Cartridge with elastic pusher cup

In an improved 40 mm ammunition cartridge comprising:

• a case including a bore, said bore having an interior surface provided with a groove,
• a tubular cup seal disposed in said bore, said cup seal having an outer tubular section and an inner tubular section connected by a single annular fold section circumscribing an area, said inner tubular section having a sidewall and a closed end,
• said outer tubular section having an open end including an exterior annular flange disposed in said annular groove, said closed end increasing in thickness towards the center at an angle of about 7.degree. from the juncture with said sidewall,
• means for locking said flange in said groove to anchor and seal said cup in said bore;
• a 40 mm projectile inserted in said circumscribed area of said annular fold, and
• propellant gas generating composition disposed adjacent said open end of said cup seal,
• said cup seal being made of elastic material capable of expanding without rupture to contain the generated gas, and of contracting on reduction in volume of said gases on cooling for removal from a gun after firing said propellant composition.