Abstract:
A high-pressure fixed munition for a low-pressure launching system having a cylindrical body with a centrally located bore is provided. The bore of the munition has a reduced diameter on the charge end in which a primer charge is positioned. The bore is filled above the primer charge with a propellant and above the propellant with a payload. The payload may include multiple buckshot pellets, frangible buckshot pellets, tear gas, multiple slugs, frangible slugs, paint balls, rubber pellets, bean bags, or the like. The munition may also include a pressure disk between the propellant and the payload, and tactile ridges or on the outside surface of the munition body or be of a specific color for purposes of identification of the payload.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority from Provisional Application Ser. No. 60/541,935, filed Feb. 6, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to munitions and more specifically munitions designed for low-pressure weapon systems.  
       BACKGROUND OF THE INVENTION  
       [0003]     Beginning in the 1950s, a family of 40 mm grenade launchers was developed to assist soldiers to cover the area between the longest range of the hand grenade (30-40 yards) and the middle range of the 60 mm mortar (300-400 yards). The family of 40 mm grenade launchers includes: the M79, the M203 and the M203a. Each of the 40 mm grenade launchers fires various types of 40 mm cartridges including: high explosive (“HE”) rounds, projectile practice rounds, chemical rounds, buckshot rounds and pyrotechnic signal and spotting rounds.  
         [0004]     The 40 mm M79 grenade launcher resembles a large bore, single aluminum barrel, sawn off shotgun. The M79 grenade launcher was developed in the 1950s and was first delivered to the US Army in 1961.  
         [0005]     The 40 mm M203 grenade launcher was developed to attach to an existing M-16 rifle and M-4 carbine. It consists of a 10-inch long aluminum barrel and a receiver clamped underneath an M-16 barrel. A variation of the M203 is the M203a, which consists of an 8-inch long aluminum barrel and a receiver clamped underneath a M-4 carbine. The working pressure of each of the M79/M203/M203a is 3000 psi.  
         [0006]     Because the HE rounds require an arming delay of an internal fuze device, and because of the blast radius associated with the high explosive, the HE round is not effective at close ranges.  
         [0007]     To provide close range potential for an M79, M203 or M203a grenade launcher, a shotgun shell type round was developed, known as an XM576. The XM576 includes 20 No. 4 buckshot pellets (each 0.24-inch in diameter) that leave the M79/M203/M203a muzzle at only 885 feet per second. Unfortunately, the XM576 has not performed as hoped either by the military or by law enforcement.  
         [0008]     In another effort to improve the close range effectiveness of the M79/M203/M203a family of grenade launchers, a 12-gauge sub-caliber device was developed and was issued to service personnel in Vietnam on an experimental basis. The sub-caliber device consisted of a steel rim and liner with a spring-loaded extractor inside a 40 mm plastic bushing. The device was about 9-inches long and would accept any commercial 12-gauge buckshot load. Other such devices have been constructed in lengths of 5-inches overall. Unfortunately, neither the XM576 nor the sub-caliber devices can provide satisfactory shot patterns or velocity at ranges beyond approximately 10 yards.  
         [0009]     What is needed is a device that can be used in existing M79/M203/M203a grenade launchers, or other sizes of low pressure launching systems, to provide a close quarter battle load and at the same time, overcome the problems that exist with the XM576 round and sub-caliber adapters.  
       SUMMARY  
       [0010]     A high-pressure fixed munition for a low-pressure launching system having a cylindrical body with a centrally located bore is provided. The bore of the munition has a reduced diameter on the charge end in which a primer charge is positioned. The bore is filled above the primer charge with a propellant and above the propellant with a payload. The payload may include multiple buckshot pellets, frangible buckshot pellets, tear gas, multiple slugs, frangible slugs, paint balls, rubber pellets, bean bags, or the like. The munition may also include a pressure disk between the propellant and the payload, and tactile ridges or on the outside surface of the munition body or be of a specific color for purposes of identification of the payload.  
         [0011]     Closed cell foam can be inserted in the top of the high-pressure fixed munition to seal off the contents from mud, sand, water or other debris.  
         [0012]     The resulting inventive high-pressure fixed munition provides an improved muzzle velocity, range and shot pattern in comparison to conventional munitions used with low pressure launching systems. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a cross section view of a 40 mm XM576 multiple projectile round.  
         [0014]      FIG. 2  is an outside view of a 40 mm sub caliber adapter including a cross section view of a conventional 12-gauge shotgun shell.  
         [0015]      FIG. 3  shows an M203 grenade launcher attached to an M-16 Rifle.  
         [0016]      FIG. 3A  shows the inventive high-pressure fixed munition inside of the M203 of  FIG. 3 .  
         [0017]      FIG. 4  is an outside view of an M79 grenade launcher.  
         [0018]      FIG. 5  is an outside view of the inventive high-pressure fixed munition.  
         [0019]      FIG. 6  is a section view of the inventive high-pressure fixed munition shown in  FIG. 5  including twenty-five frangible “00” buckshot pellets.  
         [0020]      FIG. 6A  is a section view of the inventive high-pressure fixed munition shown in  FIG. 5  including twenty “00” buckshot pellets.  
         [0021]      FIG. 6B  is a section view of the inventive high-pressure fixed munition shown in  FIG. 5  including three frangible slugs.  
         [0022]      FIG. 7  is an assembly view of the inventive high-pressure fixed munition shown in  FIG. 5 .  
         [0023]      FIG. 8  is a sectional view of the inventive high-pressure fixed munition with a shotgun primer.  
         [0024]      FIG. 9  is a detail assembly view of the primer and base of the inventive high-pressure fixed munition of  FIG. 8 .  
         [0025]      FIG. 10  is a detail partial sectional view of the inventive high-pressure fixed munition shown in  FIG. 8  showing the choke feature.  
     
    
     DETAILED DESCRIPTION  
       [0026]     The following table, viewed together with the enclosed figures and detailed description, is provided to understand clearly a preferred embodiment of the invention:  
                                                   Number:   Description:                           P1   XM576 Multiple Projectile Round           12   Primer           14   Propellant           14a   Brass Powder Charge Cup           16   Vent Holes           18   Low Pressure Chamber           20   Sabot           22   Pellets           P2   Sub-caliber Adapter           32   Primer           34   Propellant           35   12-Gauge Shotgun Shell           36   Wad           37   Shot Cup           39   Base Surface           42   Pellets #4 Buckshot           44   Bore           B   M16 Carbine           B1   M203 Grenade Launcher           B1A   M203 Grenade Launcher Barrel           C   M79 Grenade Launcher           C1   M79 Grenade Launcher Barrel           46   Breach Face           A   High Pressure Fixed Munition           50   Raised Ridges           52   Body of High-Pressure Fixed Munition           54   Primer           55   Bore           56   Shell Casing           57   Small Bore for Shell Casing           58   Propellant           58a   Propellant in shell casing           59   Lower Flat of Large Bore           60   Burst Disk           62   Wad           64   Pellets “00” Frangible Buckshot           64a   Pellets “00” Buckshot           64b   Frangible Slugs           65   Shot cup           66   Leading Taper           67   Base Surface of High-Pressure Fixed Munition           68   Foam           68a   Upper Large Diameter           68b   Lower Large Diameter           70   Shotgun Primer           72   Shotgun Primer Bore           74   Choked Taper           74a   Choked Taper Angle                      
 
         [0027]     Referring now to  FIG. 1 , an existing prior art XM576 round, designated generally as P 1 , is shown. The XM576 includes a primer  12  that ignites the propellant  14 , which is enclosed within a brass powder charge cup  14   a . The ignited propellant  14  develops a pressure of 35,000 psi that ruptures the brass charge cup  14   a  at the vent holes  16 . The gases that enter the low-pressure chamber  18  from the vent holes  16  are at a pressure of approximately 3000 psi, which propel the pellets  22  toward the intended target.  
         [0028]     In  FIG. 2 , a prior art sub-caliber adapter, generally designated as P 2 , is shown. The sub-caliber adapter is slightly less than 40 mm on the outside diameter so that it can be used in existing M79/M203/M203a grenade launchers, which have a 40 mm diameter barrel (See  FIGS. 3, 3A  and  4 ). It includes a straight through bore  44  that is sized to accommodate a conventional 12-gauge shotgun shell  35 . The shotgun shell  35  includes a primer  32  that ignites propellant  34 , which expands to launch the pellets  42 . The pellets  42  are held together during launching with the wad  36  and wad cup  37 .  
         [0029]     Both the XM576 (P 1 ) and the sub-caliber adapter (P 2 ) are designed to be fired from an M79 grenade launcher, designated as C in  FIG. 4 , or from an M203 grenade launcher, designated as B 1  in  FIG. 3 . The M203 grenade launcher B 1  is shown mounted to an M-16 carbine B in  FIG. 3 . Both the XM576 and the sub-caliber adapter may also be fired from an M203a grenade launcher, which is a shorter version of the M203 grenade launcher (B 1 ), which is mounted onto an M-4 (not shown).  
         [0030]     The inventive high-pressure fixed munition is designated in  FIG. 5  generally as A. The high-pressure fixed munition A is 40 mm on the largest outside diameter and may be fired from the M79 grenade launcher (C) shown in  FIG. 4 , from the M203 grenade launcher (B 1 ) shown in  FIG. 3 , or from an M203a grenade launcher (not shown). All of the grenade launchers M79/M203/M203 have a receiving chamber and barrel diameter of 40 mm, which is just slightly greater than the 1.605 inch outside diameter of the high-pressure fixed munition A. The base surface  67  of the high-pressure munition A allows a high internal operating pressure to be spread across the entire base surface  67  to minimize stress on the breach face  46  (shown in  FIG. 3A ). The base surface  39  of the sub-caliber adapter P 2  is limited in surface area and an increase in pressure could damage the breach face  46  of the M79/M203/M203a grenade launcher or the aluminum barrel.  
         [0031]     The upper large diameter  68   a  and the lower large diameter  68   b  center the high-pressure munition A within the chamber of the barrel B 1   a  and C 1  ( FIGS. 3, 3A  and  4 ).  
         [0032]     A conventional .38 Smith and Wesson cartridge case  56  is inserted into the small bore  57  of the high-pressure munition A as best seen in  FIG. 6 . A primer  54  is inserted into the base of the .38 Smith and Wesson cartridge case  56 . Alternative cartridge cases may also be used. Propellant  58  is inserted from the top of the high-pressure munition A to provide the desired pressure for the load used.  
         [0033]     An alternative embodiment shown in  FIGS. 8 and 9  includes a shotgun primer  70  that ignites the propellant  58  to discharge the buckshot  64   a , or other desired payload. A preferred shotgun primer  70  is the Federal 209A, but other primers may also be used. The shotgun primer  70  fits into the shotgun primer bore  72 . The shotgun primer  70  may either be flush with the base surface  67  of the high-pressure fixed munition A or may be raised slightly above the base surface  67  as shown in  FIG. 8 . It is contemplated that any primer that provides the necessary ignition for the propellant may also be used in place of the shotgun primer  70 .  
         [0034]     An optional burst disk  60  is inserted above the propellant  58 . The burst disk  60  seals off propellant charge from the base of the high-pressure munition A, retaining the propellant  58  sufficient for efficient power combustion. Because the propellant  58  bears against the burst disk  60  and does not use an expansion chamber, the pressure front from the propellant gasses is prevented from distorting the body  52  of the high-pressure munition A.  
         [0035]     The burning characteristics of the propellant  58  can be adjusted to allow the use of frangible projectiles, which can distort and fracture under pressure.  
         [0036]     A wad  62  is inserted above the burst disk  60 . The wad  62  includes a shot cup portion  65 , into which projectiles are inserted. Because of the large volume available in the bore  55  of the high-pressure fixed munition A relative to the volume available in a conventional shotgun shell  35  shown with the prior art sub-caliber adapter P 2  in  FIG. 2 , a greater amount of projectiles can be used. In  FIG. 6 , twenty-five “00” frangible buckshot pellets are shown; in  FIG. 6A , twenty “00” buckshot pellets are shown; and in  FIG. 6B , three frangible slugs are shown. The loads that can be used in the high-pressure fixed munition A are not limited to those shown and may also include other desired loads and varieties of projectiles. In place of conventional projectiles, paint balls may also be shot from the high-pressure fixed munition A. Paint ball rounds can be used for training or marking purposes. Other projectiles, such as rubber pellets, cloth stun bags, or batons can also be used.  
         [0037]     It should be appreciated that the bore  55  can be enlarged for example, when paint balls are to be used, and can be otherwise changed in size as desired.  
         [0038]     The exit of the bore  55  can be reduced in diameter to form a choked taper  74  ( FIG. 10 ) of desired configuration to modify the resulting spread pattern of the projectile pellets  64 ,  64   a .  FIG. 10  also illustrated the choke angle  74   a  that defines the taper of the choke  74 . The barrels B 1 , C 1  cannot be choked to adjust the spread pattern because such a restriction would prevent the sabot  20  from exiting the bore of the launcher. This is another significant advantage of the high-pressure fixed munition.  
         [0039]     The body  52  of the high-pressure fixed munition A is typically constructed of thermoplastic nylon 6/12, but can also be constructed of glass filled nylon, other desired polymer or a desired metal, such as aluminum. Other metallic materials or a combination of different materials, including, but not limited to polymer with metallic construction are also contemplated.  
         [0040]     The high-pressure fixed munition A may be used as an expendable munition or may be reloaded. The body  52  material may be reused many times if desired.  
         [0041]     The pressure containment properties of the body  52  allow the high-pressure fixed munition A to retain the high pressure of the gasses from the propellant  58  thereby allowing the use of the high-pressure fixed munition A in the M79/M203/M203a grenade launchers, which were originally designed for use with low pressure munitions. The pressure developed in the high-pressure fixed munition A is 12,000-15,000 psi, which exceeds the allowable working pressure of 3,000 of the M79/M203/M203a grenade launchers. The reason the high-pressure fixed munition can be operated safely in the low-pressure grenade launchers is because the bore  55  of the high-pressure fixed munition A acts as the barrel, effectively replacing the barrel B 1   a  of the M203 ( FIG. 3 ) and the barrel C 1  of the M79 ( FIG. 4 ). The high pressures developed in the high-pressure fixed munition are exposed to the bore  55  of the body  52  of the high-pressure fixed munition and they are not exposed to the inner bore of the barrels of the low pressure grenade launchers.  
         [0042]     Closed cell foam  68  may be inserted in the top of the high-pressure fixed munition A to seal off the contents thereof from mud, sand, water or other debris. Multi-purpose latex foam, such as that manufactured by DAP®, may be used but other foams can also be used. The important characteristics include: providing a water barrier, low density, high toughness and resilience. Biodegradable, closed cell foam can also be used to allow the high-pressure fixed munition A to be environmentally compatible.  
         [0043]     Raised ridges  50  ( FIGS. 5, 6 ,  6 A,  6 B and  7 ) on the outside of the body  52  are designed to allow the identification of the loading of the high-pressure fixed munition A in any light condition. For example, there can be a single raised ridge  50  for high-pressure fixed munition A containing “00” frangible buckshot pellets, two raised ridges  50  for “00” buckshot and three raised ridges  50  for frangible slugs. The different loadings of the high-pressure fixed munition A may also be identified by different colors. The raised ridges  50  also assist in centering the high-pressure munition A in the bore of the weapon.  
         [0044]     As indicated by the following tables, the performance of the high-pressure fixed munition A is far superior to the performance of either the XM576 (P 1 ) or the sub-caliber adapter (P 2 ).  
                                                     Comparison of Performance between High-Pressure       Fixed Munition to M576 and Sub-Caliber Adapter       High-Pressure Fixed Munition (A)*                        25-“00”               3-12 gauge   20-“00”   frangible   26-#1           frangible   buckshot   buckshot   buckshot           slugs (1075   (1075   (1075   (1075       Load   grains)   grains)   grains)   grains)               Muzzle Velocity   1250   1250   1250   1250       (ft/sec)       Range (yards)    65    65    65    65       Dispersion   As   As   As   As       (spread pattern)   desired**   desired**   desired**   desired**       at 25 yards                 *Muzzle velocities are based on estimate from penetration rates measured at 10 feet and 30 feet ranges.            **Dispersion (spread pattern) is adjustable by restricting the exit bore 55 (choking) of the high-pressure fixed munition.             
 
         [0045]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                   
               
               
                 XM576 (P1) 
               
             
          
           
               
                   
                   
                 20-#4 buckshot 
                 27-#4 buckshot 
               
               
                   
                 Load 
                 (380 grains) 
                 (513 grains) 
               
               
                   
                   
               
             
          
           
               
                   
                 Muzzle Velocity (ft/sec) 
                 885 
                 850 
               
               
                   
                 Range (yards) 
                 10 
                 10 
               
               
                   
                 Dispersion (spread 
                 36 
                 36 
               
               
                   
                 pattern) at 25 yards 
               
               
                   
                 (Inches in diameter) 
               
               
                   
                   
               
             
          
         
       
     
         [0046]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                   
               
               
                   
               
               
                 Sub-Caliber Adapter (P2) 
               
             
          
           
               
                   
                 Load 
                 31/2 shell with 12-“00” buckshot 
               
               
                   
                   
               
             
          
           
               
                   
                 Muzzle Velocity (ft/sec) 
                 850 
               
               
                   
                 Range (yards) 
                 10 
               
               
                   
                   
               
             
          
         
       
     
         [0047]     The high-pressure fixed munition A is a more effective munition than either the XM576 (P 1 ) or the sub-caliber adapter (P 2 ). The high-pressure fixed munition A has a higher muzzle velocity than both the XM576 (P 1 ) and the sub-caliber adapter (P 2 ), even though the high-pressure fixed munition A fires projectile loads that are heavier than those fired in the XM576 (P 1 ) and the sub-caliber adapter (P 2 ). The larger pressures that are developed in the high-pressure fixed munition A results in the higher velocities and also provides increased ranges of the projectiles. Furthermore, loads of 18 or 20 pellets of “00” buckshot or 25 pellets of frangible “00” buckshot shot from the high-pressure fixed munition result in a shot pattern of approximately 4″ at 10 feet and 8″ at 30 feet. It is believed that the tight shot pattern is the result of a pressure front that travels in front of the propellant and that surrounds the pellet load as it travels away from the barrel B 1 , B 1 A. The pressure front tends to contain the pellet load in a desirable, tight pattern.  
         [0048]     Even though the high-pressure fixed munition A develops pressures exit pressures that are 12,000-15,000 psi, the high pressures in combination with the large loads do not create large recoils to the shooter. Instead, it is believed that the large mass of the weapons in which the high-pressure fixed munition A are fired absorbs the energy and resists transferring the recoil inertia back to the shooter. The lack of heavy recoil is an important feature with the high-pressure fixed munition A because it reduces the tendency for a shooter to flinch, in anticipation of a large recoil, thereby losing his or her concentration and accuracy.  
         [0049]     The length of the barrel C 1  on the M79 (C) ( FIG. 4 ) is 14 inches. The length of the barrel B 1  on the M203 ( FIG. 3 ) is 10 inches. On the M203a (not shown), the length of the barrel is only 8 inches. When either the XM576 (P 1 ) or the sub-caliber adapter (P 2 ) are fired through different length barrels, the performance varies. The resulting spread can change as well as the velocity, range and accuracy. The muzzle velocity, range and accuracy of projectiles fired from the high-pressure fixed munition A are independent of the length of the barrel. It should be appreciated that the invention disclosed herein may also be used in varying sizes of launching systems other than the 40 mm sized systems.  
         [0050]     Because many varying and different embodiments may be made within the scope of the inventive concept herein taught and claimed, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.