If a rifle, say a 7 MM, were to be fired straight up, at what MPH would the projectile hit the earth?
About 200mph, according to a 1920 US Army Ordinance study.
If you fire a bullet straight up, it will go up until it stops, and then it will freefall back down, increasing in speed until it reaches its terminal velocity. A bigger heavier bullet will fall faster and will cause more damage when it hits. Handgun rounds are pretty light and probably wouldn’t hurt you all that much. Rifle rounds like the 7mm are heavier and would be a bit more painful. Wikipedia sites 300 to 500 feet per second for a .30 caliber and .50 caliber round, both of which are fairly big and heavy rounds. The 7mm is smaller than the .30-06 so it would be on the lighter side of those. I’d guess somewhere around 200 to 250 feet per second.
Fire the rifle an an angle though and the bullet follows a parabolic arc and can easily have a fatal velocity when it returns to earth.
As noted on news reports, falling bullets can be very dangerous.
Any fired bullet that is falling straight down that was originally shot at an upward angles as such to give it time to be coming straight down, ( no more push from the powder burn in the barrel ) will only be going at it’s terminal velocity.
A .38, .45, or even a .22 bullet you do not want to strike you on an unprotected head at terminal velocity. Ask any construction worker on high rise buildings how small an object can be and still be fatal.
If you just have to shoot in celebration, shoot right in front of your feet in dirt. Eye protection or other protection is optional. Just do not want innocents hurt.
The noise is not really noticeably less for celebration purposes. IMO.
And with any luck, they hit their own foot.
Mythbusters tested this. They concluded that at terminal velocity a bullet falling straight down probably isn’t (guaranteed to be) lethal, though it would certainly cause injuries.
I suspect most of these celebratory bullets don’t come straight down.
Out here, in the wild West, it’s a felony offense to fire a gun in the air.
This made me wonder if people are ever injured by falling bullets, because all I’ve ever heard of are people being killed by them. Turns out there’s a whole wiki page on celebratory gunfire. Apparently the mortality rate is about 32% compared to 2-6% from normal gunshot wounds.
The high mortality rate will be due to the fact that falling bullet injuries are generally head injuries, as opposed to general gunshot injuries.
Nitpick: My understanding is that this is not the case. A heavier bullet would cause more damage due to its greater inertia, but it falls at the same speed. (Ignoring wind resistance.)
Regards,
Shodan
A heavier object doesn’t accelerate any faster than the lighter one, assuming equal wind resistance, but terminal velocity, the maximum speed anything falling will reach, given enough time, IS dependent on mass, as well as a slew of other factors (wind resistance being high up there, too.)
A feather and a hammer will fall at the same speed (ignoring wind resistance). I know which of the two I’d prefer to fall on my head.
Or in other words, maybe this isn’t one of those scenarios where it’s appropriate to ignore wind resistance.
Ordinance study? Was this the ordinance in question?
(Nitpick: “ordnance” is weaponry, “ordinance” (note the “i”) is law.)
This isn’t physics class. You don’t get to ignore wind resistance here. In fact, my understanding is that wind resistance plays a pretty big role in determining terminal velocity.
It’s been studied using ballistic software.
Haag, Lucien, “Falling Bullets: terminal velocities and penetration studies,” Wound Ballistics Review, v2#1, p21-26.
Based on his table, I’d guess around 300 fps. Really not enough to kill, as 300 fps can be enough to penetrate skin, but you lack any meaningful penetration. I’d post his data table, but I can’t get it formatted here.
Falling bullets become lethal because they’re rarely fired straight up. They generally have an X velocity component as the weapon is fired at an angle.
A very recent case: http://www.cnn.com/2012/01/01/us/florida-celebratory-gunfire/index.html?iref=allsearch
Shannon would disagree with you.
If only there were a popular website where questions such as this could be addressed by the World’s Smartest Human [sup]TM[/sup]. 
That’s why I mentioned the greater inertia of the heavier bullet.
As far as wind resistance is concerned, wouldn’t a larger bullet present a greater surface area, and therefore accelerate slower? Also, the greater mass of the heavy bullet would mean that it didn’t go up as high as a lighter bullet would, so it would be falling back to earth over a shorter distance overall.
Actually, if I remember my physics, I should say it would be falling back to earth over a shorter time.
Regards,
Shodan
Or shotguns with #8 shot. The stuff only stings when it comes down (yes, I know that first hand).
Better still, get some damned fireworks.