Extended charge cartridge assembly

A cartridge assembly for propelling a projectile assembly through a gun tube, said assembly comprising:

• a tubular case having a primer in one end and having an2opposite open end, said projectile assembly extending into and out of said case through said open end;
• said projectile assembly including a subcaliber elongated penetrator and a sabot encircling and gripping said penetrator, said sabot having a front bourrelet outside of said case providing a pressure barrier between said penetrator and said gun tube and an aft bourrelet having a plurality of spaced outwardly extending portions spaced rearwardly from said front bourrelet providing circumferentially spaced lateral support to a portion of said penetrator, and a tubular combustible case extension having one end attached to said open end of said case, said case extension extending beyond said case between said bourrelets to form a toroidal cavity therebetween about said sabot;
• a propellant charge in said case and in said toroidal cavity;
• and
• an ignition assembly supported within said case extending from said primer through said propellant charge and into said toroidal cavity so as to ignite said propellant in said toroidal cavity substantially concurrently with said propellant in said case.