Whitworth's Original Breechloading Cannon 

The vent hole is on the center of the breech block, so a copper priming tube with a pull cord would be inserted in the rear, and would detonate the powder charge in the gun when the cord was yanked quickly

Spanish Fort Al. 1865 Huzzzaah

Spanish Fort 1865

I grew up in Gettysburg, many years ago and did much original research on these guns...during the Battle of Gettysburg on the second day the Whitworth guns were firing from a position on Seminary Ridge, about 1,000 yards from the Union positions on Cemetary Ridge. After taking some casualties, the guns were moved on the third day to Oak Ridge, near the present Peace Light, where they are located today. From the Oak Ridge location they fired on Union positions, about 3 miles away. The projectiles were said to make a screeching noise. When closing the breech a copper disk was used as a seal at the rear to the barrel...during the Battle of Gettysburg the Alabama artillery unit was out of disks and the guns were muzzle-loaded. Building these barrels was interesting - a long length of 1" X 1" square steel bar was heated, coiled around a mandrel, then forge welded into a short section of barrel. Five short sections were then forge welded into the finished barrel shape, then turned to final shape on a lathe. The projectiles were machined on machinery at the Tredgar Works (??) in Richmond (??). The Union Army had several Whitworth cannons (6?) which were located near the Chain Bridge in the Washington, DC, defenses, but never did engage in any combat. My original high school term paper, written in 1961, might still be on file under "Whitworth, the Man and the Gun", somewhere in the archives at Gettysburg.

Top secret.