Abstract: A spring disc includes a contiguous outer ring including a first plurality of holes and having a contiguous, upwardly curved portion having an outer edge. A middle ring encompasses a second plurality of holes, and a contiguous inner ring, is encompassed by the outer ring and the middle ring. The inner ring surrounds a central aperture sized to accommodate installation onto a cartridge case member, where the outer ring, inner ring and middle ring operate together so as to support the cartridge case by evenly distributing stresses when installed on a cartridge case. A taper angel &thgr; is built into a bottom with a value of about 1° as measured from the bottom extending radially from the center of the inner ring to the outer edge with reference to a plane parallel to an imaginary plane overlaid on the contiguous outer edge.

Abstract: A hollow grain propellant for use in a lightweight training round. The hollow grain propellant incorporates multi-perforation propellant grain geometry. The hollow grain propellant is configured as a propellant grain having a center hole surrounded by uniform perforations. The center hole is larger than any one of the uniform perforations. The placement of the uniform perforations forms webs of equal length. The hollow grain propellant may include seven or more perforations. The perforations are arranged in a single ring around the center hole. The size of the center hole may be controlled to produce a wide range of bulk densities. The number of perforations may be dependant on the size of the center hole. The number of perforations may be controlled to vary with the size of the center hole to provide for a desired bulk density. The large center hole improves flame permeability through a propellant bed by increasing the porosity of the propellent bed and increasing grain diameter.