【How-to】What caliber was the minie ball

Up through the Mexican-American War, the standard U.S. musket ball was . 640 caliber, with an approximate weight of . 9 oz (Lewis 1960:108, 111). An 1840 U.S. tactics manual (Scott 1840) states buck-and-ball cartridges were standard by this time, and apparently continued in use for at least another 35 years.