Whitworth's Original Breechloading Cannon

Although the Whitworth gun doesn't look that big, it was apparently capable of doing more damage at greater ranges than muzzleloading rifled cannon of the Civil War era. In the post Civil War negotiations between the U.S. and Great Britain, the Whitworth guns supplied by the Brits to the Confederate Army were named for reparations by the Brits to the U.S. The Brits also had the breechloading Armstrong gun in six and 12-pounder sizes. I've seen them in operation with the Fort Henry Guard in Canada, and a well-trained crew could operate one very quickly. I don't know if Armstrong guns were exported to the Confederacy, but they were apparently standard issue to the British Army's Royal Artillery.

While Breach Loading was a step up, pneumatic recoil was what enabled indirect fire.