A barrel assembly for a device for shooting projectiles is disclosed. The barrel assembly comprises a firing chamber with first and second openings, wherein the firing chamber is capable of holding at least two projectiles. A first projectile retention device is located at the second opening of the firing chamber. A propellant injection device injects propellant into the firing chamber through a third opening. A firing control device initiates the injection of propellant into the firing chamber, wherein at least one projectile and the projectile retention device substantially seal the second opening of the firing chamber when propellant is introduced and at least one projectile is expelled out of a barrel through the first opening of the firing chamber.