What causes bullet drop?

That is not correct. bullets do not skate on wall of air like an airfoil, they receive identical force from every angle of the bullet shaft. there is nothing that could cause a bullet to drift upward or downward because of friction interaction with air.

bullets drop at the prescribed rate of 32fpsXX. It's that simple. The same goes for wind drift. High velocity bullets with low drag spend less time with gravity acting on them, pulling them down, and they spend less time interacting with wind, and being pushed down, or sideways.
 
...they receive identical force from every angle of the bullet shaft.
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That is correct as long as they are flying point first and there are no significant air currents impinging on the bullet from the sides.
...the only altering circumstances are air resistance to friction, and that is insignificant in bullets.
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That is generally a reasonably accurate statement for bullets that are falling in a normal fashion as long as they don't fall far enough to get close to reaching terminal velocity.

The statement needs to be qualified somewhat because air resistance does play a very significant role in terms of slowing down the bullet's velocity with respect to the bullet's travel along its aimed trajectory.
A bullet fired downward will have a certain velocity imparted by the rifle from the moment it leaves the barrel, and it will still gain downward velocity at the rate of G/.
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There will be a downward force acting on the bullet due to gravity. Whether or not the bullet gains downward velocity will depend on whether or not that force is greater or less than the force created by air resistance.

My best estimate is that the terminal velocity of a stabilized rifle bullet travelling downwards point first is somewhere between 500fps and 1000fps. If the muzzle velocity is greater than the terminal velocity, the bullet will slow down in spite of the downward force of gravity. It will continue to slow down until terminal velocity is reached.
 
See how your ballistics software calculates drop.

"Shoot" different caliber bullets with different weights and shapes different speeds going out level then check the drop values at 1.00 second time of flight.
 
See how your ballistics software calculates drop.

"Shoot" different caliber bullets with different weights and shapes different speeds going out level then check the drop values at 1.00 second time of flight.
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What would be the point?
 
To see if they all give identical results for the same inputs.

And see if their results match what a hand-dropped bullet falls in one second's time.

I'd bet they don't.
 
Enter sight height as zero inches, target range to 5 yards, range steps to 5 yards and max range to 1000 yards. Good enough for reasonable results.
 
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Here's the output from Berger's ballistic software for two bullets. Inputs are:

30 caliber 175-gr with G1 BC of .500
Zero sight height, 1 yard zero, 1 yard range step.
Max range 1000 yards and 70 deg. F.
Muzzle velocities 1600 and 2600 fps.

Drop after TOF of about 1.00065 second average as calculated for each muzzle velocity are:

1600 fps; TOF=1.0008 sec, range=446 yards, drop = 173.14" (14.43 feet) below LOS.

2600 fps; TOF=1.0005 sec, range=671 yards, drop = 164.19" (13.68 feet) below LOS.
 
16 feet the first second.
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That's right. Too long since physics class and too tired to think. Skipped a step.

The rough part about this is that no matter how precise the measurements are and how good the program is, air density, humidity, wind, all sorts of things can get in the way of computer projected trajectory tables and send them off a few MOA.

Modern snipers absolutely blow my mind. How a man with a rifle manages to make hits on a 12" diameter target at a mile is beyond me. It's like magic.
 
What if anything happens if I shoot my rifle at a range here near the 45th parallel, and then take it down to Ecuador to shoot it, where gravity is not as strong. Difference in time falling, farther shooting, etc.?
 
where gravity is not as strong. Difference in time falling, farther shooting, etc.?
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Probably not a measurable difference. While the force of gravity does vary depending on where you are on the earth and also with altitude, it doesn't vary as much as one might expect. As mentioned earlier in the thread, to get the force of gravity to decrease 10%, you need to be at orbital altitudes.
 
Drop after TOF of about 1.00065 second average as calculated for each muzzle velocity are:

1600 fps; TOF=1.0008 sec, range=446 yards, drop = 173.14" (14.43 feet) below LOS.

2600 fps; TOF=1.0005 sec, range=671 yards, drop = 164.19" (13.68 feet) below LOS.
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It's still pointless rambling
 
I've thought long and hard about what Bart B. is saying here, and I think that he is correct. To explain what Bart B. is getting at in more simple terms.

Bullets turn in flight. Bullets are both spin and drag stabilized projectiles. Everyone should know that bullets "nose over" in flight. A projectile that doesn't "nose over" in flight will destabilize shortly after the apex or maximum ordinate. The explanation for nosing over is that the net drag function on the base of the bullet pulls the base into alignment with the dominant air stream.

So a bullet fired completely horizontal will "nose down" during flight, and in doing so transfer the net drag function acting on the projectile to the top of the bullet.

I used JBM to calculate a 175 smk at 2650 fps with sight height of zero and zero range of 1 meter. Drop at one second (actual 1.074 seconds) was 15.4 feet.

A bullet with no horizontal velocity and simply dropped will fall at the rate specified for acceleration due to Earths gravity.
EDIT: 9.8m/s^2 is the acceleration equation.
distance = 0.5 acceleration x time is the distance equation (derivative of acceleration equation)

D = 4.9m/s^2 x 1.074^2 = 5.652m= 18.54 feet.

Simply put, the drag function that slows a bullet through the air is slowing the bullets fall towards the earth if it is fired horizontally. If there were no atmosphere there would be no drag on the projectile and there would be no difference.

On a physics forum several people noted that aerodynamics at high speeds throw off the ability of simple acceleration formlas to accurately predict reality. The three feet of difference between predicted drop by formula and calculated drop by ballistic software is a good example of this.

Jimro
 
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Are you certain about that?

I've heard that Gyroscopic stabilization keeps them on the horizontal, that they never alter their orientation, and that they just fall, staying horizontal, just as they would when dropped from a short distance. The thousand yard targets I've seen have never shown any evidence of a tilt.

In reality, a a pointed bullet would eventually tilt over to a base first drop due to drag on the lighter weight point, much like a shuttlecock would.

can you post some information that supports that?
 
Yes I am certain about that. X rays from the bodies of people struck by bullets fired up at extreme angles show the nose pointing down. Artillery shells have the fuze in the nose because even though they are fired pointed at the sky, the shell lands nose first.

Even footballs will nose over in flight when thrown correctly https://www.youtube.com/watch?v=tVoqA-LKGb4

If a bullet is over stabilized it won't nose over and this will cause destabilization. Conversely if a bullet isn't spun enough the center of gravity will try to flip forward into the center of pressure and the bullet will destabilize.

As to the reason you don't see oblong holes in targets is because bullets only flight minutely canted off line as the drag function pulls the base which forces the nose into the center of pressure. Our eyes have a very hard time picking up that imperfection in the target circle.

Jimro

EDIT: I knew someone had written it all down, took me a while to find it: https://www.precisionshooting.com.a...4/09/Twist-Rates-and-Projectile-Stability.pdf
 
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Most 30 caliber bullets fall about 1 to 1.8 inches per yard of range going through 1000 yard targets. Angle of fall is about 2 to 3 degrees. Their bullet holes are microscopically elongated vertically.

Military projectiles fired at angles above 45 deg. have been recovered nose almost straight down after penetrating armor. Their explosives are packed behind a hardened steel pointed penetrating shield. No penetration if the struck base first.

If bullets long axis angle to the horizontal stays constant through its flight, how does one calculate its ever increasing drag as it turns broadside to its path?
 
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Yes I am certain about that. X rays from the bodies of people struck by bullets fired up at extreme angles show the nose pointing down. Artillery shells have the fuze in the nose because even though they are fired pointed at the sky, the shell lands nose first.
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You are right. I knew all of that. Sometimes a person gets two different pieces of information or ideas and fails to fully integrate them both. That's what happened. I failed to connect the facts I knew, artillery, with the idea that I had read from an obviously unreliable source.

That is, unless artillery and bullets are so different that bullets behave in a manner contrary to each other, but personally, I think that you are right. Bullets and artillery are best friends that both behave the same. Even ICBMs swivel to keep the nose in a line with travel.
 
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