they all fall at the same speed regardless of mass.
No they have the same force exerted on thier mass. Since we are not in a vacuum the most important factor in the speed attained by a falling item is air resistance.
Denser items (like lead being one of the most dense) and shapes they reduce drag will fall much faster.
All items have the same speed added per second inititialy, but once they get going the less dense or less aerodynamic shapes have thier drag begin to slow them more than gravity speeds them up. They are at most of thier max speed very quickly.
A piece of lead however will continue to gain lots of speed for many more seconds before wind drag begins to slow it significantly.
The larger the piece the less surface area per amount of mass and even higher velocity will be attained.
Now shape is where it gets tricky as it effects its Ballistic Coeffecient. But the falling BC is very different than the BC of a fired round.
A sphere is simple, it goes up and comes down with the same resistance relative to its speed and the BC of the sphere is constant.
A bullet however goes up stabilized with a very high BC. On its return it can stay stablized and return base first like some do and attain extremely high velocity. Or it can tumble and attain a lower velocity because the tumbling down increases the resistance as some of its time is spent sideways.
Now all of this only the case going straight up and down. At an angle an even higher velocity is achieved because some of the original velocity is retained.
Now the funny thing about bullets going straight up into the air is that the energy of the falling round can be to a totaly different scale than the energy of the round going up.
What I mean is a more powerful round fired up can in some cases be less powerful returning. Heavier rounds will have more energy returning. So something like a shotgun slug will return with far more deadly energy than even a rifle bullet that had twice the energy when fired but is much lighter.
This assumes both projectiles go high enough that on return they have had many seconds to speed up( pretty much all bullets)
So many pistol rounds can actualy be just as deadly and sometimes deadlier than some rifle rounds in this situation because they have a higher weight, and return to earth with more energy even with less fall time. They are still fairly close though because the rifle rounds have almost twice the time to fall.
Terminal velocity is rarely reached, it is approached. Most of terminal velocity is reached within several seconds for most items, most of the remainder not long after, the final small percentage takes much longer.
So after a point significant increased fall time only adds slightly more speed. The faster the round goes, the more air resistance is created to slow it down. Eventualy the two would become equal and that would be the terminal velocity outside of a vacuum. However even the air density is different at different altitudes, and thier is also different crosswinds at different altititudes, so there is no exact answer, just a good approximation.
Just like while sky diving you can slow down or speed up by changing your shape, the air resistance plays the most important role in the terminal velocity. Put your arms and legs out and you are very unaerodynamic falling flat with high drag. Tuck in your arms and legs and go into a dive and you reduce your air resistance significantly and can go much faster. Yet your weight or mass never changed.
watched a Mythbusters episode where they tested the terminal velocity of different bullets and it was only enough to cause a bruise if it hit you.
Mythbusters was very wrong because they used the wrong formula to calculate the right terminal velocity of a lead bullet, especialy one falling base first still stabilized like many come down fired straight up.
So thier test firing at the pig head for example was at a significantly lower velocity than it should have been.
Just be safe. Probably more likely to hurt some one loading than shooting so just be careful.
