These are two excellent examples of the 20-ponder Parrott rifle: their limbers, carriages, barrels and all other things weaponry are in terrific condition. The muzzles have well-defined stamps which made identification very easy. As far as I know, these rifles represent the largest caliber weaponry at Gettysburg. There might be a few larger ordinances but I have not found them yet. The rifles look like the 3-inch ordnance rifles but on steroids. They also have that big, fat, band about the breech which other non-Parrotts do not have, which distinguishes this weapon form all others. The 20-pdr Parrott rifles were among the heaviest guns used @ Gettysburg. The gun tubes alone weighed around 1,700 pounds (this one was 1745), compared to 1,200 pounds for a 12-pounder Napoleon or 900 pounds for a 3-inch Rifled Cannon. However, the 20-pdr could launch a shell to a range of 4400 yards. There is also a Confederate "copy" made by Tredegar Iron Works of the basic Parrott rifle. These guns also incorporated rifling. Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis. This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy. SOURCE
The two rifles and the 5th New York Battery - US Battery Tablet (2) are located inside the Evergreen Cemetery Gatehouse, just south of the wrought iron fence which separates it from the Soldiers' National Cemetery. When entering Evergreen Cemetery, walk down the asphalt road and this is the first thing you will see just past the cemetery lodge, on the right. The monument and rifles faces northwest toward the Gettysburg National Cemetery, presumably in the direction of the approaching danger. Parking is available at metered spots along the side of the Baltimore Pike, the road outside the cemetery. I visited this rifle on Friday, August, 2012 at 2:53 P.M., E.D.T. I was at an elevation of 616 feet, ASL. I used a Canon PowerShot 14.1 Megapixel, SX210 IS digital camera for the photos.
My usual SOURCE for all things weapons at Gettysburg provided me additional information about this weapon which did not appear on the muzzle. I used red to designate that data. The rest is as it appears exactly on the muzzle, starting at the top or just to the left of the 12 o'clock position @ the 11 o'clock position and moving clockwise.
No. 296 ......1864 ......W.P.F. ......3.67 ......R.M.H. ......1745 ......GRVS 5RH ......
Muzzle Stamp Explanation
No. 296 refers to the Army registration number, a way for the military to keep track of the guns when the received a shipment from the various foundries which supported the Union efforts. 1864 refers to the date of manufacture. W.P.F. refers to the foundry, West Point Foundry out of Cold Spring, NY. The foundry is on the National Register of Historic Places. 3.67 is designation of the rifle and refers to the size of the bore in inches. The 20-Pounder designation in the name refers to weight of the projectile. These weapons go by both names. R.M.H. are the initials of the inspector who gave the gun a once over before it was shipped out to the Federal army. Those initials stand for Richard Mason Hill. 1745 refers to the weight of the firing tube, usually a kind of a fingerprint for these things as each one is unique to the rifle. GRVS 5RH, information provided by my source, refers to number of rifling grooves, left or right twist. In this case, 5 right hand twists were made to rifle this cannon. If you were to look at the close-ups of the muzzle stamps, the rifling grooves are easy to discern; they are spirally.
About the Foundry
The West Point Foundry was an early ironworks in Cold Spring, New York that operated from 1817 to 1911. Set up to remedy deficiencies in national armaments production after the War of 1812, it became most famous for its production of Parrott rifles and other munitions during the Civil War, although it also manufactured a variety of iron products for civilian use. The rise of steel making and declining demand for cast iron after the Civil War caused it to gradually sink into bankruptcy and cease operations in the early 20th Century.
In 1835, Captain Robert Parker Parrott, a West Point graduate, was appointed inspector of ordnance from the foundry. The next year, he resigned his commission and on October 31, 1836 was appointed superintendent of the foundry. It prospered under his tenure, and was the site of numerous experiments with artillery and projectiles, culminating in his invention of the Parrott rifle in 1860. During Parott's tenure, in 1843, the foundry also manufactured USS Spencer, a revenue cutter which was the first iron ship built in the U.S. The foundry's operations peaked during the Civil War due to military orders: it had a workforce of 1,400 people and produced 2,000 cannon and three million shells. Parrott also invented an incendiary shell which was used in an 8-inch Parrott rifle (the "Swamp Angel") to bombard Charleston. The importance of the foundry to the war effort can be measured by the fact that President Abraham Lincoln visited and inspected it in June 1862.
SOURCE
About the Inspector
Richard Mason Hill (Died March 25, 1876) entered the United States Military Academy at West Point, New York in July of 1857. He was a member of the 1861 (June) Class, and was ranked 7th in the standing upon graduating. As customary, he was brevetted 2nd lieutenant at this time and was assigned to the Ordnance Department. He was promoted to 1st lieutenant on June 24, 1861, and was brevetted major on March 13, 1865 for "faithful and meritorious service in the Ordnance Department." He remained in the United States military achieving the rank of full major.
About the Gun
These two Federal 20-pdr Parrotts accurately represent Captain Elijah Taft’s 5th New York Light Artillery Battery. This battery was the only Federal battery at Gettysburg that had 20-pounder rifles. His six guns were stationed along a ridge in Evergreen Cemetery near the Taneytown Road and were active in the fighting of July 3rd. The gun was invented by Robert Parker Parrott (1804 - 1877), a West Point graduate. He resigned from the service in 1836 and became the superintendent of the West Point Foundry in Cold Spring, New York. He created the first Parrott Rifle (and corresponding projectile) in 1860 and patented it in 1861. SOURCE
Like its siblings, the 10-pdr and 30-pdr Parrotts, gun-founder Robert Parker Parrott designed the 20-pdr using composite construction. 
By placing a wrought iron band around the breech of a cast iron gun tube, Parrott’s West Point Foundry produced an affordable weapon which reached mass production faster than contemporary rifled guns. Parrott’s process went beyond just sliding a reinforcing band on the gun as other contemporaries had done. His technique involved specific a method to construct the band, affix the band to the tube, and to cool the piece. The entire process is best discussed in a separate post, but for those interested in the details, the patent itself offers ample explanation.
20-pdr production did not start until the summer of 1861. Production continued until the fall of 1864 with over 330 examples delivered for Army or state contracts. West Point Foundry delivered a similar quantity to fill Navy contracts during the course of the war. In terms of construction, the 20-pdr was a scaled down 30-pdr. On the 20-pdr, the characteristic band was 16.5 inches long and 1.5 inches thick (compared to 13 inches by 1.19 inches for the 10-pdr; 19 inches by 2 inches for the 30-pdr). The bore measured 3.67 inches across the flats. That caliber corresponded directly with the 6-pdr field gun then in service. The 20-pdr had five groove increasing pitch rifling, designed to use Parrott’s patent projectiles.
Overall the finished gun tube measured nearly 90 inches long, with weights varying between 1650 and 1800 pounds. On the exterior, the 20-pdr had no muzzle swell. The gun narrowed sharply just in behind the trunnions. This gave the 20-pdr a “swelled” appearance between the trunnions and reinforcing band. Trunnions measured 4.62 inches in diameter and 3.5 inches long. Because of such, the 20-pdr Parrott used a modified 32-pdr Field Howitzer carriage. Dressed out for service, the gun on its carriage with limber weighed in excess of 4400 pounds. This rated the weapon among the heaviest designated for field service, requiring an eight horse team. SOURCE
About the Battery
The Fifth New York Independent Battery of Light Artillery was organized at Brooklyn, N. Y., August 15, 1861. At its organization it was intended that it should form a part of Sickles' Excelsior Brigade. It was mustered into the United States service November 8, 1861, with Captain Elijah D. Taft (1819-1915) as captain, and, leaving Brooklyn on the 16th, was ordered to Washington. Taft was a 38-year old carpenter in the borough of Brooklyn in 1855, according to the New York State Census of that year. At the battle of Gettysburg, Taft had six twenty-pounder Parrotts, or three full sections; and his guns were the only ones in General Meade's entire army on that field which were heavier than the ten-pound rifles or twelve-pound Napoleons used by the other batteries. At this time Captain Taft was in command of the Second Brigade of the Reserve Artillery, Army of the Potomac. At Gettysburg, & under Taft's command, the Brigade brought 146 men to the field (and the aforementioned six 20 lb Parrotts) and among them, two were killed (Private John C. Begg & Private Anton Thalheimer) and two were wounded ( Sergeant Dillon and Private Wittenberg). For some reason the monument only has one soldier as being killed.
The cast-iron tablet marks the position and actions of Taft's US Battery on July 2 & 3, 1863 and reads as follows:
Army of the Potomac
Artillery Reserve
Second Volunteer Brigade
Fifth New York Light Artillery
Six 20 pounder Parrotts
Captain Elijah D. Taft commanding
July 1 Arrived and halted in park at about 10 a.m. Moved to the Evergreen Cemetery at 3.30 p.m. and engaged from 4 p.m. until dark. Two guns posted in the Cemetery firing westwardly. Four south of and facing Baltimore Pike firing on a Confederate battery on Benner's Hill.
July 3 Engaged at intervals in same position until 4 p.m. when relieved by three of the guns on Baltimore Pike.
Casualties of the battery killed 1 man wounded 2 men.