These are 9-pellet .310″ buckshot cartridges, based on surviving examples of American Civil War provenance. Interestingly, we know that Columbus Arsenal was producing these for issue as late as 1863! They will fit your .69 caliber muskets, and your 12ga muzzle loaders (same bore diameter). When I shoot them myself, I load them with 110gr of 1Fg Black Powder. Make sure you use a load that is safe for you, and for your weapon.