Both the Union and Confederate artillery forces used several types of rifled field artillery in the Civil War. One of the more common rifled field guns was the 3 inch Parrot Rifle, named after its inventor, Robert Parker Parrott.
There were actually two types of 3 inch Parrott guns. The original models, first manufactured in 1860, were 2.9 caliber. Other artillery manufacturers were machining their similar sized rifled gun tubes as 3.0 caliber. The size difference was small, but that tenth of an inch was significant, and it was potentially easy to put the wrong size shell in a gun and damaging it when it was fired. In 1863, the Federal government eliminated the 2.9 caliber gun tubes and set the standard at 3.0. The 2.9 tubes were either replaced or machined to the new 3.0 inch standard. The photo at left shows some of the 2.9 caliber guns of Battery B, 1st New York Light Artillery during the Peninsula Campaign in 1862.
The Parrott gun tubes were made of cast iron, and had a distinctive wrought iron reinforcing band on the breech. Even with that reinforcing band, Parrott gun tubes would occasionally burst. Rifling–spiral grooves in the gun tube–produced increased accuracy compared to smoothbore weapons. A brass (or less often some other metal) ring attached to the rear of the shell expanded and engaged the rifling grooves in the gun tube. A one pound charge of gunpowder could fire a 3.0 caliber shell weighing 9 1/2 pounds about 1900 yards at a 5 degree elevation.
Today, 3 inch Parrot Rifles can be seen at several National Battlefields or Military Parks, including Gettysburg, Antietam, Stones River, and these pictured below that I photographed at Kennesaw Mountain.
Arms and Equipment of the Civil War
by Jack Coggins