Reduced drag projectiles
A cartridge comprising an elongate rifle bullet with a plurality of circumferential grooves having overmolded polymer therein defining embedded polymer rings. The cartridge further having a case and propellant. The polymer rings have an outer surface that is flush with, that is, conforming to the outer surface of the body. The polymer may have be selected to have a favorable coefficient of friction with respect to the barrel. The bands offering reduction of the metal to metal contact between the bullet and the barrel while not diminishing the ballistic coefficient of the bullet.
1. A low caliber ammunition cartridge, comprising:
a case comprising a base portion and a case wall extending forward from the base portion to a forward edge of the case wall defining a case cavity and a forward case mouth
propellant disposed inside the case cavity for producing a quantity of propellant gas;
a primer housing disposed in a hole defined by the base portion of the case, and a priming material disposed inside the primer housing for igniting the propellant;
a projectile secured in the mouth of the casing, the projectile comprising a unitary projectile body having a rearward tail portion, a forward nose portion, and a barrel engaging portion extending between and unitary with the nose portion and the tail portion, the barrel engaging portion including a monolithic portion, the monolithic portion having three circumferential grooves spaced intermediate the tail portion and the nose portion, each of the circumferential grooves has an undercut;
the projectile further comprising three overmolded polymer bands disposed in the three circumferential grooves, each of the three overmolded bands conforming to the shape of the respective groove.
2. The low caliber ammunition cartridge of claim 1 wherein at least one of the three overmolded bands has an outer convex surface that extends radially beyond the outer surface of the projectile body providing a sealing surface with an interior surface of the case wall.
3. A low caliber ammunition cartridge, comprising:
a case comprising a base portion and a case wall extending forward from the base portion to a forward edge of the case wall defining a case cavity and a forward case mouth
propellant disposed inside the case cavity for producing a quantity of propellant gas;
a primer housing disposed in a hole defined by the base portion of the case, and a priming material disposed inside the primer housing for igniting the propellant;
a projectile secured in the mouth of the casing, the projectile comprising a unitary projectile body having a rearward tail portion, a forward nose portion, and a barrel engaging portion extending between and unitary with the nose portion and the tail portion, the barrel engaging portion having a monolithic portion and a plurality of circumferential grooves positioned on the monolithic portion;
the projectile further comprising a plurality of overmolded polymer bands disposed respectively in each of the plurality of circumferential grooves, each band conforming to the shape of the respective groove and secured therein;
an upper portion of the case wall is swaged or crimped inwardly to form a seal between the case wall and the projectile for closing the opening and preventing communication between the propellant in the cavity and an atmosphere outside of the ammunition cartridge; and
the forward edge of the case wall is at one of the plurality of overmolded bands.
4. The low caliber ammunition cartridge of claim 3 , wherein each band is secured within the respective groove at least partially by said band being adhered to the respective groove wall surface by overmolding of each said band into the respective groove.
5. The low caliber ammunition cartridge of claim 3 wherein at least one of the plurality of bands has an exterior convex surface that provides a sealing surface with an interior wall surface of the case wall of the casing, the exterior surface having a diameter greater than the greatest diameter of the barrel engaging portion of the projectile body.
6. The low caliber ammunition cartridge of claim 3 , wherein there are three overmolded bands engaged with the interior surface of the case wall.
7. The low caliber ammunition cartridge of claim 3 , wherein each of the plurality of grooves has a curved interior surface whereby in a cross section taken along the axis of the projectile body, the juncture between the groove surface and the overmolded ring is C-shaped.
8. The low caliber ammunition cartridge of claim 3 , wherein each overmolded band has a width at the outer surface of respective band and each said band has a greater width inward of said outer width thereby securing the band in the respective groove.
9. The low caliber ammunition cartridge of claim 3 , wherein the plurality of bands comprise at least two different colors and the colors correlate to a characteristic of the projectile or cartridge.
10. The low caliber ammunition cartridge of claim 3 , wherein the color of the forwardmost band is selected from a plurality of colors and the color correlates with a characteristic of the projectile or cartridge.
11. The low caliber ammunition cartridge of claim 3 , wherein the projectile body further has a rearward aperture extending axially into a rearwardly face of the tail portion, and the projectile further comprises a plug overmolded in the aperture.
12. A low caliber ammunition cartridge, comprising:
a case comprising a base portion and a case wall extending forward from the base portion to a forward edge of the case wall defining a case cavity and a forward case mouth
propellant disposed inside the case cavity for producing a quantity of propellant gas;
a primer housing disposed in a hole defined by the base portion of the case, and a priming material disposed inside the primer housing for igniting the propellant;
a projectile secured in the mouth of the casing, the projectile comprising a unitary projectile body having an exterior surface, a rearward tail portion, a forward nose portion with a nose tip, and a barrel engaging portion extending between and unitary with the nose portion and the tail portion, the body having an interior surface defining a central cavity extending rearwardly from the nose tip, whereby a projectile wall is defined between the interior surface and the exterior surface, the projectile body having a circumferential groove cut inwardly into the exterior surface of the projectile body, the interior surface not having any structure thereon reflective of the circumferential groove;
an overmolded polymer band in the groove, the band having an outer surface that is flush with and continuous with respect to the exterior surface of the projectile body.
13. The low caliber ammunition cartridge of claim 12 wherein the forward nose portion has an ogive portion and the circumferential groove is positioned on said ogive portion.
14. The low caliber ammunition cartridge of claim 12 further comprising a plurality of circumferential grooves rearward of the cavity, each of the plurality of circumferential grooves having an overmolded band therein with an outer surface, said outer surface flush with the exterior surface of the projectile body.
15. The low caliber ammunition cartridge of claim 12 wherein there is not a gap between the circumferential band and the projectile body.
16. The low caliber ammunition of claim 12 wherein the projectile comprises a central axially extending cavity at the rearward face of the tail portion, and wherein there is an overmolded plug in said central aperture.