i remeber reading once that american frontiers men made a habit of pouring a shot of 'powder' into a slip of paper, so that they could bite/tear the package open, pour a 'measured load' of black powder, drop in a 'bullet'(shot) and then fire.. (being able to reload fast was important when dealing with a wounded deer, or an attacking bear!)

these pre-measured doses of powder were quicker than the then common way of pouring the powder from a horn.. and quickly became the standard way of 'loading' a gun. from there, evolved the cartridge-- powder and shot all in one neat package, to drop down the barrel of gun/rifle, so you could reload even faster.--(a british innovation, i think)

some restoration villiages nowdays make 'cartridges' out of aluminum foil, (no bullet/shot, just powder)--its easier to get the size right-- the 'cartidge' goes down the barrel, and the gun goes 'boom' --homemade blanks for antiques style guns.