projectile the control circuit 204 also controls how much propellant the propellant injection device 207 injects into the firing chamber so as to vary the force at which the projectile is expelled from the firing chamber the user of the gun may vary the amount of propellant by for example turning a dial on the handle 203 or by inputting the command into the control circuit 204 the barrel assembly 201 comprises among other features a firing chamber 208 with a first opening 209 and a second opening 210 a projectile retention device 211 a projectile retention device 212 a storage chamber 213 and a propellant inlet 214 as will be explained in more detail below the operation of the barrel assembly will now be described with reference to fig3 a 3 d fig3 a illustrates the firing chamber 208 being loaded with two projectiles 215 216 it will be understood by those skilled in the art that any number of projectiles can be loaded into the firing chamber 208 the size of the firing chamber 208 can vary and the position of the first and second projectile retention devices 211 212 can also vary to accommodate the desired number of projectiles in the firing.