Originally Posted By: Winny FanSo far, about all that most of the answers presented at this point do is allow an individual to arrive at one conclusion: Gunsmiths who are not trained as physicists should stick to being gunsmiths, and most likely, AND conversely, physicists who are not trained as gunsmiths should probably stick to being physicists.
Also, so far, the closest anyone got to a true answer without a lot of the usual internet fluff and bluster was the gentleman who mentioned terminal velocity. The terminal velocity of any object can be precisely determined, or it can be a best educated guess, based on the amount of relevant variables that are exactly measured. And the variables measured include gravity and atmospheric density which varies with altitude, water density in the atmosphere, temperature, ad nauseum, and the list goes on. In addition, the mass of an object and its shape as well as its flight characteristics while falling are other variables that fit into the equation to provide a final and definitive answer.
I will add the following response about a falling bullet in that it will typically fall mass first, which generally means the back end of the bullet will arrive first in atmospheric "free fall", unless there are other variables present which singularly or in combination overcome the form factor of the falling object.
The only other idea I will ADD to the mix is that if you fire a 30 caliber 165 grain bullet into the air at an angle perpendicular to the horizon, I don't want to be at the point where it comes back down and contacts WHATEVER IT FIRST CONTACTS, AND ABRUPTLY FALLS BELOW FINAL TERMINAL VELOCITY. It could hurt a bunch. A feather falling from the same height would probably hurt less unless it sticks you in the eye.
Below are some links that might explain the entire issue a bit better. No link is necessarily better than others, but they explain the same idea in slightly different ways.
http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html
http://www.ehow.com/how_8670126_calculate-terminal-velocity-falling-object.html
http://www.mdusd.k12.ca.us/northgate/Teachers/Muilenburg/Website2/Dynamics/DragNot.html
http://hyperphysics.phy-astr.gsu.edu/hbase/airfri2.html
http://www.newton.dep.anl.gov/askasci/phy00/phy00012.htm
http://www.education.com/science-fair/article/terminal-velocity-maximum-velocity-fluid/
http://www.wikihow.com/Calculate-Terminal-Velocity
http://www.jirvine.co.uk/Physics_GCSE/Physics_AQA/Physics_2A/p2aL6.htm
Gentlemen: Get out your calculators and as they say in NASCAR, start your engines.
By the way, Newton's Second Law mentioned above deals with the rate of acceleration of objects of different mass. Falling objects all reach terminal velocity if they fall far enough, and if no other forces act against the single force of gravity.
Thus, two objects of different mass will fall at the same rate, but only in a vacuum. The reason for that is gravity is the only reactive force acting on a falling object in a vacuum. Mass becomes irrelevant.
In the instance being discussed here, the bullet will attain terminal velocity in falling a lot quicker than will a leaf dropped from the same height due to variables other than gravity. Newton's 2nd says next to nothing about which object will fall faster unless related variables are different or they change during the fall time of each object.
Yea, that's all well and good, but the question still remains, "with all the rounds fired in the air, why aren't there more dead Muslems"? 
