James rifle

Early in the war there were many 6-pounder (2.72 kg) bronze smoothbore guns in service with the field artillery and few rifled pieces available.

The initial type was created by reaming existing 6-pounder (2.72 kg) Model 1841 guns to 3.8 in (97 mm), then rifling them.

"[7] In the early part of the Civil War the Union army lacked heavy rifled siege artillery.

To fill this gap, the army rifled existing heavy smoothbore pieces with the system developed by Charles T. James.

Several 14-pounder James rifles at the Manassas National Battlefield Park in Virginia commemorate the Providence Marine Corps of Artillery, which served in the First Battle of Bull Run as the First Rhode Island Battery with this type of weapon.

A 14-pounder (6.35 kg) (3.8 in (97 mm)) James rifle on the First Bull Run battlefield, the only weapon entirely designed by James adopted by the US Army.
Two Model 1829 32-pounder (14.5 kg) seacoast guns, rifled by the James method (sometimes called 64-pdr (29 kg) James rifles). The one in the foreground is on a siege carriage. The one behind is on an iron, front pintle, barbette carriage.
A James pattern solid shot. The “birdcage” at the base would have been covered by sheet lead which, upon firing the gun, would have expanded into the grooves of the rifling.