Multi-piece polymer ammunition cartridge

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

a 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 comprising a polymeric body extending from a body coupling over at least a portion of the primer insert, wherein the polymeric 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; and

a nose junction positioned around the shoulder bottom, wherein the nose junction is a nose groove and a skirt connected circumferentially adjacent to the nose groove to extend away from the shoulder bottom to a skirt point, wherein the nose junction and the skirt are adapted to mate to the body coupling to form a flush fit between the skirt point and the polymeric middle body, wherein the nose junction is a half lap junction with the skirt on the inside of the polymer nose;

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 nose of claim 1 , wherein the nose junction is a groove and the skirt is adjacent to the groove on the inside of the polymer nose and is adapted to mate to the body coupling.

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

4. The polymer nose of claim 1 , wherein an angle formed between the nose junction and the skirt is about 90 degrees.

5. The polymer nose of claim 1 , wherein an angle formed between the nose junction and the skirt is greater than 90 degrees.

6. The polymer nose of claim 1 , wherein an angle formed between the nose junction and the skirt is less than 90 degrees.

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

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

11. The polymer nose 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 nose of claim 1 , wherein the projectile aperture further comprises a adhesive groove in the projectile aperture.

13. The polymer nose 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.