US Patent 8978559 Cartridge cases and base inserts therefor

A base insert for a cartridge case comprises a base end having a lip and a groove proximate the lip and having a primer pocket defined in the base end and an insert end having a base wall and a cylindrical wall extending there from, the base wall and cylindrical wall defining a powder fill pocket. The base wall has a flash hole disposed therein and an inner surface facing the powder fill pocket. The cylindrical wall has an inner surface intersecting with the inner surface of the base wall and an outer surface defining the outer circumference of the base insert. The intersection of the inner surface of the base wall and the inner surface of the cylindrical wall is curved or forms an oblique angle, while the outer surface of the insert end is not curved and does not form an oblique angle.