Dynamite gun

A small model for field use by land forces employed a powder charge to drive a piston down a cylinder, compressing air that was then fed into the gun barrel.

This field model was famously used by Theodore Roosevelt's Rough Riders during the Spanish–American War, but had actually been used previously by Cuban insurgents against Spanish forces.

The original invention of a gun to fire an explosive charge with compressed air was the work of D. M. Medford of Chicago, Illinois.

The USS Vesuvius, launched in 1888, was armed with three fifteen-inch pneumatic guns capable of firing an explosive projectile 1.5 miles (2.4 km), and eventually bombarded Cuba in the Spanish–American War.

From 1894 to 1901, the Army purchased and installed several coastal artillery batteries of 15 inch (381 mm) dynamite guns as part of the coast defense modernization program initiated by the Endicott Board.

A bolt circle for a 15-inch dynamite gun remains near the southwest tip of Fisher's Island, New York on the former site of Fort H. G. Wright.

Pneumatic guns for shipboard use, or at fixed coastal fortifications, could rely on a steam-driven gas compressor as an air source.

When fired, the expanding gas from the smokeless powder compressed the air in the cylinder, which was then fed into the gun barrel, accelerating the explosive projectile.