During the siege of Fort Sumter in the last half of the Civil War, the United States Army and Navy turned to the use of large Parrott rifles in an attempt to destroy the fort. These new artillery pieces included several important technical innovations, and following the war, the army used Parrott rifles to re-arm Fort Sumter, where they can be seen today.
An almost 19-month siege from August of 1863 to February of 1865 by the US Army and Navy severely damaged Fort Sumter and, except for three guns on the first tier of the right face opposite Sullivan’s Island, significantly reduced its ability to function in harbor defense. Following the Civil War the US Army Corp of Engineers was charged with developing a plan to restore some of its capability. Of the five faces of the pentagon-shaped fort, the right face because of its relationship to Fort Moultrie about 1 mile away was considered the most important.
The Confederate’s judicious use of sandbags as protection against rifled artillery had been an important lesson of the Civil War and the plan the army came up with was to use the perimeter structure as a sand box, rebuild or repair the first-tier casemates on the right face and left flank facing Charleston, enclosing the rear of the casemates with curved brick walls to allow them to be buried in protective sand. A new entrance was provided on the middle of the left flank which is still in use today. The right flank wall facing the Atlantic was rebuilt to about 13 feet above the foundation and the remaining walls cut down to the tops of the first tier.
The choice of armament for the restored fort presented a dilemma. Particularly in the Charleston theater, the rifling of seacoast artillery had proven superior in accuracy and range to the older smoothbore variants. However, the higher charges and prolonged use of the cast iron rifles had demonstrated a preponderance toward failure not seen before in cast iron smoothbores of the Rodman design. The answer for Fort Sumter was a compromise – some of each. They would rearm the right face with repurposed 6.4-inch caliber Parrott Rifles and procure two massive new 15-inch Rodman guns. As the Rodmans were far too large to install in casemates, they would be mounted on top of the reinforced vaults of the left face casemates. A pair of 8-inch Parrotts were to be mounted on the top of the right face and another pair of 8-inch Parrott rifles were mounted on top of the right flank which was rebuilt to about half of its present height. A battery of four 13-inch mortars was emplaced in the parade of the redesigned fort.
The Parrott rifles of the right face casemates were a formidable battery for their day. Although the restrictive embrasure opening limited the extreme range these weapons were capable of, they were more than adequate to cover the one-mile gap between the fort and Sullivan’s Island.
Robert Parker Parrott was a leading designer of artillery in the Civil War. From the West Point Foundry at Cold Springs New York opposite the United States Military Academy on the Hudson River, he produced an array of rifles that ranged from 2.9-inch field pieces to massive 300-pdr. seacoast rifles. His rifles traveled with armies, besieged forts and towns, and armed the new ironclads, cruisers, and blockaders of the US Navy. Copies and captured pieces found their way into the Confederate arsenals. Working on the concept as early as 1860, he patented his reinforcing technique in 1861. As many as 500 of the smaller field pieces were produced during the war.
In producing the 6.4-inch rifle, Parrott machined nine roughly 1 inch wide spiraling grooves into the barrel The right hand twist of the grooves is fairly gentle and increases toward the muzzle. The projectiles for this cannon incorporated a brass band that expanded into the grooves during firing causing the projectile to track along the grooves as it moves down the barrel. Although it does not complete a full revolution in the barrel, the projectile exits the barrel spinning at about 5000 revolutions per minute.
Rifling not only means the projectile stays in the barrel longer exiting on a spiral path but also means the projectile’s weight increases significantly. The elongated bullet-shaped rifle projectile can be two to three times the weight of a ball of the same diameter and the increased mass requires more gunpowder to generate the pressures needed to accelerate the greater mass. The combination of time and pressure puts more stress on the bore of the cannon than cast iron can endure. As the inexpensive metal begins to yield, cracks form on the interior which propagate through the metal after each successive shot until the cannon fails, often with disastrous consequences for the gun crew. During firing, pressures are greatest at the rear or breech of the cannon then drop rapidly as the projectile travels down the muzzle. Cannon designers like Robert Parrott seized on the idea of reinforcing the breech of the rifled cannon. The physics of the over pressure failure mechanism requires that a stronger reinforcing metal be used than that used to mold the cannon. In other words, adding more cast iron would slow but not stop cracks from propagating.
The most common reinforcing metal during the Civil War was wrought iron. The simplest form of wrought iron reinforcement was to form a cylinder of wrought iron, heat it to cause thermal expansion, slip it over the beech and allow it to cool in place. Sometimes two or three cylinders would be placed successively, giving rise to the term double or triple-banded rifles. Robert Parrott felt cylindrical banding was inferior to wrapping and forging a continuous length of wrought iron around the breech while the cannon barrel was being turned. Although the Parrott band gives the appearance of a single reinforcing piece, it is actually a spiral band of metal. For the 6.4 inch-Parrott rifles at Fort Sumter, the banding began as a 60-foot long bar of wrought iron. According to his patent, Robert felt that wrapping was superior to cylindrical banding because the wrapping could accommodate to any irregularities in the breech diameter.
Another innovation from Robert Parrott was integrating brakes into his gun carriage. Traditionally, designers relied on the weight of the cannon to reduce the recoil produced by firing. While effective, it made heavy cannons more costly and difficult to move. The Parrott carriages at Fort Sumter are representative of the superior manufacturing capability of the North during the war and reflect a number of Parrott’s innovations. In addition to the brakes, the top carriage holding the cannon barrel was equipped with adjustable wheels to assist in rolling the cannon into its firing position.
In a casemate-mounted cannon, this meant moving the cannon forward enough to push the muzzle through the embrasure so that the shock wave from releasing the gas pressure as the projectile leaves the barrel moves away from the casemate instead of reverberating within the confined space, likely injuring the hearing of the gun crew.
Parrott incorporated a mechanism whereby turning the eccentric axle of the wheels 90 degrees, alternately lowered the wheels to roll the gun into battery and raised them once ready to fire. The sliding friction of the top carriage on the bottom carriage and the included brake mechanism would stop the recoiling cannon before it dismounted.
Though not an invention of Robert Parrott, the bottom carriages were equipped with wheels that rolled on tracks called traverse rails. There are forward and rear rails mounted to 19-inch-thick granite blocks set in the casemate floor on which the wheels operated. These wheels allow the gun to be trained or aimed to right and left of center. Many visitors note the indentations in the casemate walls near the bottom of the embrasures on both sides. They have the appearance of small fireplaces but are actually designed to receive the front carriage wheels at extremes of angles. They are a feature common to many forts of Fort Sumter’s generation and reflect the front wheel orientation of the standardized casemate gun carriage.
Left: Carriage tongue and Reaction Blocks at Fort Sumter Right: Carriage Tongue Retaining Pin (Russell Horres)
Another feature common to casemates of this period are slots under the embrasure to receive a metal tongue on the front of the bottom carriage. The tongue is held in place by a vertical 3-inch diameter iron pin that is anchored to heavy granite blocks embedded in the embrasure and passes through a hole at the end of the iron tongue. These blocks are known as reaction blocks and serve to prevent the carriage from pulling away from the wall during firing while allowing the carriage to pivot on the pin to traverse the piece left and right. The term reaction block comes from Newton’s Third Law of Motion—“For every action there is an equal and opposite reaction.”
In the 1870 design, the rear openings of the right-face casemates and one left-face casemate adjacent to the salient (point of the pentagon) were sealed off by outwardly curved retaining walls, an additional layer of bricks added to the top of the casemate and the entire interior face buried in sand. Near the stairs leading from the Parrott battery to the top of the right flank, the National Park service has left one of the walls partially in place to illustrate how the entire face was protected. This same modification was made to the casemates of the left flank, where a new entrance that is in use today was created by replacing the embrasure on the central casemate with a doorway. The new door is similar but not identical to the original entrance through the gorge wall. Access to the buried casemates containing the Parrott rifles and service magazines, was via concrete-lined tunnels from the parade.
Advancing technology in artillery design, in particular the ready availability of steel and the employment of breech loading mechanisms, made Fort Sumter’s Parrott rifles obsolete and in the 1898 plans to build Battery Isaac Huger with two powerful 12-inch breech loading rifles it was decided to abandon the Parrott battery in place, filling the casemates with sand through openings cut the top of the vaults and bricking up the embrasures. The sand provided additional protection for Battery Huger from incoming artillery. From around 1900 to 1959 when the Park Service excavated about half of the fort, the right face was sealed off from the world and the buried guns forgotten.
Imagine the excitement when the contractor discovered Civil War relics in the casemates. The four casemates on the east end of the right face were found to be free of sand and those Parrott Rifles were in remarkably good condition, intact except for the brass elevation adjusting screws which were likely salvaged before abandoning the guns. Fort Sumter is the only place you can see a complete battery of 6.4-inch Civil War Parrott rifles on their original carriages.
Preserving these priceless relics has been a priority of the National Park Service. This is no easy task in the salt air and humidity of Charleston and the not infrequent inundation of the fort by tropical storms and hurricanes. Through the Adopt-A-Cannon Program, the Fort Sumter-Fort Moultrie Historical Trust (now the Friends of the Charleston National Parks) raised funds necessary to complete the conservation of the Park's historic cannons. Clemson University’s Warren Lasch Laboratory has been contracted to clean and coat the Parrott rifles with a state-of-the-art corrosion barrier. This work has been in progress for almost a decade and should be completed in 2025. No visit to Fort Sumter would be complete without touring the Parrott battery.
For more interesting details on Fort Sumter’s Parrott Rifles see:
Artillery and Ammunition of The Civil War By Warren Ripley - 1973
The Historic Guns of Fort Sumter and Fort Moultrie by Mike Ryan - 1997
