Thanks quigley but that wasn't exactly what I was looking for. I stumbled across this article and it answers my question pretty well - I think:
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Black powder is composed of charcoal, sulfur and potassium nitrate. It burns rapidly at a linear rate regardless of the pressure but produces less maximum pressure than does modern smokless powder. and, yes, it does produce clouds of smoke when it is used as a gun powder.
Smokeless powder is composed of two basic materials. One is nitrocellulose and the other is nitroglycerine. Some smokeless powders are made of only one of these materials and is called a single base powder. Others are composed of a mixture of both components and are called double based powders. The reasosn for using mixtures of the two components is to control their burning rates. Faster burning powders are used for shotguns and handguns. The slower burning powders are used for rifle powders.
Smokeless powders are all progressive burning powders. That means that as the pressure within the cartridge increases, so does the burning rate. It produces a more gentle acceleration than does black powder and achieved much greater final pressures and higher total velocities than will blackpowder. Blackpowder burns at the same rate regardless of the increasing pressure. The maximum pressure is reached more quickly but is significalntly less than smokeless powder. These lower total pressures of black powder are the reason that you cannot use smokeless powder in a gun designed for black powder. You will blow it up and yourself along with it.
As for the comparative cleanleness of the two types of powder, black powder leaves MUCH more residue than does smokeless powder. In addition, when the sulfur and potassium nitrate burn they form sulfuric acid and nitric acid which are very corrosive to metal. Black powder residue must be completely removed from your gun as soon as you are through shooting for the day to keep the gun from rusting away. Smokeless powdeer does not have this problem and immediate cleaning is not an issue as long as you don't have any old or foreign cartridges with smokeless powder but a corrosive primer. If you have a cartridge with a corrosive primer, you have to clean immediately.
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