Field artillery in the American Civil War
Early cannons were identified by the term "pounder" (abbreviated "pdr"). This referred to the weight of the cannonball the gun fired. For example, a 12 pounder fired a round  solid piece of steel. In the 17th century, when howitzers were developed, the term pounder began to be used less and less although it was used through the Civil War. Smooth bores included both guns and howitzers. Both had shorter barrels and used a higher trajectory. Both were less accurate than rifled cannons.