Duplex Projectile Cartridge and Method for Assembling Subsonic Cartridges for use with Gas-Operated Firearms

Abstract

A duplex projectile cartridge system (e.g., 400 ) for use in a standard rifle (e.g., 10 ) has a front bullet (e.g., 320 ) and a substantially cylindrical back bullet (e.g., 440 ) coaxially aligned with one another. The front bullet's base is held in the cartridge case neck far enough to engage the back bullet's front surface so that the case neck simultaneously bears upon the front bullet and the back bullet. Optionally, the cartridge configuration orients the back bullet and defines one or more gas bypass lumens to allow expanding gas to initially bypass the back bullet and drive the front bullet distally to force an inter-bullet gap (e.g., “IBG” 480 ) upon firing.

What is claimed is: 
     
         1 . A duplex projectile system (e.g.,  100 ,  200 ,  300 ,  400 ,  500 ,  700 ) for use in a standard military or tactical rifle system (e.g.,  10 ) of a selected caliber, comprising:
 (a) a cartridge case (e.g.,  150 ) with a substantially cylindrical body which is symmetrical about a central axis extending from a substantially closed proximal head to a substantially open distal mouth or lumen, where the body defines an interior volume for containing and protecting a propellant charge, and wherein the cartridge neck is configured to be substantially cylindrical segment having a cylindrical interior lumen in said selected caliber extending from the distal neck end which defines the neck lumen, and wherein the cartridge neck lumen has an interior sidewall with a selected axial neck length; and   (b) a front bullet and a back bullet coaxially aligned with one another and with the case's central axis and held in the case neck (e.g.,  158 ) by inwardly squeezing force applied via the case neck, said case neck squeezing force bearing simultaneously upon the front bullet (e.g.,  120 ) and the back bullet (e.g.,  140 ).   
     
     
         2 . The duplex projectile system of  claim 1 , wherein said front bullet (e.g.,  120 ,  220 ) has a body with a tapered or contoured ogive terminating distally in a tip, and wherein said front bullet body has a proximal or rearward portion with a rear cylindrical sidewall segment terminating proximally in a tapered sidewall segment which then transitions to a rearwardly projecting frustoconical boat tail (e.g.,  126 ,  226 ) which is symmetrically defined around the front bullet body's central axis, and the frustoconical boat tail terminates proximally or rearwardly in a substantially planar transverse rear end or surface configured to be received snugly within a front cavity of the back bullet (e.g.,  140 ,  240 ). 
     
     
         3 . The duplex projectile system of  claim 2 , wherein said front bullet (e.g.,  120 ,  220 ) has an open distal tip which defines a front facing cavity or opening symmetrically defined around the bullet's central axis, 
     
     
         4 . The duplex projectile system of  claim 2 , wherein said back bullet (e.g.,  140 ,  240 ) is configured with a full caliber sidewall having distal open tip (e.g.,  142 ,  242 ) and lacking the conventional rounded or tapered nose and terminates at the front (or distally) in a very wide full caliber distal or front-facing concavity which defines a front facing opening symmetrically defined around the bullet's central axis, and that front facing concavity is precisely configured to snugly receive, center and support the rearwardly projecting frustoconical boat tail of the coaxially aligned front bullet. 
     
     
         5 . The duplex projectile system of  claim 1 , wherein said front bullet (e.g.,  320 ) has a body with a tapered or contoured ogive terminating distally in a full metal jacket clad tip or an open tip which defines a front facing cavity or opening where the front bullet's body is symmetrically defined around the bullet's central axis, and wherein said front bullet body has a proximal or rearward portion with a rear cylindrical sidewall segment terminating proximally in a substantially planar flat transverse base (e.g.,  328 ) which is symmetrically defined around the front bullet body's central axis, and the front bullet's flat base provides a surface configured to be received snugly against a front substantially planar wadcutter surface (e.g.,  342 ,  442 ,  542 ,  742 ) of the back bullet (e.g.,  340 ,  440 ,  540 ,  740 ). 
     
     
         6 . The duplex projectile system of  claim 4 , wherein said back bullet (e.g.,  340 ) is configured with full caliber sidewall extending from the distal or front substantially planar wadcutter surface and symmetrically defined around the back bullet's central axis, wherein the front facing substantially planar full caliber wadcutter surface of the back bullet is precisely configured to snugly receive and support the proximal flat base of the coaxially aligned front bullet. 
     
     
         7 . The duplex projectile system of  claim 1 , wherein said front bullet is fabricated from lead, tungsten, copper alloy cladded lead, copper alloy cladded tungsten or C36000 brass. 
     
     
         8 . The duplex projectile system of  claim 1 , wherein said back bullet is fabricated from lead, tungsten, copper alloy cladded lead, copper alloy cladded tungsten or C36000 brass. 
     
     
         9 . The duplex projectile system of  claim 1 , wherein cartridge case is manufactured to one of (a) 7.62 NATO ammunition specifications, (b) SS109/M855 5.56 NATO ammunition specifications or A191/MK 248 .300 Winchester magnum ammunition specifications. 
     
     
         10 . A method for making a duplex projectile system for use in a standard military or tactical rifle system in a selected caliber, comprising the method steps of:
 (a) providing a cartridge case with a substantially cylindrical body which is symmetrical about a central axis extending from a substantially closed proximal head to a substantially open distal mouth or lumen, where the body defines an interior volume for containing and protecting a propellant charge, and wherein the cartridge neck is configured to be substantially cylindrical segment extending from the distal neck end which defines the neck lumen rearwardly or proximally to an angled shoulder segment which flares out to the cylindrical body sidewall, and wherein the cartridge neck has a neck lumen interior sidewall with a selected axial neck length;   (b) providing a front bullet with a rear or proximal surface of the selected caliber;   (c) providing a back bullet with substantially cylindrical full caliber sidewall terminating in a distal front surface on one end and a proximal base on the other end;   (d) inserting a selected quantity of a selected propellant or powder into the case's interior volume through the cartridge case mouth; and   (e) inserting the back bullet's proximal base into the cartridge case mouth;   (f) driving the back bullet axially and down into the cartridge case's mouth so that the back bullet's distal or forward front surface is recessed into the cartridge case mouth and driven approximately half way along the case neck sidewall's axial length so that about half the case neck sidewall remains uncovered by the now inserted back bullet, when looking into the cartridge case mouth.   
     
     
         11 . The method for making a duplex projectile system of  claim 10 , further comprising the steps of:
 (g) inserting the front bullet's rear or proximal end into the cartridge case mouth;   (h) driving the front bullet axially and down into the cartridge case neck far enough to engage or provide a selected gap from the back bullet's distal front surface so that the case neck supports the rear of the front bullet and the front of the rear bullet and coaxially aligns the front bullet and the rear bullet with the case body's central axis, thereby causing a substantially uniform case neck tension to hold the front bullet and back bullet in the case neck by inwardly squeezing force applied via the case neck simultaneously bearing upon the front bullet and the back bullet.   
     
     
         12 . The method for making a duplex projectile system of  claim 11 , wherein said back bullet is driven into said case to expose approximately 0.150 inches of case sidewall. 
     
     
         13 . The method for making a duplex projectile system of  claim 12 , wherein said front bullet is driven approximately 0.150 inches into said case mouth to abut said back bullet's distal front surface, while not driving said back bullet further into said cartridge case's interior. 
     
     
         14 . The method for making a duplex projectile system of  claim 10 ,
 (g) inserting the front bullet's rear or proximal end into the cartridge case mouth;   (h) driving the front bullet axially and down into the cartridge case neck far enough to engage the back bullet's proximal front meplat surface (e.g.,  642 ) so that the case neck supports the front bullet and drives the distal meplat of the back bulled proximally and out of contact with the neck, thereby defining an annular gas-bypass lumen between the cartridge and the back bullet's distal meplat.   
     
     
         15 . The method for making a duplex projectile system of  claim 14 , wherein said annular gas-bypass lumen between the cartridge and the back bullet's distal meplat has an outside diameter of 0.313 to 0.318 inches for a back bullet caliber of 0.308 inches. 
     
     
         16 . A duplex projectile system for use in a standard military or tactical rifle system of a selected caliber, comprising:
 (a) a cartridge case with a substantially cylindrical body which is symmetrical about a central axis extending from a substantially closed proximal head to a substantially open distal mouth or lumen, where the body defines an interior volume for containing and protecting a propellant charge, and wherein the cartridge neck is configured to be substantially cylindrical segment having a cylindrical interior lumen in said selected caliber extending from the distal neck end which defines the neck lumen rearwardly or proximally to an angled shoulder segment which flares out to the cylindrical body sidewall, and wherein the cartridge neck has a neck lumen interior sidewall with a selected axial neck length;   (b) a front bullet and a back bullet coaxially aligned with one another and with the case's central axis; and   (c) wherein the duplex projectile system is optimized to provide subsonic ammunition which is adapted for use in a standard rifle equipped with a suppressor or silencer.   
     
     
         17 . The duplex projectile system of  claim 16 , wherein said front and back bullets generate a higher gas pressure and when fired and reach a selected subsonic velocity (e.g. 1050 fps) while functioning in a standard rifle without requiring any adjustment to rifle's gas system. 
     
     
         18 . The duplex projectile system of  claim 16 , wherein said front and back bullets are stabilized to provide consistent shot-to-shot subsonic accuracy in a standard rifle's barrel. 
     
     
         19 . The duplex projectile system of  claim 18 , wherein said front and back bullets, are aligned and configured within said casing to define at least one gas bypass lumen so that, when fired, propellant gasses bypass the back bullet and pressurize the rear surface or base (e.g.,  328 ) of the front bullet (e.g.,  320 ) which is thereby forced into the rifle's barrel (e.g.,  14 ) by said bypassing gas;
 and wherein said back bullet is then driven into said barrel thereby trapping said bypassing gas between said front bullet and said back bullet, to provide an inter bullet gap (e.g., “IBG”  480 ) between said front bullet and said rear bullet;   whereby said front bullet and said rear bullet each engage the barrel's rifling separately and independently, and each are individually stabilized by the rifling.   
     
     
         20 . The duplex projectile system of  claim 16 , wherein said back bullet includes at least one longitudinal gas port defined between the back bullet's sidewall and the back bullet's distal end;
 said gas port being configured to allow expanding gas to pass distally beside or through the back bullet's body and pressurize the space behind the front bullet and drive the front bullet distally down the firearm's bore;   wherein said port is configured to direct said gas to force an inter-bullet gap (e.g., “IBG”  480 ) between the front bullet and the back bullet upon firing; and   (d) wherein the duplex projectile cartridge is optimized to provide subsonic ammunition which is adapted for use in a standard rifle equipped with a suppressor or silencer.   
     
     
         21 . The duplex projectile system of  claim 20 , wherein said front and back bullets generate a higher gas pressure and when fired and reach a selected subsonic velocity (e.g. 1050 fps) while functioning in a standard rifle without adjusting the gas system. 
     
     
         22 . The duplex projectile system of  claim 21 , wherein said front and back bullets are stabilized to provide consistent shot-to-shot subsonic accuracy in standard rifles. 
     
     
         23 . The duplex projectile system of  claim 22 , wherein said front bullet is fabricated from lead, tungsten, copper alloy cladded lead, copper alloy cladded tungsten or C36000 brass. 
     
     
         24 . The duplex projectile system of  claim 22 , wherein said back bullet is fabricated from lead, tungsten, copper alloy cladded lead, copper alloy cladded tungsten or C36000 brass. 
     
     
         25 . The duplex projectile system of  claim 16 , wherein said cartridge case is manufactured to one of (a) 7.62 NATO ammunition specifications, (b) SS109/M855 5.56 NATO ammunition specifications or A191/MK 248 .300 Winchester magnum ammunition specifications.