How fast does your bullet come down?

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stevegwynn

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Take a bullet, any bullet, point straight up with your rifle/pistol/firearm, fire.
If your muzzle velocity is 3000 fps, what will be the bullet's terminal velocity on the return to earth? I don't expect this is a trivial exercise in math / physics, but let's start with standard atmosphere pressure and temperature, and some common ballistic coefficient.

Anyone willing to help?
 
lysanderxiii said:
It will really depends if the bullet noses over and comes down point first, or if it doesn't and comes down base first.
Click to expand...

stevegwynn said:
Most bullets other than balls will act like an arrow, and rotate to point first due to air friction.
Click to expand...

Hatcher's Notebook, Chapter 20 -- Bullets from the Sky

Observations, not speculation. Well-stabilized bullets came down base first; marginally stabilized bullets tumbled and came down in random orientations. Terminal velocities clustered around 300 fps.
 
Okay, so let's say you point a firearm straight down from an extreme height. Will it hit the ground faster than when it left the bore? In other words is the drag caused by moving though ever thickening air enough to overcome the the additional velocity increase caused by gravity?
 
"Okay, so let's say you point a firearm straight down from an extreme height. Will it hit the ground faster than when it left the bore? In other words is the drag caused by moving though ever thickening air enough to overcome the the additional velocity increase caused by gravity?"

Drag from air resistance is the same regardless of the angle you shoot at. If fired downward from extreme height, air resistance will slow the bullet to the terminal velocity, which others up above have said is about 300 fps. Terminal velocity is the point where air resistance and gravity are balanced.
 
I've wondered about this from time to time. Someone explained that at some point, the bullet stops, and has to start it's trek back down. Now, all it has is gravity to overcome friction with the air. That always helped me understand why it doesn't come down at the same rate.

Now, what I just can't seem to wrap my head around, is how a ricochet can do a 180 and STILL come back with some force. I know it happens. Just trying to make sense of the forces at play at the VERY moment the bullet changes direction, especially when you keep in mind that it took a controlled explosion to get it all going in the first place. The velocity it has on the return trip, while not as great, is still quite considerable. Take this guy for example:

 
Rule of thumb; rifle held level to earth and fired, the time it takes for bullet to fall to earth is the same as if you dropped the bullet from the same height. Gravity acts the same on both bullets.
 
And yet every Independence Day, New Years, and assorted immigrant holidays, we hear of people being killed or wounded by bullets falling from "celebratory gunfire." I think the key here is that the drunken revelers aren't shooting straight up with a plumb bob, and their bullets are coming down in trajectory with a substantial residual velocity, not free fall terminal velocity.

Bullet bounce backs, as shown in the video at the extreme, are a result of an elastic collision. The steel deforms under impact, then springs back, throwing the bullet or fragments back whence they came. Then there is the deflection of bullets from dented or cratered hard targets.
 
jeepnik said:
Okay, so let's say you point a firearm straight down from an extreme height. Will it hit the ground faster than when it left the bore? In other words is the drag caused by moving though ever thickening air enough to overcome the the additional velocity increase caused by gravity?
Click to expand...

Back when jets were first entering service it was found that in a dive a fighter could literally shoot themselves down as they caught up to the bullets they'd fired. The bullets slow down very quickly but a jet under power can maintain its' speed and overtake them.
 
C5rider said:
Now, what I just can't seem to wrap my head around, is how a ricochet can do a 180 and STILL come back with some force. I know it happens. Just trying to make sense of the forces at play at the VERY moment the bullet changes direction, especially when you keep in mind that it took a controlled explosion to get it all going in the first place. The velocity it has on the return trip, while not as great, is still quite considerable. Take this guy for example:
Click to expand...

Stored energy in an elastic collision becomes the equal and opposite force in accordance with Newton's 3rd law. Just because something doesn't seem elastic or springy in terms of human touch doesn't mean it has no such action; Drop a hardened steel ball bearing on concrete and observe the results.
 
RecoilRob said:
Back when jets were first entering service it was found that in a dive a fighter could literally shoot themselves down as they caught up to the bullets they'd fired. The bullets slow down very quickly but a jet under power can maintain its' speed and overtake them.
Click to expand...
Actually, that was a fluke. The F11F had the guns mounted at slight positive angle relative to the line-of-flight, as did most aircraft. In one firing test the F11F fired a long burst in a shallow dive, then hit the afterburners and nosed over into a steeper dive. His burst of bullets on an upward trajectory took the long route, while the fighter taking the straighter line wound up under his own stream of bullets. Even though the bullets we're just TP, two struck the aircraft, one in the canopy, one in the engine, killing it.

The bigger problem with fast aircraft is strafing at too shallow a dive angle, risk flying over richochets, minimum dive angles and climb out angles are set to prevent this.
 
There are 3 cases to consider, all with different outcomes.

Fired more or less straight up, the bullet will go straight up, stop for an instant at the top and then either tumble on the return trip or fall base first.

If it tumbles, terminal velocity will likely stabilize somewhere around 150fps. This is not likely to be fatal although with very heavy bullets I suppose it could be dangerous to get hit in the head in this scenario.

If it falls base first, the terminal velocity will be much higher, possibly between 300 and 400fps. That is not high velocity by firearms standards, but it has the potential to be fatal depending on the circumstances.

If it is fired at a steep angle, but not straight up, the bullet will tend to follow a very tall arc, nose over and come down on a ballistic trajectory. It will have a vertical velocity equal to terminal velocity which will be higher than the base first scenario since bullets tend to be much more streamlined traveling nose first. In addition, because it wasn't fired straight up, it will also retain some horizontal velocity. The total impact velocity will be the vector sum of the horizontal and vertical velocities and it's difficult to nail down the velocity other than to say that it will be higher, probably much higher than the base first scenario velocity.
 
BTW, the generally accepted velocity for a projectile penetrating unprotected skin is around 400 ft/sec.
Eyes would be less. Don't know about skulls.

Biggest hazard from firearms discharged into the air are those shots that are not straight up.
Most folks engaging in such activities don't have a two axis level attached to their barrel.

"Authorities said Yoder was clearing a round out of his .50-caliber muzzle-loading rifle following a hunting trip when he fired a shot into the air."

https://www.cbsnews.com/news/amish-...ith-stray-gunshot-will-serve-30-days-in-jail/
 
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