A system for feeding and firing ammunition of the variety having no casing. Sealing of the firing chamber is accomplished by providing a reciprocating bolt assembly having a bolt projection which is telescopingly received in the barrel bore. The projection picks up and seats the projectile in the firing chamber. The propellant charge may be secured to the projectile, or may be separately loaded in the bolt mechanism. In the latter case, a fluid passage extends from the propellant chamber through the bolt projection to the projectile chamber.