The bolter is the iconic sidearm of the Space Marines and one of the most recognisable weapons in the Warhammer 40,000 setting. Rather than firing conventional bullets, it launches self-propelled explosive rounds known as bolts. Each bolt punches through armour or flesh under the momentum of an initial charge, then ignites a rocket motor and detonates a mass-reactive warhead deep inside the target. The result is a devastating internal explosion rather than a simple puncture wound.
Standard bolters are heavy, thick-barrelled firearms, too large and punishing to be wielded effectively by an ordinary human. Their weight, recoil, and thunderous report make them the signature arm of superhuman warriors. Variants abound across the setting: the compact bolt pistol favoured by officers, the two-handed heavy versions mounted on vehicles or carried by elite infantry, and the storm bolter, which pairs twin barrels for a heavier rate of fire.
Other factions field their own patterns of bolt weapon, but the design is most closely tied to the Emperor's superhuman legions, for whom it is both a practical tool and a sacred object. Many bolters are ancient relics, engraved with honours and blessed by tech-priests, passed between warriors across centuries of unending war.