The caisson was a two-wheeled carriage used to transport ammunition. It carried two ammunition chests and a spare wheel. A stock ending in a crescent moon-shaped lunette allowed the caisson to be hooked to a limber, just like any artillery piece. A caisson with its limber thus held three ammunition chests. The limber hauling the gun carriage was equipped with another, for a total of four ammunition chests per team.
When taken into battle, a caisson was always attached to a limber and pulled by a team of four to six horses. The caisson crew was under the direction of a corporal, who reported to the sergeant in charge of the gun to which the caisson was assigned. A fully loaded caisson and limber combination weighed 3,811 pounds. Caissons belonging to the Union were painted olive drab, those of the Confederacy were gray.