This in an example of a typical musket cartridge that would include the black powder and lead musket ball. A soldier would tear off the end with their teeth, then pour the cartridge down the barrel of their musket, using their ram rod to push it down. For source and more details, click here.
Image from: http://www.nps.gov/history/museum/exhibits/revwar/image_gal/vafoimg/frameshell.html