
The 12-pounder field gun was developed in France in the 1850s and was named for Emperor Napoleon III. At Gettysburg, it made up 39% (142/360) of the total Federal field pieces. The U.S.A. version of the 12-pdr. is distinguished from the C.S.A. version by the muzzle swell, the Confederate tube being straight. The Napoleon fired solid shot, shell, spherical case, and cannister. In overall effectiveness it had no peer.
Bore Diameter 4.62 in (11.73 cm) Tube Material Bronze Tube Length 66 in (168 cm) Tube Weight 1,227 lb (557 kg) Powder Charge 2.5 lb (1.13 kg) Range (5° Elevation) 1,619 yd (1480 m) At Gettysburg 142
http://einstein.human.cornell.edu/ACW/arty/12napusa.html