http://stevespages.com/zip/canadian_b-gl-306-006fp-001%20-%201_june_1992.zip

Regards, Hud

GarandOwner
July 10, 2008, 01:51 AM
WOW what a turnout.....I worded the original post poorly so there has been some confusion as to what I am talking about, Let me try and clarify:

When I asked "Which will drop faster" I was referring to which one drops fast with respect to time, not distance. Since bullet drop is commonly referred to in shooting to be a function of distance I should have been more clear in my original post. The equations I derived were all functions of time not distance.



I thought Newton settled this particular debate centuries ago.

Everything falls at the same rate for a given weight.

Pound of feathers, a pound of lead... both hit the ground at the same time.

In a vacuum everything drops at the same rate regardless of size and shape because there is not wind resistance. However through air, the time it takes to reach the ground IS dependent on both the shape of the object as well as the weight. A good example: take a sheet of paper, see how long it takes to hit the ground, then ball it up and try again. The ball hits faster because its shape has less air resistance.


At any point in TIME any two bullets will have dropped the EXACT same distance (vertical displacement) regardless of their weight, size, or muzzle velocities.

Incorrect a heavier bullet will have dropped farther than a lighter bullet at a given time IF THEY ARE BOTH THE SAME SHAPE AND SIZE.

Long ago Galileo proved that objects of different weights drop at the same speed.

ONLY IN A VACUUM, through air both size and weight matter…don’t believe me, if size , shape and weight don’t matter and everything falls at the same speed, then how do parachutes work?....answer, air resistance. This opposing force is very small and in many cases (such as objects falling short distances) the difference is so small that it can not be observed by the naked eye, most of the work done with deriving air resistance came from the late 19th century, the main reason being that they did not have means that were accurate enough to determine this difference during earlier times ( ie Galileo’s time)

I think if more people would apply practical ballistics and experience instead of trying to dazzle us with their prowess in "college level physics and calculus" theory, their proficiency at the range and in the field would possibly improve.
No one has addressed the hypothetical transition through transonic that may occur with one bullet weight and not the other, at least not at the same time. That may have an effect on the mathmatical outcome. We live in the real world where air resistance is different at subsonic compared to supersonic.


1st, I am not trying to dazzle anyone just clear up the misconcetption people have that bullets drop at the same rate reguardless of weight, that is only true if you neglect air resistance, 2nd look up some of my range reports, my performance at the range is quite good (when Im having a good day :D 3rd, there is no vertical transition through sonic speeds, a bullet is being fired supersonically horizontally not vertically.


The first fatal flaw i see with your work is the incorrect assumption that "air resistance" is BV where B is a constant based solely on shape and air density. What you are describing is "drag coefficient"
Instead of drag coefficient, you need to use "ballistic coefficient"

Actually b in this equation is neither the drag coefficient nor the ballistic coefficient, it is a function of air properties as well as the shape of the object. If you try to use either the ballistic coefficient or the drag coefficient you will see that the units do not add up, your force equation will have units of velocity in it. b is expressed with the units N-sec/m (for metric) both the Drag coefficient and ballistic coefficient are unitless numbers.

Wait a second. Isn't the "air resistance" that would effect the speed with which the bullet drops the vertical air resistance?

Yes, that is the air resistance that is used in the original post, vertical air resistance, not horizontal


Everything that is usually taught in basic physics class is done ignoring air resistance. The reason: most kids taking physics haven't had differential equations or calculus yet!

Anyone who still disagrees with me that air resistance has an impact on the time it takes an object to reach the ground should try looking up "Free fall with Air resistance" I am sure that there are books out there that have the same equations I came up with. ( I know there is at least one, because way back when this was a test problem in my differential equations class ;))

Now I will restate the conditions for this statement to be true which will hopefully clear up any confusion that I created from my wording:

"Heavier bullets drop faster with respect to time than lighter bullets if both bullets are of the same shape and size"

Thernlund
July 10, 2008, 02:03 AM
Uh-oh. Line item quotes always spell the end of any meaning thread content.

I'm in awe this discussion has gone on this long, given the basic laws of gravity and all (that we learned in like 1st grade or something).


-T.

GarandOwner
July 10, 2008, 02:06 AM
Of course in the real world, bullets are different shapes and sizes so they all "fall" at different rates, vertical air resistance is so small that it is "washed out" by the fact that bullets travel at different speeds, so perceived bullet drop on paper comes from the fact that one bullet just "got there faster" so it didn't have as much time to fall. (which was covered by many previous posts)

Thanks to all that took an interest in these posts! :)

The main purpose of starting this thread was to inform people that because of air resistance all objects to not fall at the same rate. This misconception has come from forgetting the fine print in those basic physics problems that say "neglecting air resistance if two objects....."

Thernlund
July 10, 2008, 02:09 AM
Vertical air resistance is inconsequential for our purposes.


-T.

physics
July 10, 2008, 03:39 PM
Going to go ahead and agree with Garandowner on this one. There is definitely some interesting ideas on physics in here, that is for sure.
The main purpose of starting this thread was to inform people that because of air resistance all objects to not fall at the same rate. This misconception has come from forgetting the fine print in those basic physics problems that say "neglecting air resistance if two objects....." Ding ding ding! We have a winner!!!

rodngun
July 10, 2008, 03:50 PM
Will it hurt more if I hit you with a rock or a golf ball ???

robmkivseries70
July 10, 2008, 11:27 PM
Hey,
Once you guys added fluid dynamics (AIR) all bets are off, as it's too complex to predict; hence, all the counter examples. :uhoh:
Best,
Rob

Jimmy Dean
July 11, 2008, 12:12 AM
not really Rob, because the vertical air resistance starts off at ZERO since the bullets start with no drop. and since we are talking about shooting at an elevation of an entire 5 feet, it means that their vertical velocity when they hit the ground will be so slow, that air resistance vetically can still be counted as Zero.

bogie
July 11, 2008, 12:28 AM
Campers, it takes a few seconds with a ballistics guide. It ain't even rocket science.

Now, which weighs more? A pound of lead, a pound of copper, a pound of depleted uranium, or a pound of tungsten?

Sheldon J
July 11, 2008, 12:38 PM
It's all been said but the short version is...

Two rounds fired from different guns, example: one a 220 swift and the other a .45 LC. Both with identical trajectory, fired over a flat surface and fired at the exact same time, will hit the ground at the same time.

The primary difference will be the .45 will hit the ground about a 100 yards away and the 220 will hit the ground several hundred yards out, but that is due to the velocity of the round and not gravity which acts equally on all objects.

benEzra
July 11, 2008, 01:04 PM
Two rounds fired from different guns, example: one a 220 swift and the other a .45 LC. Both with identical trajectory, fired over a flat surface and fired at the exact same time, will hit the ground at the same time.
As long as both bullets leave the barrel traveling perfectly parallel to the ground. If there is any upward component of the velocity vector, then that will cause a longer flight time (up to several seconds).

benEzra
July 11, 2008, 01:05 PM
Now, which weighs more? A pound of lead, a pound of copper, a pound of depleted uranium, or a pound of tungsten?
In a vacuum, or in an atmosphere? :)

(Considering that the U.S. pound is officially a unit of mass, not weight.)

pappy
July 11, 2008, 04:42 PM
My brain's full, can I be excused? :confused::confused::confused:

GarandOwner
July 11, 2008, 05:30 PM
Two rounds fired from different guns, example: one a 220 swift and the other a .45 LC. Both with identical trajectory, fired over a flat surface and fired at the exact same time, will hit the ground at the same time.


:banghead: NO! NO! NO! the entire point of this thread was to debunk this misconception. Things DO NOT FALL AT THE SAME RATE THROUGH AIR! For bullets of different sizes the variable "b" must first be found, then it can be determined which will hit the ground sooner....I give up, I guess some people also believe that the earth is still flat :rolleyes: For such a short distance, they hit at nearly the same time, so close that you can not notice the difference with the naked eye, but they do hit at different times

Hud
July 11, 2008, 06:41 PM
Garand,

"You can lead a horse to water, but..."

Hud

Thernlund
July 11, 2008, 07:21 PM
NO! NO! NO! the entire point of this thread was to debunk this misconception. Things DO NOT FALL AT THE SAME RATE THROUGH AIR!

Repeat...

Vertical air resistance is of no consequence where this topic is concerned. We are talking about bullets. Not feathers. There is no meaningful difference between a .22LR and a .50BMG where vertical movement is concerned.

Two rounds fired from different guns, example: one a 220 swift and the other a .45 LC. Both with identical trajectory, fired over a flat surface and fired at the exact same time, will hit the ground at the same time.

All other factors being equal (shot angle, wind, ect.), that's exactly right.


-T.

Sunray
July 11, 2008, 07:54 PM
"...Do heavier bullets drop faster than lighter bullets..." No. Lighter bullets lose velocity faster, hence they drop faster.
"...Things DO NOT FALL AT THE SAME RATE THROUGH AIR!..." Yes they do. Gravity acts upon all things at the same rate. You could dig up Galileo and Newton and argue it over with them though. Or drop a 100 grain bullet and a200 grain bullet and watch them hit the ground at the same time.

Thernlund
July 11, 2008, 08:01 PM
"...Do heavier bullets drop faster than lighter bullets..." No. Lighter bullets lose velocity faster, hence they don't go as far.

Fixed it for ya. ;)

Regardless of velocity or weight, both bullets will move vertically at the same rate. They will differ in their horizontal movement only.

That is to say, they hit the ground at the same time, but at two different distances.


-T.

Funderb
July 11, 2008, 08:02 PM
Do heavier bullets drop faster than lighter bullets....



hahaHAHAHAHAHAHA.

THAT IS A JOKE.
IT BETTER BE A JOKE.

robmkivseries70
July 11, 2008, 08:40 PM
Hi Jimmy Dean,
I'll still have to disagree,as it is impossible to separate the bullet from the air. The bullet pushes air out of the way as it exits the barrel. The shape of the crown will affect the bullets path to some extent due to how the gases behind the bullet interact with the 'outside' air, and finally, the rotation of the bullet whilst traveling through the air is affected by the friction of the air molecules acting on the now "rifled" projectile. Now, I realize I am in the position of having to prove a negative :eek: so, I'll leave it at that. Back to the original question, and disregarding any aerodynamic effects, e.g. boat tail HP. Two projectiles, regardless of weight, leaving barrels at the same height above ground, at the same angle relative to the earth and at the SAME velocity will strike the earth at the same time and place. Meaning, the horizontal velocity and the vertical velocity due to gravity, are equal in speed and direction for each bullet.
Best,
Rob :)

just carl
July 11, 2008, 08:40 PM
Got tired of reading all the answers. Possibly some or most have some educational factors. However, all is just a probability and almost not able to be proven factually. Way to may variables. For example a bullets traveling through air at different elevations travel differently due to the density of the air. Bullets traveling through damp air versus dry air also travel at different speeds. Bullets traveling through air in motion towards or away from the path of the bullets also will have different speeds. If the weight of the bullets is even a thousandth of a gram different, there is a possibility of effect. If one bullet is soft and expands from the heat of movement from friction, that too could have an effect on the rate of speed of that bullet making it either fall faster or fly all over the place. A hollow point, ball point, flat point on one bullet versus another also play a part in speed and falling. Dropping a bullet at exactly the same micro second a bullet is fired from a gun is another just imaginable probability.
Just to many variables.

Jimmy Dean
July 12, 2008, 12:02 AM
rob, the other things that you are missing is this, bullets, heavy or light, are normally the same density as well, which means that despite their actual size, the effect of air resistance on them will be the same, since their size/weight differance will beproportional, so AR will act on them equelly

Orange_Magnum
July 12, 2008, 01:18 AM
How shall we now continue this discussion?

45crittergitter
July 12, 2008, 05:37 PM
The original poster and several others who agreed are correct, although I did not check all the formulas. Posters who noted that there is no practical difference in drop in air are also correct, as for a typical horizontal shot, we are talking about a drop of less than 5' from an initial vertical velocity of zero.

I would like to see a knowledgeable discussion of the effect of inertia on gravity-induced drop. Bullets in flight have considerable inertia, more so for higher velocities and faster twist rates. This inertia resists any change in motion. Stationary objects also have inertia, but not nearly as much. Like a gyroscope, a fast moving bullet is much harder to move off course than is a stationary one. Therefore, moving bullets should resist gravity more so than will stationary ones.

Comments by physicists/engineers?

DUCKNDAWG
July 12, 2008, 08:01 PM
The gravitational pull is the same no matter what the weight. It does not matter wether the bullet weighs 50gr. or 500gr. you shoot or drop them at the exact time and they BOTH will hit the ground at the same time!!!!

mpmarty
July 12, 2008, 09:30 PM
Everyone is right, and wrong.

All objects drop at the same rate IN A VACUME in our atmosphere a pound of lead will definitely fall faster than a pound of feathers, unless those feathers are compressed to a density of lead.

Heavier bullets have higher sectional density then lighter bullets of the same diameter. It is possible to streamline bullets of high sectional density with long pointed ogives and long boat tails like Berger does and others. These bullets suffer less velocity loss over long ranges allowing them to reach distant targets sooner and thus drop less.

In the real world anecdotal evidence is contradicting and confusing.
The same rifle, shooting the same weight and shape bullets can place its shots higher on a 100 yard target with a slower (less powerful) loading. This is due to longer barrel time and the rise in the muzzle during the bullets trip down the bore causing the slower bullet to launch at a higher angle of elevation or vertiacl azimuth. Downrage, at three or four hundred yards the slower bullet will impact lower as expected due to the flight time.

1911Tuner
July 12, 2008, 10:09 PM
Scientific revolution
Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th century and early 17th century. In his famous (though probably apocryphal)[citation needed] experiment dropping balls from the Tower of Pisa, and later with careful measurements of balls rolling down inclines, Galileo showed that gravitation accelerates all objects at the same rate. This was a major departure from Aristotle's belief that heavier objects are accelerated faster. [12] (Galileo correctly postulated air resistance as the reason that lighter objects may fall more slowly in an atmosphere.) Galileo's work set the stage for the formulation of Newton's theory of gravity.

Stevie-Ray
July 12, 2008, 10:49 PM
this means that the weight of a bullet DOES effect how fast it drops.

Well, yes, but that doesn't have any appreciable meaning until you start reaching vertical speeds approaching the terminal velocity for the projectiles involved.Alrighty then! Lets put in another twist. Say you're on a cliff and you can fire a 170 gr boat-tail spitzer straight out, and drop a 170 gr LSWC at the exact same time. Say a 15000 ft drop. This should be enough to get bullets falling at terminal velocity. Do they both hit the ground at the same time? Does anything change if both are spitzers? Both LSWCs?

Personally, I always thought that bullet design was to keep it in the air longer AKA aerodynamics. Then I hear that bullets don't have aerodynamics, but simple ballistic coefficient, as they produce no lift. I used to think that producing something akin to lift was the general idea in bullets like the BTS, to "ride on a cushion of air" so to speak. But then, I'm no scholar of any of the above sciences. Please explain, guys, this is fascinating.:cool:

1911Tuner
July 12, 2008, 11:11 PM
I always thought that bullet design was to keep it in the air longer AKA aerodynamics.

They don't stay in the air longer due to aerodynamics or coefficients of friction aka "Ballistic Coefficient" at all.

Let's compare apples to apples for a minute. Two .30 caliber bullets. One is a boattail spitzer, and the other is a plain based, round-nose bullet. Both bullets exit at the same velocity, and...if they're fired at the exact same instant...both bullets hit the ground at the same time. The boattail bullet will travel farther because it sheds velocity at a slower rate, so it's ahead of the round-nosed bullet when they hit the ground simply because it outruns it...and it's further downrange for a given unit of time in the air.

While there may be a difference in vertical acceleration between the two different bullet shapes...it would be so infintessimal that it would be of no practical matter.

Step up to two bullets of identical ballistic coefficient...but one is heavier than the other. If both bullets are fired at the same instant, and the exit velocity is identical...the heavier bullet will shed velocity at a slower rate due to its greater momentum, and it will outrun the ballistically identical, but lighter bullet...and they'll both hit the ground at the same time again.

Two identical bullets in every way...but with 500 fps difference in muzzle velocity. The faster bullet will travel farther than the slower one...but they'll hit the ground at the same time. One will just be farther downrange when it hits.

So, it's not a matter of dwell time in the air. It's the flight time to the target...the amount of time that gravity has to act on the bullet...at a given range that determines the amount of drop.

bogie
July 12, 2008, 11:37 PM
Figure in the curvature of the earth, and are you talking 1:7 twist or 1:14 twist?

Sir Aardvark
July 13, 2008, 12:07 AM
So everybody...

What do you think is Galileo's current rate of twist right now as he's spinning in his grave?

CNYCacher
July 13, 2008, 01:34 AM
Hold a heavy bullet in your left hand, and a light bullet in your right hand. Hold you hands out in front of you and drop them both at the same time.

/thread

chieftain
July 13, 2008, 02:14 AM
Folks remember your physics, all objects drop at the same rate.

ALL THINGS.

Now where it drops along it's trajectory, well now we can have a discussion. But they all will hit the ground at the same time. Just different places.

There used to be a physics experiment to prove this. It was called the monkey gun experiment.

Here read this link and learn.

http://www.fas.harvard.edu/~scdiroff/lds/NewtonianMechanics/ShoottheMonkey/ShoottheMonkey.html

Sheesh!

Go figure.

Fred

45crittergitter
July 19, 2008, 11:00 PM
False, except in a vacuum. The accelerational pull of gravity is the same, roughly 32.2 feet per second squared, but the rate of drop varies due to air resistance and ballistic/friction coefficient. Again, if you don't believe it, drop a muzzleloader ball and a plastic bag full of feathers (of the same weight if you wish) off your roof and see what happens. The fired bullet vs. dropped bullet thingy may work IF one can drop an identical bullet oriented in the same direction as the fired one (sideways) such that both drag coefficients are the same for a vertical fall.

Guns and more
July 19, 2008, 11:35 PM
The horizontal component has no effect. If it did the bullet would "sail" and not be accurate. Both a heavy bullet and a light bullet fall at the same vertical rate.
Therefore, FIRED HORIZONTALLY, from any height, they both hit the ground at the same time.

The fired bullet vs. dropped bullet thingy may work IF one can drop an identical bullet oriented in the same direction as the fired one (sideways) such that both drag coefficients are the same for a vertical fall.
The terminal velocity of both bullets is the same. That eliminates the air as a factor. Bullets falling orient themselves sideways. Mythbusters did this trying to see if a bullet fired straight up had enough energy to kill someone under them. They built a tube with a moving air column and the bullets fell sideways at about 150 mph, no matter what caliber.

gizamo
July 20, 2008, 12:14 AM
Gross oversimplification of course. But lets make it realistic.

Take a frisbee of 2 ounces and a 2 ounce round ball. Spin the frisbee on a horizontal axis and the round ball on a verticle forward axis and launch them at the same rate of speed through air. Which hits the ground first....

Ever seen a golf ball slice through the air, or a overspun round ball out of a musket ~ same effect. The air current effects the float. Musket balls can slice up, sideways, or down through the air.

But that 2 ounce frisbee can actually catch verticle lift and stay up there hanging for a good long while, often confusing the Border Collie waiting on it's return to earth:D

Giz

Dees
July 20, 2008, 12:31 AM
Ignoring air resistance, fat people fall at the same speed as skinny people. Now apply that to bullets.

gizamo
July 20, 2008, 12:49 AM
Good point,

For much of the theory given, you have to ignore air resistance.

Give either the fat person or the skinny person a parachute, and the results change dramatically.....

Can we all at least assume one given....
We do not live in a vacuum.....(well except for my wifes' checking account);)

Giz

GarandOwner
July 20, 2008, 12:59 AM
:banghead: I give up on this thread, too many people reinforcing false ideas. IN AIR objects do not fall at the same rate, not because of gravity but because of AIR RESISTANCE. All of the references to basic physics is referencing an IDEALIZED problem (which means air resistance is neglected) In the real world air resistance acts on everything. This is most evident in the classic case of dropping a pound of feathers and a 1 pound lead ball, a feather is not as aerodynamic as a ball, so it falls slower DUE TO AIR RESISTANCE. Now we look at two identical bullets, bullets are made to be aerodynamic, so their ability to overcome air resistance is great. When you drop two identical bullets, one that is heavier than the other, the heavier bullet will hit the ground first. HOWEVER the difference in time is so small that it is not humanly possible to percieve the difference.


Say you have a 55gr bullet and a 230 gr bullet that are of the same shape and size and you drop them at the same time from 5 feet. Using the position function that includes air resistance, we get that the 230 gr bullet will hit the ground in .5570 sec whereas the lighter bullet will hit the ground in .5582 seconds that is a difference of .0012 seconds or 12 ten thousandths of a second. The human eye can not observe this small of a time. That is why it seems that they hit at the same time, the spread between times decreases as height decreases
(ie they hit closer together if you drop them from a smaller distance)

Thernlund
July 20, 2008, 03:40 AM
In the real world air resistance acts on everything.

In the real world of objects weighing what bullets do, it doesn't matter. Drop a .22LR and an M1 Abrams from a height of 6 feet and they drop at the same rate. You cannot measure the difference in drop rate. Not with your eyes, not with a stopwatch. Vertical air resistance has no meaningful effect.

No... meaningful... effect. Period.


-T.

Guns and more
July 20, 2008, 09:42 AM
Stationary objects also have inertia, but not nearly as much. Like a gyroscope, a fast moving bullet is much harder to move off course than is a stationary one.

AAAARRRGGGGuuuu. A gyroscope will fall just as fast as anything else.

Guns and more
July 20, 2008, 09:45 AM
Quote:
Drop a BB and a bwoling ball from the same height and both hit the ground at the same time.
Only for a little while.

If you dropped them both from an aircraft at several thousand feet it would be a different story.

The BB especialy if lead would actualy be denser and might actualy have a higher terminal velocity than the less dense bowling bowl, and as a result hit first, though I would have to double check that with the stats of the ball. Normaly the much larger sphere would have the advantage, but the bowling ball is made from much less dense material.

The bowling ball would of course have more energy when it hit because it is significantly heavier.


Now if both were made of of the same material, lead to keep it simple, the larger sphere would have a much higher terminal velocity, and the lead size bowling bowl would still be gaining significant increases in speed long after the lead BB approached its terminal velocity.


So they would not hit at the same speed. The lead bowling ball size sphere would hit far sooner while the slow BB was still falling, its air resistance reducing its increases of speed from the gravitational pull long before.
The difference would be greater the further up they were dropped from.

This does not really relate to the OP's question though from a bullet fired at traditional angles, merely to your comment.

Boy is there a lot of misinformation here!!!

ryanl
July 20, 2008, 09:56 AM
As far as vertical drop. If you drop a bowling ball and a golf ball from 15 feet in the air they hit the ground at the exact same time. Not so close the eye cant tell, but the same time. I have seen this experiment more than once, and seen the camera slowed down enough to say with certainty it is the same time. To me this means all objects regardless of mass accelerate at the same rate. I do belive if dropped from an airplane the golf ball however would reach its terminal velocity before the bowling ball, therefore the bowling ball would hit the ground first. Just a WAG, but not much different then some of the stuff I just read in this thread.

gym
July 20, 2008, 11:56 AM
as a bullet slows down it drops, therefore if one bullet regaurdless of weight slows down faster, it will start to fall faster.

1911Tuner
July 20, 2008, 12:36 PM
as a bullet slows down it drops, therefore if one bullet regaurdless of weight slows down faster, it will start to fall faster.

Forward velocity ain't gotta thing to do with vertical acceleration.

Technically, bullets must be fired and dropped in a vacuum in order to strike the ground at the exact same instant...assuming that the bullet is dropped at the exact instant that the fired bullet gets free of the muzzle.

But...

In the presence of an atmosphere, and assuming that both bullets come under the influence of gravity at precisely the same instant...the difference in elapsed time to reach the ground would be infintessimally small.

GarandOwner
July 20, 2008, 01:47 PM
In the real world of objects weighing what bullets do, it doesn't matter. Drop a .22LR and an M1 Abrams from a height of 6 feet and they drop at the same rate.

You cannot say this with absolute certainty, you would have to test it.... Finding it would not be hard to do, Stokes equated fluid resistance in the 1850's you don't need high tech fast cameras to tell, you just drop both into a viscous fluid and calculate each's coefficient of drag, then replace the density of the viscous fluid with the density of air and you could find the difference in each through air. To say that at small heights objects fall at the same rate, but not at larger heights is foolish and doesn't make sense. Look at it intuitively: Why do some objects move slower through air? Because of the opposing acceleration of air resistance. It is there from the instant the object starts moving through air. It is smaller at low velocities, which is why from a small height the difference can not be perceived, but an object that encounters less air resistance accelerates faster (and this will hit the ground faster) than one that encounters more air resistance, even over a short period of time. YES it is small, but it is still there

No... meaningful... effect. Period.

This is a matter of opinion, while I do agree that this little difference would not effect, or even show up in your groups, it is still there. So to you it is not meaningful, but to a physicist or mathematician that like things exact, it WOULD be meaningful to them. Regardless OBJECTS DO NOT FALL AT THE SAME RATE. That you can not dispute truthfully. Even if the difference is milliseconds between when two objects hit, there is a difference so to say that they hit at the EXACT same time is false. Nearly the same time, almost the same time, true. Yes it is picky wording, but that small wording is the difference between what is correct and what isnt

As far as vertical drop. If you drop a bowling ball and a golf ball from 15 feet in the air they hit the ground at the exact same time. Not so close the eye cant tell, but the same time. I have seen this experiment more than once,

If you could reference some of these I would love to see them. On a high speed camera it might be possible to see the difference, but since 15 feet isnt very high, it would still be very close. The difference at such a short distance is very small, but there is still a difference there. So to say they hit at the EXACT same time is not true. To say that all objects fall at the same rate and air resistance has no effect doesn't make sense, how to parachutes work then? Why does a feather fall slower than a nail? So what you are saying is air resistance only acts on SOME objects? That doesnt make sense either, so who determines which objects experience air resistance and which dont? :scrutiny: Objects like spheres are aerodynamic, so they resist air resistance well, that is why it is hard to tell the difference in drop rates with them. While gravity acts on all things the same regardless of shape or size, air resistance does not.

I can see some people are set with their ideas even if they are incorrect, so I think it is pointless to try and keep arguing

Sheldon J
July 20, 2008, 08:21 PM
I think part of your confusion is you are assuming that a bullet with a larger frontal area will slow and drop faster than one one with a minimal balletic coefficient, which will have an effect on how fast they slow down once fired.

However as I said on my previous post... if they have identical flat trajectory, are fired at the exact same time, over a flat surface, and all else being equal except their mass, they will still hit the ground at the same time, and that is no myth

Zoogster
July 20, 2008, 08:24 PM
Boy is there a lot of misinformation here!!!

How do you figure?

The air resistance of a falling object is based on its surface area. The greater the mass for a given surface area the higher the terminal velocity it will reach.
The longer the object is falling the greater the difference between two objects with very different terminal velocities.

I could have phrased it with formula and kept it simple and brain dead, but some rambling that essentialy states the same thing is more fun.

You also stated

Bullets falling orient themselves sideways. Mythbusters did this trying to see if a bullet fired straight up had enough energy to kill someone under them. They built a tube with a moving air column and the bullets fell sideways at about 150 mph, no matter what caliber.

Multiple things done by mythbusters were wrong. In fact they did one of the greatest disservices to people that bought into thier falling bullet episode. They could not find most of the rounds fired into the air so they just tried to estimate and simulate it, but thier estimates were seriously flawed.

However just speaking of the "orient themselves sideways" myth, bullets often remain spin stabilized whe fired straight up and fall base first.
Bullets that do not stay stabilized tend to tumble. Most bullets from the side are not symetrical, the front is different than the rear. That means the air resistance effects one side greater than the other causing it to flip. So very few bullet shapes would fall sideways. Tumbling does slow falling rounds, while those that remain stabilized will achieve a much higher return velocity.

kcshooter
July 20, 2008, 09:10 PM
This has gotten stupid. There is so much good and bad info in this thread now that it can't be deciphered.
Galileo proved that they will fall at the same rate. They will hit they ground at almost exactly the same time. One will get further than the other based of energy and other forces, wind drag would fit in here. The rate that they slow down has nothing to do with the rate that they fall.

Don't take my word for it, I'm not a physicist, look it up.


http://www.pbs.org/wgbh/nova/galileo/expe_fobj_1.html

GarandOwner
July 20, 2008, 09:42 PM
In a real-life experiment, both balls would land at about the same time. (Friction from the air would change the result only slightly.)

From your reference kcshooter, note it says about the same time not exact same time and the reason is air resistance. As stated before, all things fall at the same rate in a vacuum, because gravity acts the same on everything. Air resistance does not act the same on all objects, it is dependent on size, shape, mass and velocity.

I think I need to bite my lip and just let this thread die........why am I so stubborn :p


Here is an excpert from something called "ask a scientist" two Dr's stated the same thing as I have multiple times in this thread:


http://www.newton.dep.anl.gov/askasci/phy00/phy00271.htm

The problem is that the shape of bullets are very similar and they are very aerodynamic so the difference in air resistance acting on them is so small that it can not be perceived by the naked eye, if you increased the height, it would be easier to see.

kcshooter
July 20, 2008, 09:47 PM
Yeah, but the air resistance being talked about thru this thread is resistance to forward travel, not downwards. And does it have to be exactly the same time, or is too close to be distinguished by the human eye close enough?

How much of a difference do you think there is in downward motion resistance from wind drag on, say a .223 vs a .308 dropped from 5 feet?? Enough to affect them to the point that one is actually going to land first? Doubt it.

Drop them both side by side. They hit at the same time. Fire them both side by side on a flat trajectory. They still hit at the same time. Forward motion does not affect this.

Funderb
July 20, 2008, 09:56 PM
I CANT STOP LAUGHING OH JEFUSS


this thread is ridiculous. is this really being argued?

Ridgerunner665
July 20, 2008, 09:59 PM
Velocity has nothing to do with how fast a bullet drops...it does have an affect on trajectory.

A bullet dropped from your hand and one fired from a gun...drop at ALMOST (meaning VERY, VERY close to the same) the same rate.

Heavier bullets drop faster...gravity makes sure of that....lighter bullets leave the gun faster, and travel farther faster...giving them their flat trajectory. The lighter bullets do slow down faster (less momentum)...

A simple test...drop a ping pong ball and a golf ball from the top of a building (the higher the better)...the golf ball will hit the ground first.

And a large part of the mass confusion on this thread is this...many of you have trajectory mixed up with drop....Trajectory is the bullets flight path...Drop is the amount the bullet drops without any correlation to the distance it has travelled

GarandOwner
July 20, 2008, 10:01 PM
Yeah, but the air resistance being talked about thru this thread is resistance to forward travel, not downwards.

If you read back, it is quite established that the velocity mentioned was downward velocity not horizontal

-v-
July 20, 2008, 10:04 PM
Will a larger (note: Not heavier) bullet drop slower then a smaller bullet?

Yes.

Will it drop appreciably faster then the more streamlined bullet? No, unless your shooting to such accuracy that a few nanometers difference in drop actually matters. Now if you're referring to POI, then yes, a slower bullet will drop faster then a fast one, because it has more time to drop then the faster bullet. But load up a light and heavy bullet to the same velocity, and interior ballistics (drag, etc.) and they will both drop the same exact amount.

Thernlund
July 20, 2008, 11:03 PM
We're a gun forum. Not a physics forum.

No... meaningful... effect.

I'm losing IQ points in spades just being near this thread.


-T.

CrawdaddyJim
July 20, 2008, 11:52 PM
This thread should have died at post 12.


Quote:
So the real test for this would be dropping a 55gr bullet and a 230gr bullet at the same time and seeing which one hits the ground first.
Well that one I can answer, they both hit at the same time.

I think some Italian guy figured this out back in the 1500s at some leaning tower in Piza Italy.

For a visual think of a spray of water from a sprinkler. The only difference is the distance from the head when they hit the ground.

Jim

mr.trooper
July 20, 2008, 11:53 PM
gravity stays the same. all object fall at the same speed.

don
July 21, 2008, 12:54 AM
Has anyone mentioned density? Assuming same shape,not size, two objects of the same density should fall at the same rate. Weight should be irrelevant as is horizontal velocity.

btaylor73
July 21, 2008, 01:32 AM
This thread has been an interesting one to read. I'm not meaning to stir the pot any more than it is, I just wanted to show an interesting thing that I saw on a vacation to Hawaii last year. On the USS Missouri I found this interesting sign mounted on their 16 inch gun mounts. What caught my attention was how fast the projectiles where moving. They where just as a bit slower than my .308 load at around 2700 fps. The interesting thing was the distance sometimes achieved with the monsterous rounds, 23 miles!!!
I know that my 308 would never come close to reaching 23 miles!
My conclusion has been, all things probably hit the ground at the same time when shot perfectly vertical, but as soon as the barrel starts rising the math gets too complicate. All I know is that my 308 doesn't shoot 23 miles

Ridgerunner665
July 21, 2008, 01:41 AM
Most average 50 BMG loads are also around 2,700 fps....

Thernlund
July 21, 2008, 02:54 AM
They where just as a bit slower than my .308 load at around 2700 fps. The interesting thing was the distance sometimes achieved with the monsterous rounds, 23 miles!!!

The angle of the shot and the weight of the projectile factor in. The angle, obviously, allows for a further shot. The weight causes the projectile to shed velocity slower. The net effect a much further shot.

All I know is that my 308 doesn't shoot 23 miles

It absolutely would if that little bullet weighed 2,200lbs.

http://en.wikipedia.org/wiki/16_inch_Coast_Gun_M1919

But that has no bearing on the (ridiculous) topic at hand. The .308 and the 16-inch rounds would both hit the ground at the same time when fired horizontally.


-T.

jakemccoy
July 21, 2008, 07:35 AM
I guess each person can come up with their own answers if everybody assumes different wind conditions. Let's assume a vacuum to keep this discussion under control. I'm obviously a little too late though.

gizamo
July 21, 2008, 08:00 AM
I like this discussion. Let's not limit it to the vacuum theory as the Original Post makes a comparison of only neglecting air resistance versus air resistance. Nothing is said about being in a vacuum.....

Let me ask this, as I shoot a lot of Cap and Ball. And maybe this will get us back on track with the OP...

Let's deal with sphere's....both fired horizontally at 6'....at the same weight and at the same velocity.

In Case 1: Negative Air resistance.
If I over spin a ball, it would still go straight and would have the same flight time before finding ground as a underspun ball.

In Case 2: Adding Air resistance.
Same overspun ball that slices upward through the air (as in a golf ball slice) And a underspun ball that just goes straight....

Obviously the effect of air resistance comes into play as the overspun ball gains altitude....

Do you think there would be.....no meaningful effect still?

Giz

Yooper
July 21, 2008, 08:32 AM
With respect to time, both bullets drop at the same rate, so they hit the ground at the same time. With respect to distance, the higher velocity bullet hits the ground at a greater distance than the slower one, but still at the same time. Gravity affects the projectile at a 90 degree angle with respect to direction of travel, so it has no effect on accelerating/decelerating the projectile, unless fired at an extreme up/downward angle, and then the effect is negligible, given ordinary bullet velocities. Air resistance is a constant, it affects the projectile in both directions, forward and downward. Bullet design affects travel through air and makes the bullet more or less efficient which allows the bullet to travel a greater or lesser distance, but it does not overcome the force of gravity.

Zoogster
July 21, 2008, 02:52 PM
Another factor is the arc the round is fired in.
Most rounds fired at distance are not fired at a 90 degree angle, but are fired with the barrel pointing slightly upwards giving a trajectory that zeros at a given range. A round with a higher BC, the heavier loadings, is going to spend more time going up before it begins to fall for a given elevation.
So since rounds are not fired at 90 degree angles at distance, a heavier bullet will actualy spend more time in the air before it would fall to the ground, because the higher BC of the heavier round gives it a trajectory that accomplishes that at a given angle greater than 90.

So while the sights may be aligned at a 90 degree angle, the barrel is actualy pointing slightly upwards. That means the heavier round with the greater BC will begin its vertical descent after more time has elapsed, being less effected by the horizontal air resistance when fired at a given barrel elevation.
So the heavier bullets will usualy actualy spend more time in the air. Meaning they have both less bullet drop over distance in a given caliber and spend more time in flight. It is however a mathmatical curve, you can change the results by using a round so heavy that it leaves at significantly lower velocity.
The curve depends on the given round.

45crittergitter
July 30, 2008, 10:02 PM
I guess next we will be hearing that centrifugal force is real. So for the record, it does not exist.

Jimmy Dean
July 30, 2008, 11:32 PM
oh God. its back. :P

GarandOwner
July 31, 2008, 07:05 AM
:: Loads the shotgun ::

Lets be humane and put this thread out of its misery, intelligent comments that furthered the thread ceased pages ago, let this one die.

Captal_de_Buch
July 31, 2008, 08:38 AM
I didn't think it was all that bad of a thread.

Those who didn't know about the gravitational constant are now aware that it exists.

Those who hadn't thought about the resistance of air to a falling object are now aware of it.

We all picked up little bit of knowledge.

Feanaro
July 31, 2008, 05:39 PM
Random information: Galileo Galilei probably didn't do anything with weighted balls near any towers. If there is any credence to his involvement in the gravity affair, it was likely a thought experiment. Not a very original one at that. Theories that contradicted Aristotle's notions of gravity and acceleration were floating around in Europe from at least the 1300's.

GRB
July 31, 2008, 05:43 PM
Yeah, okay, while you guys worry about this and figure it out, I am going to the range to see if I can keep it so the bad guy drops instead of me.

All the best,
GB

ilcylic
July 31, 2008, 07:23 PM
Sounds like your equations have more to do with volume than mass.

IndianaBoy
July 31, 2008, 09:09 PM
I'm not going to read the entire thread... but I presume someone else has already chimed in.,

Allow me a brief phsyics aside. It is not actually true that a feather and a bowling ball dropped in a vacuum fall at the same velocity. The equation that determines the force of gravity takes into account the mass of BOTH the earth, and the other object. Because of the way that equation works out, the mass of the earth is so much larger, that the other mass becomes technically (but not theoretically) irrelevant.




Back to the topic at hand.


If I shoot a 55 grain bullet with a high Ballistic Coefficient out of my 220 Swift, at say.... 3800 fps. And a 40 grain bullet at 4000 fps. By the time they have traveled 500 yards, the 55 grain bullet will be traveling faster, have more retained energy, and a flatter trajectory than the 40 grain bullet that was initially moving faster. It will probably catch and pass the lighter bullet if you could fire them at the exact same time.

onebigelf
July 31, 2008, 09:34 PM
Drop a bullet from a given height and fire an identical bullet from that same height at that same instant. Both bullets will strike the ground at the same time. Yes, a heavier bullet will fall faster. In addition, since a heavier bullet cannot be driven as fast in a given caliber, a heavier bullet will fall further at a given range since, traveling more slowly, it takes longer to reach that range.

Gravity, it's a law, not just a darned good idea! (is that language PC enough?)

John

langenc
July 31, 2008, 09:43 PM
What is heavier-a pound of feathers or a pound of bullets??

ASM826
July 31, 2008, 10:04 PM
Simply, the answer is no. Everything falls at the same rate. Slower bullets just go slower, so by the time they get to a target they have dropped more than faster bullets. You can demonstrate this with reloads. Use the same bullets, and load a minimum load and a maximum load. Shoot them at a target using the same sight picture.
Also, the rate at which bullets slow down, even if they were going the same speed at the muzzle, matters. If one is slowing down faster, then it's average speed to the target must be considered.
Lots of math involved. A lot of physics around acceleration, velocity, energy, and trajectory was worked out doing ballistics calculations in the middle ages.

Funderb
August 1, 2008, 11:13 AM
Stop!! This needs to go no further!!!!!

BAT1
August 1, 2008, 12:31 PM
I would think that a heavier bullet would have more momentum due to it's weight. I charged a 168 gr Sie and a 180gr bullet and shot them and they were hitting almost in the same spot on the target.

CNYCacher
August 1, 2008, 02:27 PM
Allow me a brief phsyics aside. It is not actually true that a feather and a bowling ball dropped in a vacuum fall at the same velocity. The equation that determines the force of gravity takes into account the mass of BOTH the earth, and the other object. Because of the way that equation works out, the mass of the earth is so much larger, that the other mass becomes technically (but not theoretically) irrelevant.
Here's a thought experiment for you: "How many times do you have to cut the bowling ball in half before all of it's parts dropped at once fall slower than the bowling ball fell when it was whole?"

Back to the thread at hand:
If you have a heavy bullet in one hand and a light bullet in the other hand, and you drop them at the same time, they will hit the ground at the same time. I urge you to try it yourself, even in your mind. You know as well as I know that if you dropped a shotgun slug from one hand and a .177 airgun pellet from the other hand, you are not going to be able to tell the difference on when they hit. Now, there is air resistance on falling objects, and this will affect the pellet more because the smaller an object gets, the greater it's ratio of surface area to mass. However, the air resistance to the two falling bullets is negligible in this case of dropping a few feet to the ground.

The same thing is true if you fired both bullets from two guns at the same time. If the barrels are level (which is not usually the case when shooting), and both bullets head out at the same time, their speed nor their mass make any difference at all about when they hit the ground. Where they hit the ground depends on their speed, because they have so much time to get as far as they can before they come to the ground.

In fact, if it were possible for you to fire a bullet from a level barrel, and drop a second bullet from the same height as the barrel at the exact same time that the projected bullet was fired, they would both hit the ground at the same time.

Feanaro
August 1, 2008, 02:50 PM
Here's a thought experiment for you: "How many times do you have to cut the bowling ball in half before all of it's parts dropped at once fall slower than the bowling ball fell when it was whole?"

In the atmosphere, just once... if you drop them from a high enough distance.

whosyrdaddy
August 3, 2008, 11:45 PM
Do heavier bullets drop faster than lighter bullets....

The correct answer is yes. Irrefutable proof comes in the form of the abundance of instances where aggressors have been felled instantly by a single haphazardly placed shot from a .45. On balance, the lighter 9mm routinely fails to drop at all despite multiple attempts and careful aim.

It's not just physics, it's the laws of physics.

Scattergun Bob
August 4, 2008, 12:41 AM
I mean YES

Test 1. Compare .224 Dia HPBT Match King Bullets

X1 = 69 Grain

Y2= 52 Grain

Givens:
VE = 3000 ft per second for both bullets

Distance to test point = 300 yrds

Data

Energy
X1= 700 Ft/Lbs
Y2= 400 Ft/Lbs

Bullet path

X1= -7.5 inches @ 300 yrds
Y2= -9.2 inches @ 300 yrds

Time in flight

X1= 0.35621
Y2= 0.38450


Looks like to make Y shoot to X will require minute UP elevation for the 52 grain HPBT Match King to strike at the same point as the 69 grain at 300 yards.

Thernlund
August 4, 2008, 12:54 PM
Looks like to make Y shoot to X will require minute UP elevation for the 52 grain HPBT Match King to strike at the same point as the 69 grain at 300 yards.They hit the ground at the same time when fired level to the ground. There is no meaningful difference. Due to velocity, they hit the ground at different distances.

Elevation changes the numbers by allowing higher velocity projectiles to stay in the air longer. It does not, however, change the laws of gravity.


-T.

gym
August 4, 2008, 10:48 PM
If 1 fat guy and one skinny guy running 20 mph, jump off a roof at the same time, will the fat guy hit the ground first?

Zak Smith
August 4, 2008, 10:49 PM
I think this is done.

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