Firearm projectiles with turbulence-inducing surfaces, firearm cartridges including the same, and associated methods

Abstract

Firearm projectiles with turbulence-inducing surfaces, firearm cartridges including the same, and associated methods. A firearm projectile comprises a projectile body and a turbulence-inducing surface at least substantially enclosing the projectile body. The firearm projectile is at least substantially spherical. The turbulence-inducing surface is configured to induce a drag crisis in a drag coefficient of the firearm projectile when the firearm projectile travels through air with a Reynolds number that is less than 300,000.

1 . (canceled) 
     
     
         2 . The shot shell of  claim 12 , wherein when a shot pellet of the plurality of shot pellets traveling through air has a Reynolds number that is less than 300,000, the shot pellet has a drag coefficient that is less than 0.35. 
     
     
         3 . The shot shell of  claim 12 , wherein each shot pellet of the plurality of shot pellets has a drag coefficient when traveling through air at a given velocity that is at most 0.7 times a drag coefficient of a smooth spherical projectile of the same mass and material composition as the shot pellet and that lacks the turbulence-inducing surface when the smooth spherical projectile travels through air with the given velocity. 
     
     
         4 . The shot shell of  claim 12 , wherein the turbulence-inducing surface of each of the plurality of shot pellets is integral with the respective projectile body of each of the plurality of shot pellets. 
     
     
         5 . The shot shell of  claim 12 , wherein the turbulence-inducing surface of each of the plurality of shot pellets consists of a plurality of non-overlapping surface loci; wherein each surface locus of the plurality of surface loci has a corresponding locus radius, as measured between the surface locus and a center point of the projectile body; wherein each shot pellet of the plurality of shot pellets has a reference radius that is equal to the arithmetic mean of the corresponding locus radii of the plurality of surface loci; wherein each surface locus of the plurality of surface loci further has a corresponding radial deviation that is equal to the corresponding locus radius minus the reference radius; wherein each shot pellet of the plurality of shot pellets is characterized by a roughness metric that is based, at least in part, on the set of corresponding radial deviations of the plurality of surface loci; wherein the roughness metric includes a relative roughness ratio, defined as the ratio of a characteristic roughness depth of the turbulence-inducing surface to a diameter of the shot pellet; wherein the characteristic roughness depth is equal to an arithmetical mean deviation, defined as the arithmetic mean of the absolute values of the set of corresponding radial deviations of the plurality of surface loci; and wherein the absolute value of the relative roughness ratio is at least 0.0001 and at most 0.035. 
     
     
         6 . The shot shell of  claim 5 , wherein the plurality of surface loci includes at least 10,000 surface loci. 
     
     
         7 . The shot shell of  claim 12 , wherein the turbulence-inducing surface of each shot pellet of the plurality of shot pellets includes a plurality of localized surface features, wherein each localized surface feature includes at least one of a depression, an indentation, and a crater. 
     
     
         8 . The shot shell of  claim 7 , wherein at least one localized surface feature includes a depression that is at least substantially surrounded by a raised rim. 
     
     
         9 . The shot shell of  claim 12 , wherein the turbulence-inducing surface of each shot pellet of the plurality of shot pellets includes a plurality of elongate surface features, wherein each elongate surface feature includes at least one of a ridge, an edge, a channel, a groove, and a scratch. 
     
     
         10 . The shot shell of  claim 9 , wherein the plurality of elongate surface features includes a plurality of scratches that are randomly oriented with respect to one another. 
     
     
         11 . The shot shell of  claim 9 , wherein the plurality of elongate surface features include at least one of intersecting and partially overlapping surface features. 
     
     
         12 . A shot shell, comprising:
 a casing that defines an internal volume;   a propellant disposed in the internal volume;   a primer disposed in the internal volume and configured to ignite the propellant;   a wad disposed in the internal volume and separating the propellant and the primer from a payload region of the shot shell; and   a plurality of shot pellets received within the payload region of the shot shell, each of the plurality of shot pellets is at least substantially spherical and comprises:
 a projectile body; and 
 a turbulence-inducing surface at least substantially enclosing the projectile body; wherein the turbulence-inducing surface of each shot pellet of the plurality of shot pellets is configured to induce a drag crisis in a drag coefficient of the shot pellet when the shot pellet traveling through air has a Reynolds number that is less than 300,000. 
   
     
     
         13 . (canceled) 
     
     
         14 . The shot shell of  claim 12 , wherein the shot shell is configured to propel the plurality of shot pellets with a muzzle velocity that is at least 350 meters per second (1,148 feet per second). 
     
     
         15 . A method of manufacturing each shot pellet of the plurality of shot pellets of  claim 12 , the method comprising:
 providing a base projectile that is at least substantially spherical, wherein the base projectile includes a smooth exterior surface; and   forming the turbulence-inducing surface on the exterior surface of the base projectile.   
     
     
         16 . The method of  claim 15 , wherein the providing the base projectile includes providing a projectile precursor that is not substantially spherical and shaping the projectile precursor into the base projectile that is at least substantially spherical. 
     
     
         17 . The method of  claim 15 , wherein the forming the turbulence-inducing surface includes chemically etching the exterior surface of the base projectile with an acid. 
     
     
         18 . The method of  claim 15 , wherein the forming the turbulence-inducing surface includes mechanically deforming the exterior surface of the base projectile. 
     
     
         19 . The method of  claim 18 , wherein the mechanically deforming the exterior surface of the base projectile includes mechanically abrading the exterior surface of the base projectile via a shear process by rolling the base projectile relative to an abrasive belt. 
     
     
         20 . The method of  claim 18 , wherein the mechanically deforming the exterior surface of the base projectile includes abrasively blasting the exterior surface of the base projectile with an abrasive medium that includes one or more of air, water, sand, grit, and pellets. 
     
     
         21 . The shot shell of  claim 12 , wherein each shot pellet of the plurality of shot pellets has a diameter that is at least 2 millimeters (mm) and that is at most 10 mm. 
     
     
         22 . The shot shell of  claim 12 , wherein each shot pellet of the plurality of shot pellets has a density that is at least 6.5 grams per cubic centimeter (g/cc). 
     
     
         23 . The shot shell of  claim 1 , wherein the turbulence-inducing surface of each shot pellet of the plurality of shot pellets includes a plurality of at least partially overlapping depressions, indentations, and/or craters. 
     
     
         24 . The shot shell of  claim 12 , wherein at least 95 wt % of each shot pellet of the plurality of shot pellets is metal.