Multi-piece cartridge casing and method of making
A multi-piece ammunition cartridge casing includes a casing base extending along a central axis and defining an opening extending axially into the casing base from the distal base end. The inner casing surface defines a circumferential groove with a groove radius greater than a radius of an adjacent portion of the opening. The cartridge casing also includes a casing body with a proximal end portion disposed in the opening of the casing base. The casing body is secured to the casing base by way of a flange protruding radially outward in mating contact with the circumferential groove.
1. An ammunition cartridge casing comprising:
a casing base of a first metal, the casing base extending along a central axis from a proximal base end to a distal base end, the casing base having a generally cylindrical outer surface with an outer case diameter, and an inner casing surface defining an open region extending axially into the casing base from the distal base end to a distal inner face, wherein the inner casing surface has a shoulder portion extending radially inward and proximally from the distal base end, an axial portion extending proximally from the shoulder portion towards the distal inner face, and a circumferential groove between the distal inner face and the axial portion, wherein the circumferential groove has a groove radius greater than a radius of the axial portion, and wherein the casing base defines a primer pocket between the proximal base end and the distal inner face, the primer pocket in communication with the open region via a flash opening in the distal inner face; and
a casing body of a second metal, the casing body secured to the casing base and having a tubular sleeve portion extending along the central axis from a proximal sleeve end to a distal sleeve end, a proximal body portion connected to the proximal sleeve end and including (i) a sleeve shoulder extending along the shoulder portion of the casing base, (ii) an axial sidewall extending along the axial portion of the casing base, (iii) a flange protruding radially outward from the axial sidewall and mating with the circumferential groove, and (iv) a proximal body wall engaging and extending radially inward along the distal inner face of the casing base, the proximal body wall defining a wall opening around the flash opening.
2. The ammunition cartridge casing of claim 1 further comprising a gasket disposed between the shoulder portion of the casing base and the sleeve shoulder of the casing body, the gasket comprising a non-conducting material.
3. The ammunition cartridge casing of claim 1 , wherein the inner surface of the axial portion of the casing base defines a plurality of facets.
4. The ammunition cartridge of claim 1 , wherein the axial portion of the inner casing surface defines one or more features selected from a flat, a spline, a cusp, a groove, a recess, and a serration.
5. The ammunition cartridge casing of claim 1 , wherein the inner casing surface of the casing base has an increased surface roughness compared to the outer surface.
6. The ammunition cartridge casing of claim 1 , wherein the first metal and the second metal are selected from brass, mild steel, stainless steel, aluminum alloy, titanium, and titanium alloy, and wherein the casing base is compositionally distinct from the casing body.
7. The ammunition cartridge casing of claim 1 , wherein at least one of the first metal and the second metal is aluminum alloy 7075 or aluminum alloy 7068.
8. The ammunition cartridge casing of claim 1 , wherein the cartridge casing has an ultimate tensile strength of at least 70,000 psi.
9. The ammunition cartridge casing of claim 8 , wherein the ultimate tensile strength is at least 100,000 psi.
10. An ammunition cartridge casing comprising:
a casing base extending along a central axis from a casing head to a distal base end, the casing base having a generally cylindrical outer surface with an outer case diameter, and an inner casing surface defining an open region extending axially into the casing base from the distal base end, wherein the inner casing surface has a shoulder portion extending radially inward and proximally from the distal base end, an axial portion extending proximally from the shoulder portion towards an inner face of the casing head, and a circumferential groove between the distal inner face of the casing head and at least a portion of the axial portion, wherein the circumferential groove has a groove radius greater than a radius of the axial portion; and
a casing body secured to the casing base and having a tubular sleeve portion extending along the central axis from a proximal sleeve end to a distal sleeve end, a proximal body portion connected to the proximal sleeve end and including (i) a sleeve shoulder extending along the shoulder portion of the casing base, (ii) an axial sidewall extending along the axial portion of the casing base, and (iii) a flange protruding radially outward from the axial sidewall and mating with the circumferential groove;
wherein the flange includes a proximal flange portion and a distal flange portion each extending radially outward in an axially spaced-apart orientation with respective outer radial end portions connected by an axial flange sidewall, and wherein the flange defines a locking chamber between the proximal flange portion and the distal flange portion.
11. The ammunition cartridge casing of claim 10 further comprising an annular washer disposed at least partially in the locking chamber.
12. The ammunition cartridge casing of claim 11 , wherein the annular washer has a Shore hardness from D55 to D86 or a Brinell harness from B30 to B101.
13. The ammunition cartridge casing of claim 11 , wherein the annular washer comprises a material selected from ABS plastic, acetal, low density polyethylene, high density polyethylene, high-impact polystyrene, nylon, polycarbonate, polypropylene, polyetherimide, aluminum, aluminum alloy, copper, a copper alloy, brass, and gilding metal.
14. The ammunition cartridge casing of claim 10 , wherein the casing head defines a centrally located primer pocket extending axially into the casing base, wherein the opening is axially spaced from the centrally located primer pocket by a portion of the casing base defining a flash opening between the primer pocket and the casing body.
15. A cartridge casing comprising:
a casing base of a first metal and extending along a central axis from a casing head to a distal base end, the casing base having an inside surface defining
a primer pocket in the casing head, the primer pocket having a first diameter;
an open region situated distally of the primer pocket, the open region having a distal portion with a second diameter and a proximal portion with a third diameter greater than the second diameter; and
an annular wall between the primer pocket and the open region, the annular wall having a distal face and defining a flash opening between the primer pocket and the proximal portion of the open region, the flash opening having an opening diameter smaller than the first diameter and smaller than the third diameter; and
a casing body of a second metal, the casing body secured to the casing base, the casing body having a tubular sleeve portion extending distally from the casing base and having a proximal body portion disposed in the open region of the casing base, wherein the proximal body portion extends along and mates with the inside surface of the open region, the proximal body portion further including a proximal body wall engaging and extending radially inward along the distal face of the annular wall and defining an opening around the flash opening.
16. The cartridge casing of claim 15 further comprising an annular washer within the proximal body portion, the annular washer having an outer diameter greater than the second diameter and spaced from the distal face of the annular wall by a portion of the proximal body portion of the casing body.
17. The cartridge casing of claim 15 , wherein the inside surface of the casing base defines a plurality of facets along the distal portion of the open region.
18. The cartridge casing of claim 15 , wherein the second metal is compositionally distinct from the first metal.
19. The cartridge casing of claim 15 , wherein the second metal is different from the first metal in at least one of a density and a tensile strength.
20. The cartridge casing of claim 15 , wherein the cartridge casing has an ultimate tensile strength of at least 70,000 psi.
21. The cartridge casing of claim 15 further comprising:
a projectile retained in a mouth of the casing body;
a primer in the primer pocket; and
a quantity of propellant in the casing body between the projectile and the primer.
22. The cartridge casing of claim 21 , wherein the cartridge casing is a rifle cartridge.