Duplex Projectile Cartridge and Method for Assembling Subsonic Cartridges for use with Gas-Operated Firearms
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.
This application is a continuation of International Application No. PCT/US2015/47618, filed on Aug. 29, 2015, which claims the benefit of U.S. provisional patent application No. 62/044,175, entitled Duplex Projectile System and Method, which was filed on Aug. 29, 2014, and U.S. provisional application No. 62/104,987, entitled Duplex Projectile Cartridge and Method for Assembling Subsonic and Supersonic Cartridges for use with Gas-Operated Firearms, which was filed on Jan. 19, 2015, the entire disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention relates to ammunition used in firearms and more particularly to ammunition for use with military or tactical gas-operated semi-automatic or select fire rifles and particularly ammunition intended for use in suppressor-equipped gas-operated rifles.
BACKGROUNDModern firearms such as rifles (e.g., 10, as shown in
A firearm's action is used to fire the cartridge. For example, the action can include a striker that carries a firing pin. The action can be used to advance the cartridge into a firing chamber ahead of firing. While in the firing chamber, a trigger mechanism can be used to release a sear to cause the firing pin to strike the primer, causing the primer to ignite. The primer's ignition is directed to the powder, which burns within the casing. The powder burns within the casing to generate a rapidly expanding gas, which propels the projectile out of the casing and through the barrel.
Modern gas-operated semi-automatic or select fire rifles such as the M4, M16, AR-15, AR-10, XM-110 or SR-25 (e.g., rifle 10 as illustrated in
[Military marksmen, police marksmen and others who are trained in using such standard or issued rifles have expectations about how these rifles will function when using issued ammunition and if those training expectations are unmet by a new rifle or ammunition offering, the new offering will almost certainly be rejected as unworkable. When the standard ammunition cycles reliably in the standard rifle and shoots with acceptable precision to a specified point of impact at a selected distance, that reliable success defines the training expectations for the standard rifle system (e.g., 10).
In certain operational environments, there is a desire for ammunition which sends more than one projectile for each cartridge fired, but the prior art attempts have all failed to meet the established training expectations for users of the standard rifles. A number of unusual ammunition configurations have been developed for use by soldiers and military marksman, and several ammunition developers have experimented with ammunition having two or more projectiles (such as the Vietnam era's “M198” duplex or “salvo” cartridge (MilSpec MIL-C-60131, as shown in
There is a need, therefore, for a novel ammunition configuration which provides the benefits of multiple projectiles fired with each cartridge, but which does not frustrate the training expectations for users of the standard rifles (with or without suppressors), and does not create a “salvo effect” or provide a dangerously enlarged and imprecise beaten zone around the aim point or target. The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to define relevant nomenclature and illustrate one exemplary technology area where some examples described herein may be practiced.
SUMMARYThe duplex projectile system and method of the present invention provides an accurate and reliable novel ammunition configuration which provides the fire superiority benefits of multiple projectiles fired with each cartridge while preserving the training expectations for users of the standard military or tactical rifles (e.g., AR-10 SR-25, M14 or M21), and which also provides precise, repeatable and accurate impacts on small targets over selected engagement ranges, meaning the precision shooter can fire two projectiles with each trigger squeeze and deliver accurate hits on small targets while avoiding unintended hits on adjacent objects or areas near the intended target.
The duplex projectile system of the present invention is optimized to provide subsonic ammunition which is adapted for use in a standard rifle (e.g., 10) equipped with a suppressor or silencer (e.g., 12). “Subsonic” in this context means ammunition which propels a projectile at a velocity intentionally selected to be below the speed of sound (e.g., below 1126 feet per second (fps) in dry air at about 70° F. of slower than Mach 1), and subsonic ammunition is usually selected for use with a suppressor or silencer (e.g., 12) because the passing projectile won't generate the supersonic “crack” noise heard by those in the vicinity of a projectile having a velocity faster than the speed of sound (e.g., more than 1126 fps in dry air at about 70° F. or faster than Mach 1). Briefly, that supersonic crack is created when a supersonic projectile passes through the air and creates a series of pressure waves in front of it, similar to the bow waves created by a boat. These waves travel at the speed of sound, and since the speed of the projectile is higher than those “bow” waves, the waves are forced or compressed together to create a shock wave which is audible as the supersonic crack which travels along the trajectory of the passing projectile. When a gas operated rifle (e.g. 10) is equipped with a suppressor (e.g., 12) and the shooter wants to avoid making excessive noise, the shooter will typically use subsonic ammunition which creates significantly less gas port pressure than when firing standard (supersonic) ammunition. As noted above, traditional subsonic ammunition often creates problems in that the rifle's gas system may not cycle reliably, so a shooter who doesn't want to modify the gas system of the rifle is required to shoot the louder standard supersonic ammunition.
The subsonic embodiments of the duplex projectile cartridge system of the present invention create significantly more pressure at the gas port (e.g., 18) than standard single projectile subsonic cartridges, thus allowing standard rifles (e.g., 10) to function without requiring a gas system adjustment. This benefit is important because the first and second bullets of the duplex system of the present invention weigh more than any single bullet ever manufactured for use in a standard service rifle (i.e., AR-10 SR-25, M14 or M21). The two bullets require a higher gas pressure to reach the upper end of subsonic velocities (e.g. 1050 fps). This higher gas pressure makes it possible for a user's standard rifle to fire a subsonic load quietly and function without requiring adjustment of the gas system. No other ammunition can provide reliable gas system operation and consistent shot-to-shot subsonic accuracy in standard rifles.
Significantly, this level of performance is achieved in part because the barrels in standard rifles were discovered to provide surprising stability for the first and second projectiles in the duplex projectile system of the present invention. A standard rifle (e.g., 10) typically has a barrel (e.g., 14) with rifling having a twist rate of between one (360 degree) twist in ten inches to one in twelve inches and is designed to stabilize a single projectile of 147 grains to 175 grains travelling at the standard velocity (e.g., 2650 fps-2800 fps). In the present invention, the front and back bullets are each stabilized in that standard twist-rate rifle barrel (e.g., 14 at subsonic velocity. The applicants have discovered how to provide the enhanced terminal ballistic benefits of firing a single long and heavy bullet at subsonic velocities, but without requiring a different barrel; a single long bullet that weighed the same amount as the duplex system's front and back bullets would be too long to be stabilized in a standard twist-rate rifle.
The duplex projectile system and method of the present invention are specifically designed for use by trained users of modern gas-operated semi-automatic or select fire standard rifles (such as the rifle type illustrated in
As also noted above, military marksmen, police marksmen and others who are trained in using such standard or issued rifles have expended significant effort at great expense and so have well established expectations about how these rifles will function when using any issued ammunition, and those hard-earned training expectations must be met by any new rifle or ammunition offering, meaning that the new ammunition must cycle reliably in the marksman's standard rifle and shoot with at least an acceptable level of precision to a specified point of impact at a selected distance.
The duplex projectile cartridge of the present invention includes a duplex bullet assembly comprising a front bullet and a back bullet which are carried in a cartridge case resembling the cartridge case for the M118LR (7.62 NATO) cartridge (or case 150 for the M118 cartridge of
The front bullet is preferably configured with an open tip or a pointed conical polymer ballistic tip and is fabricated or machined from one or more selected metals. The body of the front bullet has a tapered or contoured ogive terminating distally in an open tip which defines a front facing cavity or opening symmetrically defined around the central axis, and the front facing cavity may be configured to receive a polymer ballistic tip insert. The diameter or “caliber” of the front bullet body is preferably selected from among SAAMI standard calibers (e.g., nominally 0.308 inches or 7.62 mm) for use in a selected rifle (e.g., an FN-FAL, AR-10, SR-25, M14 or M21). The central portion of the body of the front bullet preferably includes a sidewall segment carrying a plurality of circumferential grooves of shallow depth and spaced longitudinally along the bullet sidewall from one another. The proximal or rearward portion of the body of the front bullet preferably has rear cylindrical sidewall segment terminating proximally in a tapered sidewall segment which then transitions to a rearwardly projecting frustoconical “boat tail” 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 the front cavity of the back bullet.
The back bullet is preferably configured with an open tip and is fabricated or machined from one or more selected metals. The largest outer diameter or “caliber” of the back bullet is substantially identical to the front bullet body diameter (e.g., for the illustrative example, nominally 0.308 inches or 7.62 mm). The body of the back bullet lacks the conventional rounded or tapered nose and terminates at the front (or distally) in a very wide distal or front-facing concavity which defines a front facing opening symmetrically defined around the 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. The central portion of the body of the back bullet preferably includes a sidewall segment carrying a plurality of circumferential grooves of shallow uniform depth but varying width and those circumferential grooves are spaced longitudinally along the back bullet sidewall from the distal or front end to the proximal or rear end. The proximal or rearward portion of the body of the back bullet preferably has rear cylindrical sidewall segment terminating proximally in a substantially planar transverse rear end or surface which provides a flat base back bullet configuration.
The method of assembling the duplex ammunition of this embodiment is to provide a vertically oriented standard military cartridge case which has been primed, insert a selected propellant or powder charge into the case's interior volume through the cartridge case mouth, insert a back bullet's proximal base into the cartridge case mouth and drive the back bullet down into the cartridge case's mouth so that the back bullet's distal or forward edge is recessed into the cartridge case mouth and driven 150 thousandths of an inch into the case neck, such that approximately 150 thousandths of the case neck interior is uncovered by the now inserted back bullet, when looking into the cartridge case mouth. Next a front bullet's proximal boat-tail base is inserted into the cartridge case mouth and the front bullet is driven down and seated into the back bullet's open distal end or mouth so that the front bullet's proximal boat-tail is received in and centered by the rear bullet's distal or forward surfaces when the front bullet is recessed into the cartridge case mouth and driven 150 thousandths of an inch into the case neck, so that once the duplex cartridge is assembled, the case neck supports the rear of the front bullet and the front of the rear bullet simultaneously.
In an alternative embodiment, the back bullet has a “wad cutter” configuration. In this second embodiment, the front bullet is preferably configured with a flat circular base and the body of the front bullet has a tapered or contoured ogive terminating distally in a distal solid tip or a front facing cavity or opening symmetrically defined around the central axis, and the front facing cavity may be configured to receive a polymer ballistic tip insert. The diameter or “caliber” of the front bullet body is preferably selected from among SAAMI standard calibers (e.g., nominally 0.308 inches or 7.62 mm) for use in a selected rifle (e.g., an FN-FAL, AR-10, SR-25, M14 or M21). The central portion of the body of the front bullet preferably includes a sidewall segment carrying a plurality of circumferential grooves of shallow depth and spaced longitudinally along the bullet sidewall from one another. The proximal or rearward portion of the body of the front bullet preferably has rear cylindrical sidewall segment terminating proximally in a transverse flat, circular base which is symmetrically defined around the front bullet body's central axis, and the substantially planar transverse rear flat base surface is configured to abut a substantially planar “wad-cutter” front surface of the back bullet.
The back “wad cutter” bullet is fabricated or machined from a selected metal or is configured with a cladding metal jacket over a lead core. The diameter or “caliber” of the back bullet is substantially identical to the front bullet body diameter (e.g., for the illustrative example, nominally 0.308 inches or 7.62 mm). The body of the back bullet lacks the conventional rounded or tapered nose and terminates at the front (or distally) in a full-diameter substantially planar and circular “wad-cutter” front surface symmetrically defined around the central axis, and that “wad-cutter”front surface is precisely configured to snugly abut and support the flat base of the coaxially aligned front bullet. The central portion of the body of the back bullet preferably includes a sidewall segment carrying a plurality of knurled sections or circumferential grooves of shallow uniform depth but varying width and those circumferential grooves are spaced longitudinally along the back bullet sidewall from the distal or front end to the proximal or rear end. The proximal or rearward portion of the body of the back bullet preferably has rear cylindrical sidewall segment terminating proximally in a substantially planar transverse rear end or surface which provides a flat base back bullet configuration.
Another (third) embodiment includes a front bullet configured with a flat circular base and the body of the front bullet has a tapered or contoured ogive terminating distally in a distal solid tip or a front facing cavity or opening symmetrically defined around the central axis, and the front facing cavity may be configured to receive a polymer ballistic tip insert. The diameter or “caliber” of the front bullet body is preferably selected from among SAAMI standard calibers (e.g., nominally 0.308 inches or 7.62 mm) for use in a selected rifle (e.g., an FN-FAL, AR-10, SR-25, M14 or M21). The central portion of the body of the front bullet preferably includes a sidewall segment carrying a plurality of circumferential grooves of shallow depth and spaced longitudinally along the bullet sidewall from one another. The proximal or rearward portion of the body of the front bullet preferably has rear cylindrical sidewall segment terminating proximally in a transverse flat, circular base which is symmetrically defined around the front bullet body's central axis, and the substantially planar transverse rear flat base surface is configured to abut a substantially planar “wad-cutter” front surface of the back bullet.
Another (fourth) embodiment provides a duplex projectile system ammunition assembly and a surprisingly effective method for creating separation between the first and second bullets within the rifle's bore. Upon firing, the cartridge's ignited powder creates an expanding gas bubble which initially urges both the front and back bullets distally into the barrel's leade, where the front bullet engraves itself on the rifling and begins to accelerate both in its stabilizing rotation about the bullet's central axis and in its travel distally down the bore toward the muzzle. The front bullet is initially pushed by the back bullet. A plurality of ports or longitudinal gas-ducting grooves or channels are defined in the distal or forward portion of the back bullet to allow expanding gas flowing distally into the barrel behind the distally moving front bullet, to pressurize the base of the front bullet and force it distally down the bore while the back bullet is moving slightly more slowly, thereby creating an inter-bullet gap between the distally forced accelerating front bullet and the distal or front edge of the slower back bullet as both bullets travel distally down the bore. This inter bullet gap defines a captive or trapped volume of expanding gas between the front and back bullets as both travel distally down the bore and allows each bullet to accelerate independently. Within the barrel, each bullet is also independently spin stabilized by the rifling, so the rifling twist rate need not be optimized for a very, very long and heavy (e.g., 330 grains) and instead a standard twist rate stabilizes each bullet separately.
The above and still further features and advantages of the present invention will become apparent upon consideration of the following detailed description of a specific embodiment thereof, particularly when taken in conjunction with the accompanying drawings, wherein like reference numerals in the various figures are utilized to designate like components.
Applicant's initial development work led to creation of the first embodiment of the duplex projectile system and method of the present invention, as illustrated in
Referring first to
Front bullet 120 and the back bullet 140 are coaxially aligned with one another and with the case's central axis 150A and are held in case neck 158 by inwardly squeezing circumferential force (or “neck tension”) applied via the case neck 158 simultaneously bearing upon and supporting front bullet 120 and back bullet 140, as shown in
Front bullet 120 is preferably configured with an open tip 122 or a pointed conical metal alloy or polymer ballistic tip (not shown) and is fabricated or machined from one or more selected metals (e.g., lead, tungsten, copper alloy cladded lead, copper alloy cladded tungsten or C36000 brass). The body of the front bullet has a tapered or contoured ogive terminating distally in open tip 122 which defines a front facing cavity or opening symmetrically defined around the bullet's central axis, and the front facing cavity may be configured to receive a metal alloy or polymer ballistic tip insert (not shown). The diameter or “caliber” of the front bullet body is preferably selected from among SAAMI standard calibers (e.g., nominally 0.308 inches or 7.62 mm) for use in a selected rifle (e.g., 10). The central portion of the body of the front bullet preferably includes a sidewall segment carrying a plurality of distally projecting radial sidewall segments separated by circumferential grooves of shallow depth (e.g., 14-24 one thousandths of an inch) and spaced longitudinally along the bullet sidewall from one another. The proximal or rearward portion of the body of the front bullet preferably has rear cylindrical sidewall segment terminating proximally in a tapered sidewall segment which then transitions to a rearwardly projecting frustoconical boat tail 126 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 128 configured to be received snugly within a front cavity of back bullet 140.
Back bullet 140 is preferably configured with a distal open tip 142 and is fabricated or machined from one or more selected metals (e.g., lead, tungsten, copper alloy cladded lead, copper alloy cladded tungsten or C36000 brass). The diameter or “caliber” of back bullet 140 is substantially identical to the front bullet body diameter (e.g., for the illustrative example, nominally 0.308 inches or 7.62 mm). The body of back bullet 140 lacks the conventional rounded or tapered ogive or nose and terminates at the front (or distally) in a very wide distal or front-facing concavity which defines a front facing opening 142 symmetrically defined around the bullet's central axis, and that front facing concavity 142 is precisely configured to snugly receive, center and support the rearwardly projecting frustoconical boat tail 126 of the coaxially aligned front bullet 120.
The central portion of the body of the back bullet preferably includes a sidewall segment carrying a plurality of distally projecting radial sidewall segments separated by circumferential grooves of shallow uniform depth (e.g., 14-24 one thousandths of an inch) but varying width and those circumferential grooves are spaced longitudinally along the back bullet sidewall from the distal or front end to the proximal or rear end. The proximal or rearward portion of the body of the back bullet preferably has rear cylindrical sidewall segment terminating proximally in a substantially planar transverse rear end or base surface 146 which provides a flat-base configuration for back bullet 140. When front bullet boat tail 126 is seated within back bullet cavity 142, there is a tapered annular gap of about 0.005 inches separating the outer diameter surface of front bullet boat tail 126 from the interior surface of back bullet cavity 142, as best seen in the enlarged detail view of
Alternative embodiments of the duplex cartridge system (e.g., 200) and alternatives for the front bullet (e.g., 220, 220A) and back bullet (e.g., 240, 240A) are illustrated in
Referring now to
Back bullet 240 (see
The central portion of the body of the back bullet preferably includes a sidewall segment carrying a plurality of distally projecting radial sidewall segments separated by circumferential grooves of shallow uniform depth (e.g., 14-24 one thousandths of an inch) but varying width and those circumferential grooves are spaced longitudinally along the back bullet sidewall from the distal or front end to the proximal or rear end 246. The proximal or rearward portion of the body of the back bullet preferably has rear cylindrical sidewall segment terminating proximally in a substantially planar transverse rear end or base surface 246 which provides a flat-base configuration for back bullet 240. When front bullet boat tail 226 is seated within back bullet cavity 242, there is a tapered annular gap of about 0.005 inches separating the outer diameter surface of front bullet boat tail 226 from the interior surface of back bullet cavity 242, as best seen in the enlarged detail view of
Another embodiment of the duplex cartridge system (e.g., 200) provides alternatives for the front bullet (e.g., 220A) and back bullet (e.g., 240A) as illustrated in
The central portion of the body of the front bullet preferably includes a sidewall segment carrying a plurality of distally projecting radial sidewall segments separated by circumferential grooves of shallow depth (e.g., 6-24 one thousandths of an inch) and spaced longitudinally along the bullet sidewall from one another. The proximal or rearward portion of the body of the front bullet preferably has rear cylindrical sidewall segment terminating proximally in a tapered sidewall segment which then transitions to a rearwardly projecting frustoconical boat tail 226A which is symmetrically defined around the front bullet body's central axis, and the frustoconical boat tail 226A terminates proximally or rearwardly in a substantially planar transverse rear end or surface 228A configured to be received snugly within front cavity 242 of back bullet 240B.
Back bullet 240B (see
The method of assembling the duplex cartridge system (e.g., 100 or 200) is to provide a vertically oriented standard military cartridge case 150 which has been primed, insert a selected propellant or powder charge (e.g., 160 or 260, such as Hodgdon H4350 or H1000) into the case's interior volume through the cartridge case mouth lumen (e.g., 154), insert a back bullet (e.g., 140, 240, 240B) with the back bullet's proximal base into the cartridge case mouth 154 and drive the back bullet axially and proximally down into the cartridge case's mouth so that the back bullet's distal or forward edge is recessed into the cartridge case mouth and driven substantially half way down the neck, or one hundred fifty thousandths of an inch into the case neck 158, such that approximately half (or one hundred fifty thousandths) of the case neck lumen's interior sidewall is uncovered by the now inserted back bullet, when looking into the cartridge case mouth. Next a front bullet (e.g., 120, 220 or 220A) proximal boat-tail base is inserted into the cartridge case mouth 154 and the front bullet is driven axially down or proximally and seated into the back bullet's open distal end or mouth (e.g., 142) so that the front bullet's proximal boat-tail (e.g., 126) is received in and centered by the rear bullet's distal or forward surfaces when the front bullet is recessed into the cartridge case mouth and driven one hundred fifty thousandths of an inch into the case neck, so that once the duplex cartridge system (e.g., 100 or 200) is assembled, the case neck 158 supports the rear of the front bullet and the front of the rear bullet simultaneously.
Testing of prototype duplex cartridge systems (e.g., 100 or 200) of the present invention for embodiments intended to generate projectile velocities that are substantially subsonic or transonic was confirmed with chronometer testing to confirm muzzle velocities (e.g., the shots fired for the target shown in
As noted above, to meet the normal (supersonic) specification, the ammunition needs to supply 10,500 psi at the gas port to reliably cycle the action. Referring back to
An alternative embodiment is illustrated in
Front bullet 320 and back bullet 340 are coaxially aligned with one another and with the case's central axis 150A and are held in case neck 158 by inwardly squeezing circumferential force (or “neck tension”) applied via the case neck 158 simultaneously bearing upon and supporting front bullet 320 and back bullet 340, as shown in
Back bullet 340 is fabricated or machined from a selected metal or is configured with a cladding metal jacket over a lead core. The diameter or “caliber” of the back bullet is substantially identical to the front bullet body diameter (e.g., for the illustrative example, nominally 0.308 inches or 7.62 mm). The body of back bullet 340 lacks a conventional rounded or tapered nose and terminates at the front (or distally) in a full-diameter substantially planar “wad-cutter” front surface 342 symmetrically defined around the bullet's central axis, and that “wad-cutter” front surface 342 is preferably configured to snugly abut and support the flat base 328 of the coaxially aligned front bullet 320, although an inter-bullet gap (see
The method of assembling the duplex ammunition 300 of
Experiments with prototypes of the duplex cartridge system of the present invention suggest that an alternative configuration for the back bullet is useful in creating separation between the front bullet (e.g., 320) and the back bullet (e.g., 440) in the rifle's barrel (e.g., 14). Surprising test firing results are shown on the target images of
Another embodiment of the projectile assembly 400 and method are illustrated in
Referring specifically to
Back bullet 440 (see
The method of assembling the duplex ammunition 400 of
Referring now to
Gas bypass duplex projectile assembly 400 provides a surprisingly effective method for creating the inter bullet gap or bore axis longitudinal separation “IBG” 480 between the first bullet 320 and second bullet 440 within the bore (e.g., of barrel 14, as seen in
Turning now to
Back bullet 540 is fabricated or machined from a selected metal or is configured with a cladding metal jacket over a lead core. The diameter or “caliber” of the back bullet is substantially identical to the front bullet body diameter (e.g., for the illustrative example, nominally 0.308 inches or 7.62 mm). The body of back bullet 540 lacks a conventional rounded or tapered nose and terminates at the front (or distally) in a full-diameter substantially planar “wad-cutter” front surface 542 symmetrically defined around the bullet's central axis, and that “wad-cutter” front surface 542 is preferably configured to snugly abut and support the flat base 328 of the coaxially aligned front bullet 320, although an inter-bullet gap (as in
The method of assembling the duplex ammunition 500 of
Gas bypass duplex projectile assembly 500 also provides a surprisingly effective method for creating separation (e.g., “IBG” 480) between the first bullet 320 and second bullet 540 within the bore (e.g., of rifle 10). Upon firing, the cartridge's ignited powder 460 creates an expanding gas bubble which initially urges both the front and back bullets distally into the barrel's leade (not shown), where front bullet 320 engraves itself on the rifling and begins to accelerate both in its stabilizing rotation about the bullet's central axis and in its travel distally down the bore toward the muzzle. Front bullet 320 is pushed by back bullet 540 and by bypassing expanding gas from lumen 545. The gas bypass lumens or gas-ducting channels 544, 545 are in fluid communication with the distal or forward surface of back bullet 540 to direct expanding gas flowing distally into the barrel behind the distally moving front bullet 320 to pressurize the base 328 of the front bullet and force it distally down the bore while back bullet 540 is moving slightly more slowly, thereby creating the inter-bullet gap (e.g., “IBG” 480) between the distally forced accelerating front bullet 320 and the distal or front edge 542 of the slower back bullet as both bullets travel distally down the bore. This inter bullet gap (e.g., “IBG” 480) defines a captive or trapped volume of expanding gas between the front and back bullets as both travel distally down the bore and allows each bullet to accelerate and engage the barrel's rifling independently. Within the barrel (e.g., of rifle 10), each bullet 320, 540 is also independently spin stabilized by the rifling, so the rifling twist rate need not be optimized for a very, very long and heavy (e.g., 350 grains) single bullet (or abutting bullets which spin and act as one) and instead a standard twist rate stabilizes front bullet 320 separately and independently from rear bullet 540.
Tapered Ogive back bullet 640 is fabricated or machined from a selected metal or is configured with a cladding metal jacket over a lead core. The body diameter or “caliber” of the back bullet is substantially identical to the front bullet body diameter (e.g., for the illustrative example, nominally 0.308 inches or 7.62 mm). The body of back bullet 640 lacks a conventional pointed nose and terminates at the front (or distally) in a reduced-diameter substantially planar meplat front surface defining a circular surface symmetrically defined around the bullet's central axis, and that meplat front surface 642 is preferably or forced to snugly abut and support the flat base 328 of the coaxially aligned front bullet 320, although an inter-bullet gap (as seen in
The method of assembling the duplex ammunition 600 as illustrated in
During assembly of duplex cartridge 600, the front bullet's proximal flat base 328 drives against and is received against the rear bullet's substantially planar “wad-cutter” like meplat front surface 642 when the front bullet 320 is recessed into the cartridge case mouth and driven 280 thousandths of an inch into the case neck 158. Once the duplex cartridge 600 is assembled, the case neck 158 supports the rear of front bullet 320 but the front of rear bullet 640 is driven into the case enough to create an annular gas bypass lumen around the distal end 642 of front bullet 640. As shown in
Gas bypass duplex projectile assembly 600 also provides a surprisingly effective method for creating separation (e.g., “IBG” 480) between the first bullet 320 and second bullet 640 within the bore (e.g., of rifle 10). Upon firing, the cartridge's ignited powder 460 creates an expanding gas bubble which initially urges both the front and back bullets distally into the barrel's leade (not shown), where front bullet 320 engraves itself on the rifling and begins to accelerate both in its stabilizing rotation about the bullet's central axis and in its travel distally down the bore toward the muzzle. Front bullet 320 is pushed by back bullet 640 and by the expanding gas from the propellant. The annular gas bypass lumen or gas-ducting channel defined around the forward surface 642 of back bullet 640 directs expanding gas to flow distally into the barrel behind the distally moving front bullet 320 to pressurize the base 328 of the front bullet and force it distally down the bore while back bullet 640 is moving slightly more slowly, thereby creating the desired inter-bullet gap (e.g., “IBG” 480) between the distally forced accelerating front bullet 320 and the distal or front edge 642 of the slower back bullet as both bullets travel distally down the bore. This inter bullet gap (e.g., “IBG” 480) defines a captive or trapped volume of expanding gas between the front and back bullets as both travel distally down the bore and allows each bullet to accelerate and engage the barrel's rifling independently. Within the barrel (e.g., 14), each bullet 320, 640 is also independently spin stabilized by the rifling, so the rifling twist rate need not be optimized for a very, very long and heavy (e.g., 350 grains) single bullet (or abutting bullets which spin and act as one) and instead a standard twist rate stabilizes front bullet 320 separately and independently from rear bullet 640.
Back bullet 740 is fabricated or machined from a selected metal or is configured with a cladding metal jacket over a lead core. The diameter or “caliber” of the back bullet is substantially identical to the front bullet body diameter (e.g., for the illustrative example, nominally 0.308 inches or 7.62 mm). The body of back bullet 740 lacks a conventional rounded or tapered nose and terminates at the front (or distally) in a full-diameter substantially planar “wad-cutter” front surface symmetrically defined around the bullet's central axis, and that “wad-cutter” front surface is preferably configured to snugly abut and support the flat base of the coaxially aligned front bullet 320, although an inter-bullet gap (as seen in
The method of assembling the duplex ammunition 700 of
Gas bypass duplex projectile assembly 700 also provides a surprisingly effective method for creating separation (e.g., “IBG” 480) between the first bullet 320 and second bullet 540 within the bore (e.g., of rifle 10). Upon firing, the cartridge's ignited powder 460 creates an expanding gas bubble which initially urges both the front and back bullets distally into the barrel's leade (not shown), where front bullet 320 engraves itself on the rifling and begins to accelerate both in its stabilizing rotation about the bullet's central axis and in its travel distally down the bore toward the muzzle. Front bullet 320 is pushed by back bullet 740 and by expanding gas from grooves 744. The gas bypass lumens or gas-ducting channels 744 are defined in the distal or forward surface of back bullet 740 to allow expanding gas flowing distally into the barrel behind the distally moving front bullet 320, to pressurize the base 328 of the front bullet and force it distally down the bore while back bullet 740 is moving slightly more slowly, thereby creating an inter-bullet gap between the distally forced accelerating front bullet 320 and the distal or front edge of the slower back bullet 740 as both bullets travel distally down the bore. This inter bullet gap defines a captive or trapped volume of expanding gas between the front and back bullets as both travel distally down the bore and allows each bullet to accelerate and engage the barrel's rifling independently. Within the barrel (e.g., of rifle 10), each bullet 320, 740 is also independently spin stabilized by the rifling, so the rifling twist rate need not be optimized for a very, very long and heavy (e.g., 350 grains) single bullet (or abutting bullets which spin and act as one) and instead a standard twist rate stabilizes front bullet 320 separately and independently from rear bullet 740.
Finally,
Back bullet 840 is fabricated or machined from a selected metal or is configured with a cladding metal jacket over a lead core. The diameter or “caliber” of the back bullet is substantially identical to the front bullet body diameter (e.g., for the illustrative example, nominally 0.308 inches or 7.62 mm). The body of back bullet 840 lacks a conventional rounded or pointed nose and tapers slightly to terminate at the front (or distally) in a nearly full-diameter substantially planar “wad-cutter” front surface symmetrically defined around the bullet's central axis, and that “wad-cutter” front surface 842 is preferably configured to snugly abut and support the flat base of the coaxially aligned front bullet 320, although an inter-bullet gap may be defined therebetween or filled with an optional wadding disc (not shown). The body of the back bullet 840 preferably includes a sidewall segment carrying a plurality of radially spaced longitudinal grooves or vias 844 which define longitudinal lumens in fluid communication with the space behind the front bullet 320 and the propellant. Those longitudinal lumen-defining grooves 844 direct expanding gas to pass distally through around and through back bullet 840 to pressurize the space behind front bullet 320, when fired. The proximal or rearward portion of the body of the back bullet preferably has rear cylindrical sidewall segment terminating proximally in a tapered sidewall with a reduced diameter substantially planar transverse rear end to provide a boat-tail back bullet configuration.
For the gas-bypass embodiments illustrated in
The duplex projectile system ammunition assembly (e.g., 500, 600, 700 or 800) of the present invention has been configured to provide a surprising advancement in extreme impact subsonic ammunition, wherein the subsonic embodiment of the ammunition carries front and back projectiles having a combined total weight of 350 grains or more, and when fired, the front and back bullets impact in very close proximity to each other, delivering dramatic results on a target. Each duplex cartridge (e.g., in 308 Win or 7.62 NATO) will function and fully stabilize in a .308 Win.-based semi-auto platform rifle (e.g., 10) with no modifications to the rifle gas system, so subsonic duplex loads (e.g., 500, 600, 700 or 800) and supersonic loads may be fired from the same magazine with no other special considerations. For the embodiments illustrated in
The front bullet (e.g., 320) is designed to shoot smaller groups and is assigned the designation of the ammunition's “zero.” The trailing, second or back bullet (e.g., 540) is constructed as a wadcutter/full-diameter/open-tip. When the shooter or user observes groups on the target, it is easy to distinguish each bullet's impact (as described above and illustrated in
The kinetic energy delivered to the target when using the ammunition configuration of the present invention is superior. For example, comparing the cartridges described above (e.g., 500, 600, 700 or 800) to “300 Blackout” ammunition, the BLACKOUT subsonic ammunition fires a 200-grain bullet at 1075 fps to provide 471 ft-lbs of muzzle energy. BLACKOUT supersonic ammunition has a 110-grain bullet at 2300 fps which provides 823 ft-lbs of muzzle energy. The ammunition of the present invention (subsonic) provides: 350 grain total bullet mass (2 projectiles) at 1075 fps=816 ft-lbs of muzzle energy. So the subsonic 308 load of the present invention provides superior energy on target (816 ft-lbs) compared to the subsonic 300 Blackout load, and substantially equals the supersonic Blackout load's energy at 100 yards.
In the illustrated embodiments, the duplex projectile system of the present invention (e.g., 100, 200, 300, 500, 600, 700, or 800) is optimized to provide subsonic ammunition which is adapted for use in a standard rifle (e.g., 10) equipped with a suppressor (e.g., 12) or silencer. When a gas operated rifle (e.g. 10) is equipped with a suppressor (e.g., 12). The duplex projectile system of the present invention (e.g., 100, 200, 300, 500, 600, 700, or 800) creates significantly more gas port pressure than standard subsonic ammo, thus allowing standard rifles (e.g., 10) to function without requiring any gas system adjustment or requiring a substitution of louder supersonic ammunition. This benefit is important because the first and second bullets of the duplex system (e.g., 100, 200, 300, 400, 500, 600, 700, or 800) weigh more than any single bullet ever manufactured for use in a standard rifle 10. The firing of the duplex (front and rear) bullets require a higher gas pressure to reach the selected subsonic velocity desired (e.g. 1050 fps). This higher gas pressure makes it possible for an unaltered standard rifle 10 to function without adjusting the gas system. No other subsonic or volley ammunition can provide reliable gas system operation and consistent shot-to-shot subsonic accuracy in standard rifles.
Significantly, this level of performance (as illustrated in
In the prototypes developed and tested so far, the preferred velocity (e.g. 1050 fps) for the bullets in the duplex projectile system (e.g., 100, 200, 300, 400, 500, 600, 700, or 800) was generated with a propellant charge (e.g., 360) comprising 20 grains of H4350 powder when used with a Large Rifle Magnum primer. The front and back bullets of the duplex system (e.g., 100, 200, 300, 400, 500, 600, 700, or 800) can be manufactured precisely and economically by standard methods including casting, swaging or pressing metal alloy components into the desired configurations.
Having described preferred embodiments of a new and improved method, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the teachings set forth herein. It is therefore to be understood that all such variations, modifications and changes are believed to fall within the scope of the present invention as defined by the following claims.
Claims
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.
Type: Application
Filed: Feb 28, 2017
Publication Date: Sep 28, 2017
Inventors: G. David TUBB (Canadian, TX), George Wyatt Tubb (San Antonio, TX)
Application Number: 15/445,792