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

An M109A6 Paladin fires a gas-propelled round during calibration in Mosul, Iraq. Photo: US Army Spc. Gregory Gieske

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.