Patent ID: 7712244

Claim:
An apparatus for propelling a projectile, said apparatus including: a barrel having a first end and a releasably sealed first region, wherein the first region of the barrel includes a space within the barrel substantially bounded by a second end of the barrel, wherein the barrel includes a plurality of apertures along a longitudinal length thereof, said plurality of apertures extending through the barrel from an exterior of the barrel to an interior of the barrel so as to be transverse to a longitudinal axis of the barrel, and wherein all of the plurality of apertures being aligned in a row which is generally parallel with the longitudinal axis of the barrel; a protrusion for selective insertion within any one of the apertures along the longitudinal length of the barrel to selectively adjust a volume of the first region, wherein the protrusion extends radially-inwardly of the barrel in a substantially transverse orientation to an elongate axis of the barrel; one or more seals for sealing a remainder of the apertures into which the protrusion is not selectively inserted along the length of the barrel; a means for controllably feeding a propellant into the releasably sealed first region; and a means of expanding the propellant whereby the expansion of the propellant causes a projectile disposed within the barrel to be propelled outwardly of the barrel via the first end.