Staff Writer (Updated: 5/23/2016):
Prior to the age of the "rifled" cannon, the smoothbore cannon ruled the European battlescape. Smoothbore guns were simpler to produce in number yet devastatingly effective, particularly at close ranges. A rifled barrel allowed for more accuracy at range and went on to replace smoothbore gun types although they offered a slower rate-of-fire overall. Nevertheless, the Model 1857 "Napoleon" 12-Pounder was produced in the United States for the US military Army by several foundries and held origins in the French "Canon Obusier de 12" of 1853. Named after Emperor Napoleon III (nephew of famed general Napoleon I), the French weapon saw extensive service with the army of France throughout the Crimean War (1853-1856) and was of 122mm caliber firing a 4.1 kilogram projectile (either basic ball, shell or canister shot) out to 1,400 yards at 1,440 feet per second. The cannon was a complete system - a gun barrel fitted to a special mounting atop a two-wheeled carriage. Transport was principally by horse or pack animal though it could be repositioned by a crew of handlers over short distances as required.
The American Model 1857 "Napoleon" was the primary artillery field gun of the Civil War as both sides utilized the type in number, finding the weapon to be highly reliable and devastatingly effective at all ranges. Union production totaled 1,156 units whilst Confederate production reached 501 units and, in the case of the latter, Confederate forces sought to recover as many captured Union Model 1857 guns as possible due to manufacturing limitations of the South. For the Union Army, the Model 1857 was originally adopted to replace the existing inventory of Model 1841 "6-Pounder" Field Guns though both weapons remained in service for the duration of the war by necessity. Union versions were generally identified by their muzzle "swell" (a tapered shaping) while many Confederate examples were simpler in form, often doing away with the swell to save on material and expedite production. Some Confederate forms even appeared in brass or iron as dictated by need and available resources, though their brittle nature made them prone to bursting at the breech area (requiring use of a reinforcement band). At the Battle of Gettysburg alone, 142 of the available 360 Union cannons were of the Model 1857 Napoleon type.
Bronze was typically utilized in the manufacture of the Model 1857 barrel which incorporated both tin and copper and resulted in a relatively light and mobile artillery piece with the heavy hitting firepower of previous European designs. The bore diameter measured 4.62 inches with a 66-inch overall running length, alone weighing 1,230lbs. This required the use of a heavy-duty wheeled carriage system for local transport. Additionally, a two-wheeled "limber" cart was used to prop the support "legs" up for long-distance travel which, in effect, created a four-wheeled transport system. A "caisson" served to supply the needed ammunition types to the gunnery crew of seven men.
The Model 1857 was cleared to fire several ammunition types depending on the battlefield situation. Projectiles were named after their weight (as in "12-pounder" being a 12-pound cannonball) though this was not always followed explicitly - rifled cannon presented its own set of designation issues, beginning to fall more in line with bore diameters then shot weight.