Mythbusters: bullet fired vs. bullet dropped video...

I did watch this interesting video by the Mythbusters gang.

I believe it is in 4 or 5 parts, first segment is here:

https://www.youtube.com/watch?v=2tiOmp1BE8Y


I did not expect dramatically different results but I was a bit surprised that the fired bullet did not generate any kind of lift whatsoever....the two bullets touched the ground at the almost exactly same time.

Granted, because of space concerns they performed the test on a 1911 45 ACP pistol, low speed cartridge, not particularly aerodynamic bullets (round nose FMJ) inside an empty and long San Francisco warehouse.

Do you think the test performed with a FMJ spitzer bullet fired from a 308 or a 30-06 would have yielded exactly the same results or these very aerodynamic bullets would generate a bit of lift??


So bullets drop indeed, they do not fly.....

 

Of course. The only vertical force on a dropped bullet and a bullet fired from a level barrel is the force of gravity. The same force on the same mass equals same acceleration downward.

 

Of course bullets don't 'fly'.
How could they?

They are round, and spinning rapidly.

So any aerodynamic lift would be as likely toward the ground as toward the sky.

They start falling as soon as they leave the barrel (which was all that was holding them up.)

Remember Sir Isic Newton and the apple from grade school science?

https://www.york.ac.uk/physics/about/newtonsappletree/

rc

 

As they said in the intro, this is a textbook physics problem. The vertical force of gravity in the Y axis is the same no matter how fast an object is travelling horizontally in the X axis.

 

Not to be nit picky, but the mass is irrelevant. They will accelerate towards the ground at the same rate. One could have been a 115gr 9mm and the other a 230gr .45, and they still would have hit the ground at the same time regardless of which one was dropped and which one was shot.

 

I am going to say, had they shot a 22lr into a headwind, the dropped bullet would have hit the ground before the inflight bullet.

This is based on my experience shooting 22LR match bullets in small bore prone competition. I have seen the bullet impact go up with 12 0'C puffs of wind. These 22 LR bullets are ballistically inefficient, I think on a par with spit balls and tissue paper. Every puff of wind causes the things to float with the wind, which is why wind separates the men from the boys in Smallbore prone.

Gravity of course is real, and in a vacuum, it is simple to model drop speed. However there are media, such as air, (planes anyone) and water (surfboards), that will effect the drop rate of an ballistically inefficient object.

 

I said as much, though I agree my explanation was confusing. The force of gravity is the same, so, yes, objects of any mass accelerate down equally.

 

Uhhhh....no.

Now, I believe that your bullet hit high, but it's because the barrel of the rifle is angled upward and the wind is pushing against the bottom side of the bullet nose

 

In a vacuum yes, in the real world atmosphere not, you have to take into account aerodynamic drag.

 

True, real world atmosphere does play a role, but in this particular case it is so insignificant it can be disregarded. Now, at a higher drop distance with different test subjects it will make a world of difference.

 

The only difference I can see in the atmosphere vs. vacuum situation is the slightly different drag coefficients caused by the change in profile of the bullets.

The only motion that is relevant is the vertical motion.

In the atmoshpere:

For the dropped bullet, dropped nose down, the ballistic coefficient is well known. It is the "published number".
For the fired bullet, travelling nose first in a horizontal direction and "sideways" in the vertical direction, the ballistic coefficient will be different and larger.

For the relatively low vertical speeds this difference should be absolutely minimal.

In a vacuum, the orientation of the bullet will not matter since there is no aerodynamic drag.

Dan

 

No bullets won't "lift" like a wing of a plane or a aircraft built with a lifting body. But if your real good you can curve them. Just be careful you don't curve it so much you shoot your own butt.
https://www.youtube.com/watch?v=lGZQi3ODB-U

 

Mythbusters: Proof that a 10 minute show can be made to last an hour.

 

But, a higher BC will not change the acceleration of gravity.

A bullet with a high BC will go further, faster, before it hits the ground.

But, fired level with the ground, it will in fact hit the ground at the same exact time as one dropped from the same height at zero forward velocity at the muzzle.

rc

 

Absolutely true. An exaggerated situation -- a lead slug and a large feather weighing the same won't hit the ground at the same time if they are dropped from the Empire State Building at the same time.

They would though if they were dropped in a vacuum however.

Given the high rotational velocity of a fired projectile (~250K RPM or so?), I could definitely see how geometric differences in the projectiles could cause enough of a difference in drag to cause differing "drop times" -- if one had sophisticated enough instrumentation to record the differences.

 

But the vertical aerodynamic drag of two projectiles flying (or "dropping" if you prefer) through the atmosphere could be different enough to determine where they ultimately land. The difference might be tiny and the MB's may have not had the instrumentation to accurately measure the difference, but it exists.

32 feet/second/second is in a vacuum...

 

I'm not talking about a falling projectile with respect to the ground. I'm talking about two projectile dropping to Earth compared to one another.

The feather with the same mass as the slug isn't going to hit the ground at the same time -- unless both bodies are under a vacuum.

 

Sorta sad how people keep trying to conflate the X and Y axis here.

Like it or not, different things don't fall to the Earth at the same rate unless they are in a vacuum. A lead bullet projectile with a mass of 1 slug (pun intended) will hit the ground before a large feather also with a mass of 1S. The projectile is cleaner aerodynamically and accelerates faster. The feather would float to some degree.

Now the difference between two geometrically different lead projectiles of the same mass over say 5' of vertical drop would be infinitesimally smaller but there would still be a difference.

Odd some cannot grasp that and continue to attempt to pull the horizontal component into into play to muddy things up.

 

Bullet lift.....