Abstract:
Embodiments of the present invention relate generally to cartridges and modifications for an M16/AR15 rifle. In one embodiment, a modified M16/AR15 rifle or carbine includes a bolt having a maximum outside diameter greater than that of a standard M16/AR15 bolt; and a bolt extractor pivoted to the bolt. The bolt and the bolt extractor are operable to: transport a cartridge from a magazine to a barrel, and eject a spent cartridge from the barrel. The rifle or carbine further includes a barrel extension configured to receive the bolt; a standard M16/AR15 upper receiver coupled to the barrel extension; a standard M16/AR15 lower receiver coupled to the upper receiver.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the present invention relate generally to cartridges and modifications for an M16/AR15 rifle. 
         [0003]    2. Description of the Related Art 
         [0004]    Domestic Law Enforcement Needs 
         [0005]    Most domestic law enforcement agencies in the United States utilize the AR15/M16 rifle platform in the course of their daily duties, as patrol officers out on the street; it is often referred to as a “patrol carbine” and is carried by individual officers. These rifles are also used by SWAT teams for room entry or close quarter&#39;s battle (CQB) for close in shooting, and are used by some departments as short range sniper rifles. The reasons for the selection of this rifle platform are that they are readily available in many configurations and are fairly reasonably priced to Law Enforcement agencies, the AR15&#39;s weight and size are also attractive features of the AR15 as they are easily operable by large men and smaller stature women. The limiting factor is the cartridge that it fires, the 223 Remington, most commonly using a 55 grain bullet. Domestic law enforcement is not held to the military restriction of using full metal jacket projectiles and therefore can choose from a wide variety of available bullet styles and designs, which makes the 223 Remington more effective. 
         [0006]    Even with the proper selection of ammunition, the 223 Remington is still substandard for most law enforcement applications and has a well known reputation for “over penetration” with its small-fast bullet. This can result in extremely dangerous situations for patrol officers working in a built up urban environment. The small weight or mass of the bullet makes it less effective and more prone to deflection on vehicles when engaged by police, especially when engaging thick windshield glass. Although there are a few “alternate” cartridges available that will function in the AR15 rifle, they do not offer enough of an improvement over the existing .223 Remington cartridge chambering to justify the cost in switching over to them, mainly cost and availability of ammunition and magazines. Thus the agencies are limited on their choices of cartridge choices if they maintain the AR15/M16 rifle platform as their weapon of choice. 
         [0007]    The other choice for law enforcement agencies is the larger and more costly AR15 “style” rifle made by various companies that fire the .308 Winchester cartridge. The .308 Winchester is a powerful cartridge and offers a substantial improvement over the much smaller .223 Remington chambering. Most police sniper rifles are chambered in the .308 Winchester and are bolt action guns, which do not allow for quick follow up shots if needed. 
         [0008]    When quick follow up shots are required the larger AR15 style rifles are sometimes used, they are heavier and have more recoil than the smaller rifles, but deliver ample firepower when needed. These heavier and larger rifles are not the preferred option for SWAT teams for use in room entry and building clearing operations because the power of the 308 Winchester is too much for inside building operations, due to muzzle blast, recoil, and over penetration. 
         [0009]    These two calibers represent not only the two most popular calibers used in law enforcement but are the two extremes, with the 223 Remington not providing enough performance or power and the 308 Winchester providing too much or excessive power. 
         [0010]    United States Military Needs 
         [0011]    The existing standard cartridge or chambering for the military&#39;s M16 rifle is the .223 Remington or 5.56 mm NATO (military designation) cartridge. It fires a .224 caliber bullet weighing 62 grains in the military issue M855 ammunition. Bullets weighing as much as 77 grains are currently in use by the US military to increase the performance of the 5.56 mm NATO cartridge and have increased the terminal performance of the cartridge, but its terminal effects are still less than desirable for what is considered an adequate combat cartridge. The shortcomings in the performance of the 5.56 mm NATO cartridge are well documented in current and past military conflicts, and the cartridge&#39;s ineffectiveness is more pronounced when the enemy combatants are under the influence of drugs that affect the central nervous system. 
         [0012]    An alternative for heavier machine guns is the .308 or 7.62 mm caliber bullet. The most common military caliber utilizing the .308 or 7.62 mm caliber bullet is the 308 Winchester or 7.62 mm NATO cartridge. The performance of the 7.62 NATO is also well documented in combat and is known for its increased stopping power. The U.S. M14 rifle fires the 7.62 mm NATO cartridge as does the U.S. M240 machinegun, as well as several aircraft mounted machineguns and the mini-gun. The AK47 also utilizes a 7.62 mm bullet. 
         [0013]    What is needed is a cartridge that will provide improved stopping power without over penetrating, and is compatible with the standard size M16/AR15 rifle platform. 
       SUMMARY OF THE INVENTION 
       [0014]    Embodiments of the present invention relate generally to cartridges and modifications for an M16/AR15 rifle. In one embodiment, a modified M16/AR15 rifle or carbine includes a bolt having a maximum outside diameter greater than that of a standard M16/AR15 bolt; and a bolt extractor pivoted to the bolt. The bolt and the bolt extractor are operable to: transport a cartridge from a magazine to a barrel, and eject a spent cartridge from the barrel. The rifle or carbine further includes a barrel extension configured to receive the bolt; a standard M16/AR15 upper receiver coupled to the barrel extension; a standard M16/AR15 lower receiver coupled to the upper receiver. 
         [0015]    In another embodiment, a cartridge includes a bullet having a diameter greater than or equal to 0.224 inch; and a case having a case head diameter greater than or equal to 0.45 inch. A length of the cartridge is substantially equal to 2.26 inches. 
         [0016]    In another embodiment, a firearm includes a barrel. The firearm further includes a bolt operable to transport a cartridge from a magazine to the barrel and eject the spent cartridge from the barrel. The firearm further includes a spring biasing the bolt toward the barrel and a piston system in fluid communication with the barrel. The piston system includes a body and a piston disposed in the body and operable to move the bolt away from the barrel in response to firing of the cartridge and force exhaust gas from the body and into the barrel in response to the spring returning the bolt to the barrel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0018]      FIGS. 1A-1C  illustrate cartridges, according to embodiments of the present invention. 
           [0019]      FIG. 2  is an exploded assembly of a bolt, bolt extractor, and barrel extension usable with the cartridges of  FIGS. 1A-1C . 
           [0020]      FIGS. 3A-3E  illustrate details of the bolt of  FIG. 2 . 
           [0021]      FIGS. 4A-4E  illustrate details of the bolt extractor of  FIG. 2 . 
           [0022]      FIGS. 5A-5D  illustrate details of the barrel extension of  FIG. 2 . 
           [0023]      FIGS. 6A-6G  illustrate details of a magazine usable with the cartridges of  FIGS. 1A-1C . 
           [0024]      FIGS. 7A-7D  illustrate details of a bolt usable with the cartridges of  FIGS. 1A-1C  and a modified gas piston system, according to another embodiment of the present invention. 
           [0025]      FIG. 8  is a cross section of a gas piston system, according to another embodiment of the present invention. 
           [0026]      FIG. 9  is an exploded assembly of a prior art M16/AR15. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIGS. 1A-1C  illustrate cartridges, according to embodiments of the present invention. 
         [0028]    The 308 ERC was designed to maximize the performance of the AR15/M16 rifle, give it more stopping or incapacitation power and increase its performance in self defense, law enforcement, and military combat applications. The 308 ERC is based on the .308 Winchester or 7.62 mm NATO cartridge, utilizes the 308 caliber bullet, and is designed to operate in the existing standard issue sized AR15/M16 rifle platform. 
         [0029]    Cartridge Details; 
         [0030]    Case head diameter; 0.473″ inches (a 25% increase over the 223 Remington/5.56 NATO) 
         [0031]    NL is an abbreviation for neck length. NW is an abbreviation for neck wall. COL is an abbreviation for cartridge overall length 
         [0032]    Powder capacity; 52% increase over the 223 Remington/5.56 NATO &amp; 18% less than the 308 Winchester 
         [0033]    Projected design performance data; 
         [0034]    Bullet weight: 135-140 grains 
         [0035]    Muzzle velocity: 2650 feet per second (fps) (16″ barreled AR15/M16 carbine) 
         [0036]    Muzzle energy: 2106 foot pounds 
         [0037]    Muzzle energy increase: 82% (compared to military current issue M855 62 grain FMJBTWC@2900 fps fired from a 16″ barreled AR15/M16 carbine) 
         [0038]      FIG. 2  is an exploded assembly of a bolt, bolt extractor, and barrel extension usable with the cartridges of  FIGS. 1A-1C . Although the cartridge is designed to operate in the AR15/M16 platform, the following design changes were required (in addition to modification of the barrel); 
         [0039]    204-ERC redesigned bolt 
         [0040]    206-ERC redesigned bolt extractor 
         [0041]    202-ERC redesigned barrel extension 
         [0042]    FIG.  6 A- 6 G-ERC redesigned magazines, 25 round capacity 
         [0043]    Additional ERC cartridges: 
         [0044]    Although any of these cartridges utilizing the ERC case can be used for self defense or law enforcement applications, their projected use is listed below; 
         [0045]    224 caliber/5.7 mm—varmint hunting, rifle competition 
         [0046]    243 caliber/6 mm—varmint hunting, rifle competition 
         [0047]    264 caliber/6.5 mm—varmint hunting, rifle competition 
         [0048]    270 caliber/6.8 mm—military, law enforcement, hunting 
         [0049]    308 caliber/7.62 mm—military, law enforcement, hunting 
         [0050]    338 caliber/8.6 mm—military, law enforcement, hunting 
         [0051]    440 KINETIC—military, law enforcement, door &amp; wall breeching, hunting 
         [0052]    440 ENTRY (buckshot)—military, law enforcement, door &amp; wall breeching, room entry (CQB), hunting. The barrel may be smooth bore or rifled for the 440 ENTRY. 
         [0053]    The bullets may have hollow points and may have full metal jackets or be semi-jacketed (lead tip). 
         [0054]      FIGS. 7A-7D  illustrate details of a bolt usable with the cartridges of  FIGS. 1A-1C  and a modified gas piston system (see  FIG. 8 ), according to another embodiment of the present invention. All dimensions are in inches. 
         [0055]      FIG. 8  is a cross section of a gas piston system  800 , according to another embodiment of the present invention. 
         [0056]    The use of gas piston systems in weapons to cycle the action is used in weapons such as the Russian AK 47 (1947), the U.S M1 Garand (1939) and the U.S. M14 (1957). There are as many as five gas piston systems currently manufactured for the AR15 rifle by various companies. They use a gas piston actuated by “tapped gas” from the fired cartridge via a small hole or “gas port” in the barrel, the expanding gas forces the piston to move. As such, the gas from a fired cartridge is utilized to cycle the action and load the next cartridge. The expanding gas from the fired cartridge, once utilized to cycle the piston, is then vented out of the gas manifold at the end of the piston operating stroke before the piston returns to the starting position. 
         [0057]    The standard design gas system used in AR15 and M16 rifles utilizes a “direct gas impingement system” which directs expanding gas from the fired cartridge out of the barrel through a “gas port” or hole in the barrel. The expanding “tapped gas” is then directed through a “gas tube” which “directs” the gas back into the upper receiver. The gas then enters the “bolt carrier key” forcing the carrier to the rear and unlocking the bolt of the rifle, beginning the cycling process. 
         [0058]    The gas piston system  800  may include a barrel  805 , a piston/rod assembly  810 , a gas block  815 , and a gas block cap  820 . The gas block  815  may have a bore formed therethrough, may be disposed around the barrel  805 , and secured to the barrel  805  with fasteners (not shown), such as screws or pins. The gas block  815  may have a piston chamber formed therein. A piston  810   p  of the piston/rod assembly  810  may be disposed in the piston chamber. The piston  810   p  may divide the chamber into an air sub-chamber and an exhaust sub-chamber. The piston  810   p  may be longitudinally coupled to a rod  810   r  of the piston/rod assembly  810 , such as by being formed integrally therewith or welded thereto. The piston  810   p  may include an array of carbon grooves (not shown) formed around an outer surface thereof. The cap  820  may be coupled to the gas block  815  by a threaded connection. The rod  810   r  may extend through a bore formed through the cap  820 . The cap may have one or more ports  820   p  formed therethrough and providing air communication between air sub-chamber and the atmosphere. The gas block  815  may have a channel  815   c  formed between the chamber and the bore and providing fluid communication between the exhaust sub-chamber and a port  805   p  formed through a wall of the barrel  805 . The port  805   p  may provide fluid communication between a bore  805   b  of the barrel  805  and the channel  815   c.  The bore  805   b  barrel may be rifled (not shown) to impart rotation to a bullet (not shown) fired therethrough. The piston  810   p  may include a recess formed therein in fluid communication with the exhaust sub-chamber. One or more ports  810   h  may be formed through a wall of the piston  810   p  and may provide fluid communication between the channel  815   c  and the piston recess. 
         [0059]    In operation, as the bullet passes the gas port  805   p  in the barrel  805 , and before the bullet exits the barrel, the exhaust sub-chamber becomes pressurized from the expanding gas of the fired cartridge via (port  805   p,  channel  815   c,  and ports  810   h ). The pressurized exhaust gas forces the piston  810   p  to the rear of the piston chamber or “full stroke” position. The operating rod  810   r  pushes on the bolt carrier key (see  FIG. 9 ), which then moves the bolt carrier to the rear, unlocking the bolt and cycling the rifles action. As the bolt carrier is forced to the rear, it compresses the rifles main operating spring (buffer spring). Air in the air sub-chamber is vented to the atmosphere via the ports  820   p.    
         [0060]    Once the bullet has exited the muzzle or flash suppressor and the pressure in the rifle bore decreases, the piston/rod assembly  810  is pushed back to the forward or “resting position” by the expanding buffer spring. As the bolt and bolt carrier continue forward, the bolt carrier is returned all the way to the forward position, locking the bolt. The residual gas in the piston chamber is exhausted back into the barrel through the gas channel  815   c  and gas port  805   p.  The firing sequence is now complete, and the rifle is now ready to fire again. The gas piston system  800  keeps exhaust gas near the front end of the gun and in the barrel instead of discharging the gas into the upper receiver as the conventional M16/AR15 gas impingement system does. 
         [0061]    Alternatively, the gas piston system may be incorporated into the front sight. Alternatively, the ports  810   h  may be omitted and the channel  815   c  may be in direct fluid communication with the piston recess. Alternatively, the ports  810   h  may be omitted, a primary channel may be in direct fluid communication with the piston recess and an auxiliary gas channel may be in fluid communication with the exhaust sub-chamber when the piston is in the full stroke position, thereby aiding venting of the exhaust gas into the barrel and accelerating return of the piston to the at-rest position. 
         [0062]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.