Multi-piece polymer ammunition cartridge

1. A polymeric ammunition having a 2 piece case comprising:

an primer insert comprising a top surface opposite a bottom surface and a substantially cylindrical coupling element that extends from the bottom surface, a primer recess in the top surface that extends toward the bottom surface, a primer flash hole aperture positioned in the primer recess to extend through the bottom surface, and a groove positioned around the primer flash hole aperture in the primer recess;

a polymeric middle body that extends from a body coupling over at least a portion of the primer insert, wherein the polymeric middle body is molded over the cylindrical coupling element and into the primer flash hole aperture and into the groove to form a primer flash hole;

a polymer nose comprising

a generally cylindrical neck having a projectile aperture at a first end;

a shoulder comprising a shoulder top connected to the generally cylindrical neck opposite a shoulder bottom; a side wall extending from the shoulder;

a groove positioned around the side wall;

a skirt connected circumferentially about the groove to extend away from the groove and terminates at a point, wherein the groove and the skirt are adapted to mate to a polymer cartridge, wherein the groove and the skirt are adapted to mate to the body coupling to couple the polymer nose to the polymeric middle body to form a polymer ammunition cartridge;

a diffuser comprising a diffuser aperture positioned in the primer recess to align the diffuser aperture with the primer flash hole;

a primer inserted into the primer recess;

a propellant at least partially filling the propellant chamber; and

a bullet frictionally fitted in the bullet-end aperture.

2. The polymer ammunition of claim 1 , wherein the groove and the skirt form a half lap junction with the skirt on the inside of the polymer nose.

3. The polymer ammunition of claim 1 , wherein an angle formed between the groove and the skirt is between 40 and 140 degrees.

4. The polymer ammunition of claim 1 , wherein the angle is about 90 degrees.

5. The polymer ammunition of claim 1 , wherein the angle is greater than 90 degrees.

6. The polymer ammunition of claim 1 , wherein the angle is less than 90 degrees.

7. The polymer ammunition of claim 1 , wherein the shoulder comprises an outer shoulder surface having an outer angle opposite an inner shoulder surface having an inner angle and a skirt surface adjacent to the inner shoulder surface.

8. The polymer ammunition of claim 7 , wherein the outer angle is the same as the inner angle.

9. The polymer ammunition of claim 1 , wherein the polymer nose, the polymeric middle body or both individually comprise a nylon polymer, polycarbonate polymer, polybutylene polymer or a mixture thereof.

10. The polymer ammunition of claim 1 , wherein the polymer nose, the polymeric middle body or both individually comprise a fiber-reinforced polymeric composite.

11. The polymer ammunition of claim 1 , wherein the polymer nose, the polymeric middle body or both individually comprise between about 10 and about 70 wt % glass fiber fillers, mineral fillers, or mixtures thereof.

12. The polymer ammunition of claim 1 , wherein an adhesive groove is positioned in the projectile aperture.

13. The polymer ammunition of claim 1 , wherein the polymer nose, the polymeric middle body or both individually comprise a polymers selected from the group consisting of polyurethane prepolymer, cellulose, fluoro-polymer, ethylene inter-polymer alloy elastomer, ethylene vinyl acetate, nylon, polyether imide, polyester elastomer, polyester sulfone, polyphenyl amide, polypropylene, polyvinylidene fluoride or thermoset polyurea elastomer, acrylics, homopolymers, acetates, copolymers, acrylonitrile-butadinen-styrene, thermoplastic fluoro polymers, inomers, polyamides, polyamide-imides, polyacrylates, polyatherketones, polyaryl-sulfones, polybenzimidazoles, polycarbonates, polybutylene, terephthalates, polyether imides, polyether sulfones, thermoplastic polyimides, thermoplastic polyurethanes, polyphenylene sulfides, polyethylene, polypropylene, polysulfones, polyvinylchlorides, styrene acrylonitriles, polystyrenes, polyphenylene, ether blends, styrene maleic anhydrides, polycarbonates, allyls, aminos, cyanates, epoxies, phenolics, unsaturated polyesters, bismaleimides, polyurethanes, silicones, vinylesters, urethane hybrids, polyphenylsulfones, copolymers of polyphenylsulfones with polyethersulfones or polysulfones, copolymers of poly-phenylsulfones with siloxanes, blends of polyphenylsulfones with polysiloxanes, poly(etherimide-siloxane) copolymers, blends of polyetherimides and polysiloxanes, and blends of polyetherimides and poly(etherimide-siloxane) copolymers.