Heated shot or hot shot is round shot that is heated before firing from muzzle-loading cannons, for the purpose of setting fire to enemy warships, buildings, or equipment. The use of heated shot dates back centuries. It was a powerful weapon against wooden warships, where fire was always a hazard. It was rendered obsolete in the mid-19th century when vessels armored with iron replaced wooden warships in the world's navies. Also at around the same time, the replacement of solid-iron shot with exploding shells gave artillery a far more destructive projectile that could be fired immediately without preparation.
Mobile furnace, operated by the Royal Norwegian Navy, used to heat cannon shots (ca. 1860).
A contemporary aquatint of the 1782 Franco-Spanish attack on Gibraltar. A Spanish Floating battery is shown exploding after the British defenders set it on fire with heated shot
An iron grate for heating iron shot during the Great Siege of Gibraltar (1779–83)
The Heated-shot furnace at Fort-la-Latte, showing its proximity to the ramparts where the fort's guns were placed
A round shot is a solid spherical projectile without explosive charge, launched from a gun. Its diameter is slightly less than the bore of the barrel from which it is shot. A round shot fired from a large-caliber gun is also called a cannonball.
Various types of round shot made from stone, iron and lead found on board the 16th-century carrack Mary Rose
Mons Meg with its 20-inch caliber (51 cm), 386 lb (175 kg) cannonballs
Cannonball equipped with winglets for rifled cannons, c. 1860
