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.
[10] 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.
Along with Rodman guns, some were deployed shortly after the outbreak of the Spanish–American War in 1898 as a stopgap; it was feared the Spanish fleet would bombard the US East Coast.
[11] By summer 1863, Union forces became frustrated by the heavily fortified Confederate position at Fort Sumter, and brought to bear the 10-inch (250 mm) Parrott, along with several smaller cannons.
It was widely believed in the north that a massive 10-inch Parrott would finally break the previously impenetrable walls of the fort, which had become the symbol of stalwart steadfastness for the Confederacy.
In contrast, the 10-inch-bore (250 mm) 300 lb (140 kg) shot, with a muzzle velocity of 1,111 ft/s (339 m/s), strikes the target at the same range still moving at 700 ft/s (210 m/s), due to its much higher mass-to-drag ratio.
In terms of the ability to punch holes in fortifications, at that long range the light 24 lb (11 kg) shell would be expected to only breach a 6-inch-thick (150 mm) brick wall.
In contrast, the greater mass and retained velocity of the 300 lb (140 kg) shell would enable it to penetrate 6 to 7 ft (180 to 210 cm) of brick (given the quality of the material back then).
A famous large 8-inch (200 mm) Parrott cannon, called the Swamp Angel, was used by federal Brigadier General Quincy Adams Gillmore to bombard Charleston, South Carolina.
[14] On August 21, 1863 Gillmore sent Confederate general P. G. T. Beauregard an ultimatum to abandon heavily fortified positions at Morris Island or the city of Charleston would be shelled.
[15] After the war, a damaged Parrott rifle said to be the Swamp Angel was moved to Trenton, New Jersey, where it rests as a memorial today at Cadwalader Park.