High-explosive rounds and metal balls are the cliche options for what to fire out of a howitzer. Discerning cannon users who want to fire less stereotypical munitions should check out these 5 military experiments:
1. Nuclear warheads
There was a time when the American nuclear arsenal was as much about tactical weapons as strategic, and one of the greatest artillery rounds was the M65 which packed a 15 to 20-kiloton nuclear warhead. The U.S. has phased out nuclear artillery rounds, but China, India, and Pakistan still have them.
Artillery-launched drones are a thing, allowing batteries to launch drones in support of special operators and other ground forces.
Right now, the main drone launched from cannons is the Coyote drone. Coyotes are used in the Navy's experimental LOCUST project, a plan to launch "swarms" of up to 30 drones from cannons. The drones would work together to achieve tough missions.
3. Space program experiments
Project HARP was a U.S. and Canadian program to test space re-entry vehicles by firing them from cannons. A HARP cannon at Yuma Proving Grounds, Arizona successfully fired a test vehicle on Nov. 18, 1966, to an altitude of 111 miles, almost 50 miles above the boundary of space. Most of the HARP tests were fired to lower altitudes and carried experimental space parts to see how they acted during descent.
In the late 1970s, the Army experimented with firing artillery rounds that carried cameras that could beam video back to a ground station for the duration of the rounds' parachute-resisted descent. The tests were mostly failures, but the Army still designed a lethal version of the round that carried an explosive canister.
The U.S. military developed the M549, a 155mm artillery shell that featured increased range thanks to a rocket engine housed inside the round. The cannon crew fired the round with normally and, before the round started to drop, the rocket engine would ignite and increase the weapon's range.