Cartridge base and plastic cartridge case assembly for ammunition cartridge

1. A cartridge for ammunition comprising:

a base having an axial end section having a primer cavity therein and a radially outwardly extending peripheral extraction lip;

an annular wall extending from said enlarged outer peripheral lip section to an opposite end;

an annular ledge axially positioned at an inner end of said primer cavity and radially extending inwardly from said annular wall;

a passage having a reduced diameter compared to said primer cavity and extending through said annular ledge;

a main charge cavity at an opposite side of said ledge from said primer cavity and within the confines of the annular wall;

a knurl section on an outer surface of said annular wall;

said knurl section having canted grooves thereon; and

a plastic cartridge case having a rear end comprising:

an outer flange extending about said annular wall and engaging said knurl section, and

an inner flange extending about said main charge cavity inside said annular wall and overlay an entirety of said annular ledge only to said passage,

wherein said annular wall is sandwiched between said inner and outer flanges with said knurl section engaging said outer flange, and

wherein said knurled section forms a raised pattern extending outward from said outer surface of said annular wall from 0.004 to 0.010 inches.

2. The cartridge as defined in claim 1 wherein said knurl section axially aligns in part with said annular ledge and fully circumscribes said outer surface of said annular wall.

3. The cartridge as defined in claim 1 wherein said base being made from carbon steel.

4. The cartridge as defined in claim 1 wherein said canted grooves are cross-hatched and form diamond shaped hatchings.

5. The cartridge as defined in claim 1 wherein said knurl section axially aligns in part with a thickened section of said annular wall.

6. The cartridge as defined in claim 1 wherein said knurl section is formed by grooves angled with respect to a longitudinal axis of said cartridge.

7. A method of manufacturing a composite ammunition cartridge comprising:

pressure forming a metallic base with an axial end section having a primer cavity therein and a radially outwardly extending extraction lip;

extending a pressure formed annular wall from said enlarged outer peripheral lip section to an opposite end;

axially positioning an annular ledge pressure formed at an inner end of said primer cavity and radially extending said annular ledge inwardly from said annular wall;

forming a passage with a reduced diameter compared to said primer cavity and extending through said annular ledge;

pressure forming a main charge cavity opposite of said annular ledge from said primer cavity;

knurling a knurl section on an outer surface of said annular wall having grooves pressure formed thereon and extending outward from said outer surface of said annular wall from 0.004 to 0.010 inches; and

molding an outer flange of a cartridge about the periphery of an outer surface of the annular wall and intruding into said knurl section, and

molding an inner flange of said cartridge to extend about said main charge cavity inside said annular wall and overlay an entirety of said annular ledge only to said passage,

wherein said annular wall is sandwiched between said inner and outer flanges.

8. The method as defined in claim 7 further comprising:

said pressure forming being high speed cold forming.

9. The method as defined in claim 7 further comprising:

said metallic base being made from carbon steel.

10. The cartridge as defined in claim 1 wherein said knurl section extends from 0.050 to 0.160 inches above said extraction lip.

11. The cartridge as defined in claim 1 wherein said annular wall comprises a uniform diameter outer surface.

12. The method as defined in claim 7 wherein said knurling step includes extending said knurl section from 0.050 to 0.160 inches above said extraction lip.

13. The method as defined in claim 7 wherein said annular wall comprises a uniform diameter outer surface.