Lead Shot.

Using the same amount of charge a lighter projectile will travel further as it will have a higher velocity - less of the energy goes into getting the projectile moving. However the lighter projectile will have less kinetic energy, since kinetic energy is influenced more by mass than by velocity.

You can see this with modern handgun rounds, with larger rounds having lower muzzle velocities* but much greater hitting power.

(*A .45 caliber round is typically around 800-1000 fps while a comparable 9mm round is usually in the 1200-1500 fps range)

They DID know what density was, although they might not have called it that. It was important for them to know if something said to be gold was gold, and not gold mixed with something else - and had been for millennia. As such they understood that different materials had different weights per given volume - so basically density.
In terms of gunnery and shot they probably didn't understand or know of the maths and science behind it. But they would have quickly noticed that heavier shot did more damage at shorter ranges - that is that lead shot did more damage than iron or stone.

Shot for cannon would not have been prepared just prior to a battle - as in a day or two before. Shot would have been ordered and made prior to a campaign and carried along with the rest of an armies stores and powder. (Much like arrows it wasn't that you couldn't make the projectiles in the field, rather that it was better not to rely on doing so as you would probably only have a day to prepare for a battle and the men would be much better employed preparing defenses and setting up their positions (in the case of artillery and/or archers who had to be concerned about protecting themselves from cavalry, against which they effectively had no ability to fight at close range)). Shot would have been made during sieges sure, but that would have been to maintain existing stockpiles at a reasonable level rather than replacing or creating a stockpile from scratch.

Rate of fire for such early cannon is open to debate. As I mentioned earlier these early cannon tended to be breach-loaders with a breach designed to be removed and loaded away from the gun - which was probably safer for the crew as well. Such designs could give a very high rate of fire even compared to later cannon, hampered by the fact that the breach was secured by hammering wooden wedges behind it. I'd estimate that you could probably get a maximum rate of fire of around a shot a minute with a good gun crew...at least as long as you had pre-loaded breaches available. Once you'd gone through them the rate of fire probably dropped to one shot every five minutes or so, maybe more if the powder was being stored some distance from the gun or you were trying to reload for several guns at once. An educated guess would be that the tactics were to fire the guns at a low rate of fire initially, probably a rate at which reloading could keep pace, to scare and harass the enemy. They would probably switch to rapid fire as an enemy reached medium range, in the hopes of disrupting their formations prior to close combat. Then either move to a much lower rate of fire against uncommitted enemy forces or leave the gun to join in the melee.

As I said before, the most logical reason was that the workers were adding the stones and pocketing the lead they displaced. Similar practices were well known in this and later periods, and while technically illegal were usually tolerated as long as it wasn't taken to extremes or quality of the finished product suffered as a result.

In the example I gave with dockyard workers being allowed to take wood scraps home (a well established tradition by the 1700's that must have come from a much earlier period). No one was objecting to workers taking home scraps of wood - even if the scraps were of good enough quality to be used for something other than fire wood. What they objected to was when the workers started to include copper bolts in the scraps, since not only was the copper worth a lot of money but the bolts themselves were meant to be used to secure the frame and hulls of ships. Ships where such practices were ignored were often known for producing vessels of questionable quality that were liable to take in alarming amounts of water when at sea, if indeed they didn't fall apart and sink.

'Corruption' was widespread, and indeed tolerated if not expected in all walks of life, as it was often the only way people could make enough money to survive. Even civil servants and Government officials were not paid anything close to a living wage, so had to be 'corrupt' just to eat. There were some limits to what was acceptable, which usually boiled down to not doing anything that was detrimental to the interests of the country. Or if you like bribes only worked if you could offer something of reasonable quality in the amounts required.

Remembering that punching through a man and taking out the one behind as well.....
And even through him to the next one.....


Now there is a Myth that the Mythbusters may like to try, just how many human analogues in a row could one cannonball take out?...

I believe at a certain point in warfare, the changed the way battle lines were drawn up, to try and get away from this through-and-through-and-through action?... anyone know about when?...

Oh yeah, so they did.... senior moment, I forgot that one.