Abstract: A weapon system having a gun barrel and an in bore air regulation system. The gun barrel has a first end and a second end. The gun barrel has a bore formed therein that extends from the first end towards the second end. The bore is adapted to receive a round. The in bore air regulation system is operably attached to the gun barrel so that the in bore air regulation system is in communication with the bore to regulate air pressure in the bore and thereby control the position of the round in the bore.

Abstract: A gun for firing a round of caseless ammunition, a round of such ammunition having a projectile and a modular propellant, the projectile and a modular propellant being disposable for firing in a gun tube, includes an actuatable valve being selectively openable to the gun tube, the valve for drawing a negative pressure in the gun tube, the negative pressure acting to pull the round into contact with a breech face such that when a firing pin is forceably released, the firing pin reliably strikes a primer of the modular propellant, the primer igniting the modular propellant, the ignited propellant forcefully discharging the projectile from the gun tube. A firing pin and valve assembly and a method of operating a gun are further included.

Abstract: A weapon system having a gun barrel and an in bore air regulation system. The gun barrel has a first end and a second end. The gun barrel has a bore formed therein that extends from the first end towards the second end. The bore is adapted to receive a round. The in bore air regulation system is operably attached to the gun barrel so that the in bore air regulation system is in communication with the bore to regulate air pressure in the bore and thereby control the position of the round in the bore.