The gun was invented by Captain
Robert Parker Parrott,
Daniel Treadwell, who developed a method for making
built-up guns in the early 1840s, claimed that Parrott's patent infringed on Treadwell's earlier one, but in 1866
United States District Court court dismissed the case, deciding that Treadwell's claim was invalidated by a 1843 British patent to John Frith. Parrotts were manufactured with a combination of
cast and
wrought iron. The cast iron made for an accurate gun, but was brittle enough to suffer fractures. Hence, a large wrought iron reinforcing band was overlaid on the breech to give it additional strength. There were earlier
cannons designed this way, but the method of securing this band was the innovation that allowed the Parrott to overcome the deficiencies of these earlier models. It was applied to the gun red-hot and then the gun was turned while water was poured down the muzzle, allowing the band to attach uniformly. By the end of the Civil War, both sides were using this type of gun extensively. Parrott rifles were manufactured in different sizes, from the
10-pounder up to the rare 300-pounder. The
20-pounder was the largest field gun used during the war, with the barrel alone weighing over . Both the 10- and 20-pounders were used by both armies. The smaller size was much more prevalent; it came in two bore sizes: and .
Confederate forces used both bore sizes during the war, which added to the complication of supplying the appropriate ammunition to its batteries. Until 1864,
Union batteries used only the . The M1863, with a
bore, had firing characteristics similar to the earlier model; it can be recognized by its straight barrel, without muzzle-swell. Its range was up to with a trained crew. On June 23–24, 1862, President
Abraham Lincoln made an unannounced visit to West Point, where he consulted with retired Gen.
Winfield Scott regarding the handling of the Civil War and the staffing of the
War Department. Following this meeting, President Lincoln visited the West Point Foundry at which the 100- and 200-pounder Parrott cannons were successfully demonstrated in live firing. Naval versions of the 20-, 30-, 60-, and 100-pounder Parrotts were also used by the Union navy. The 100-pound naval Parrott could achieve a range of 6,900 yards (6,300 meters) at an elevation of 25 degrees, or fire an shell 7,810 yards (7,140 m) at 30 degrees elevation. At the end of 1862,
Henry J. Hunt attempted to get the Parrott eliminated from the
Army of the Potomac's inventory, preferring the
3-inch ordnance rifle. When the Parrott gun burst in battle, gunners would chip out the jagged parts and continue firing. In 1889,
The New York Times called on the Ordnance Bureau of the War Department to discontinue use of the Parrott gun altogether, following a series of mishaps at the
West Point training grounds. ==The 300-pound solution==