Habu: Decent rate of bullets.
I have a penchant for physics (which makes firearms oh so much more fun) so I'll weigh in on Habu's question regarding decent rate of bullets.
They most certainly do not come down as fast as the go up. This has been already eluded to with the figure of 300fps but I'll give some non-math physics mumbo-jumbo behind it to back it up. Feel free the skip the lesson if it doesn't interest you. I already have a good feeling this might be a bit long.
Okay.... lets go.
Gravity's rate of acceleration is 9.8meters/second squared. If you drop an object (ignoring air resistance at this point) at 1 meter it will be traveling 9.8m/s.
Nevermind, we'll switch this to feet/second to make it easier.
9.8 meters == 32 feet.
and: v (velocity) = a (acceleration) x t (time)
Velocity is just speed with a direction. Everything in this case is going DOWN though so for all practical purposes velocity is equal to speed.
At one second the object is going 32 feet/second, at 2 secons the object is going 64, at 3 96, etc.
Assuming that the figure of 300fps is correct for a 150 grain bullet that means that it will reach maximum speed at 9.3 seconds. It maxes out because of air resistance. Imagine sticking your arm out the window of a moving car. Lets say you're a small child with a big hand and you have your hand cupped outside the window.... and you have enough stregth to deliver 30 pounds of force to that hand to meet the resitance of the air. At 10mph this is plenty of force to keep your hand out the window... at 80mph is becomes hard... and at 300mph there's no way you're going to be able to hold your hand out there. That's air resitance.
Every object in the earth's atmosphere will experience then when dropped from a height. After a while gravity (that 32ft/s squared force) just isn't pushing on the object enough to beat air resitance -- like your hand outside a window. So it balances out and the rate of acceleration drops to zero and the velocity (speed) remains constant.
We can do a little monkey business with the numbers now to figure out just how high the 150 grain bullet will have to go before going any higher is useless in regards to it's speed when it hits the ground.
d (distance) = t (time) + 0.5 * a (acceleration) * t (time) ^2
Knowing that 300fps is the max speed (it was measured by somebody) we know that t is 9.3, acceleration is always 32ft/s/s and that gives us:
d = 9.3 + 0.5 + 32 * (9.3^2)
d = 9.3 + 0.5 + 32 * 86.50 (rounded)
d = 9.3 + 0.5 + 2768
d = 2777.8 feet.
... I'm REALLY out of practice on this so if somebody wants to contest the numbers you're more than welcomed.
So, firing a 150 grain bullet up into the air can absolutely positively have no more force than if you dropped it from 2777.8 feet out of an airplane....
At first that sounds REALLY wrong but on second thought it's reasonable. The human body hits terminal velocity (assuming belly to the earth position) in 1800 or so feet and tops out at 176ft/s which is around 120mph. So, the round in question would come down at around 220mph but never go any faster than that.
If you feel that objects just MUST have to fall faster and faster contantly when thrown from such high heights I emplore to find the nearest dropzone, do the classes, get a parachute on your back and toss your butt out of a plane. Trust me... you stop going faster after a while and that's a WEIRD feeling to be thousands of feet in the air and not feel like you're falling.