Low velocity cartridge having total propellant ignition

Claim 1

An ammunition round comprising a case having a stepped bore of two different diameters and a base, said base including means for receiving a primer centrally thereof, the bore of lesser diameter being disposed adjacent to said base and in communication with said primer receiving means, the bore of larger diameter being disposed coaxial with said lesser diameter bore and remote from said base, the relative diameters of said bores being dimensioned such that said lesser diameter bore defines a chamber of significantly smaller volume than the chamber defined by said larger diameter bore whereby said lesser diameter bore defines a higher pressure chamber relative to the chamber defined by said larger diameter bore, propellant means disposed in said lesser diameter bore adjacent to said base, a projectile axially disposed in said larger diameter bore to extend thereinto toward said lesser diameter bore, and sabot means disposed within said lesser diameter bore and in contact with said projectile for propelling said projectile axially from said case, said sabot means being dimensioned axially to prevent expansion of gasses produced by said propellant into said larger diameter bore in response to predetermined axial movement of said projectile from said case.