Explosive shells were first used with bombards, extreme-caliber bomb tossing guns with very short barrels and highly inaccurate. These were siege weapons only. With the advent of dynamite explosive ammunition became commonplace in cannon, and further development has made explosive shells smaller and smaller. At the Steam level, only cannon shells can be armor-piercing, at Nuclear support weapons can be armor-piercing, at Fusion weapons with a base damage value of 12 or higher can use it, and at later tech levels, all projectile weapons can use such ammunition.
Also known as anti-personnel rounds, Explosive rounds always have an Area Effect, with a diameter equal to the damage value of the attack.
Against large, soft targets, like a wooden ship or an earthen wall, explosive ammunition can be particularly devastating. Double the base damage of the weapon in such cases. The GM decides which targets are soft targets, but it never applies to any metal-armored construction.