A firearm is disclosed for firing caseless ammunition. The firearm fires projectiles by ignition of a separate propellant cartridge disposed therebehind, the projectile carrying a primer charge for igniting the propellant cartridge. The firearm comprises a body including a receiver, a barrel connected to the receiver, and a firing chamber communicating with a bore of the barrel. A mechanism is provided for feeding a projectile and a propellant cartridge therebehind into the receiver. A bolt is slidably mounted in the body and includes laterally open pockets for receiving the fed projectile and cartridge and for advancing them to an armed position within the firing chamber. A portion of the bolt is arranged to ignite the primer charge when the projectile reaches the armed position. The primer charge is disposed within a metal casing, the latter being mounted by friction fit within a recess of the projectile. A sleeve formed of anti-friction material surrounds the primer casing to facilitate insertion of the primer casing into the recess. The primer casing may contain a slower burning tracer material disposed ahead of the primer charge and to be ignited thereby.