Subcaliber device/blank firing adaptor for blowback operated or recoil operated weapons

Information

  • Patent Grant
  • 6202533
  • Patent Number
    6,202,533
  • Date Filed
    Monday, July 26, 1999
    24 years ago
  • Date Issued
    Tuesday, March 20, 2001
    23 years ago
Abstract
The bolt of a blowback operated weapon is driven rearward by multiplying the area acted upon by pressurized gas generated by a subcaliber bulleted cartridge or a blank cartridge fired in a subcaliber barrel inserted into the weapon barrel and attached to the weapon barrel muzzle.
Description




BACKGROUND OF INVENTION




This invention is related to BLANK FIRING ADAPTOR, U.S. Pat. No. 5,438,907 by George Reynolds and John Miller, but is equipped with a subcaliber barrel instead of a spigot, employs gas pressure multiplier system and fires bulleted cartridges or blanks.




Medium caliber automatic weapons such as the Mk19, 40 mm machinegun used by U.S. military forces require relatively expensive training ammunition because of the relatively large size of the ammunition used plus the fact that the Mk 19 is a machinegun. It is estimated there are 300,000 Mk 19's in active use in the U.S. military services. It is conservatively estimated that each gun is fired 100,000 rounds in training during the life of the weapon. Conventional training rounds cost approximately $15 each, resulting in a life cycle training cost for ammunition of $450 billion. Thus, the cost of adequate training is very high for this very effective weapon. Subcaliber devices which provide realistic training are well known for use in most small arms weapons, but until the present, none have been suitable for use with the Mk19 and similar weapons.




SUMMARY OF PRESENT INVENTION




The present invention provides for realistic training by firing relatively inexpensive subcaliber cartridges or blanks in reloadable adaptors. With the cost of the subcaliber device/blank firing adaptor at, say $500 each, the cost of the adaptor cases at $5 each and the cost of the subcaliber cartridge or blank cartridge at 25 cents each, the life cycle cost for firing 100,000 subcaliber rounds through 300,000 Mk19's is approximately $9.1 billion, as compared with $450 billion dollars with full caliber training rounds. Use of the subcaliber device will result in a 98% cost reduction for training ammunition compared to using the least expensive full caliber training rounds.




The subcaliber device/blank firing adaptor powers a blowback or recoil operated weapon so the weapon will function in normal automatic fire. All loading, firing, safety, and stoppage procedures normally performed by the gun crew are employed when using the sibcaliber device/blank firing adaptor.




Firing with the subcaliber device/blank firing adaptor approximates the feel and noise of firing full caliber service ammunition. The trajectory of the subcaliber projectile nearly duplicates that of fill caliber service ammunition. This closely matching trajectory is especially valuable when using subcaliber tracer projectiles so the soldier can become very familiar with the characteristics of time of flight and trajectory arc of service rounds while firing inexpensive subcaliber rounds.




The cartridge case adaptor which contains the subcaliber cartridge or blank cartridge is easily and rapidly reloadable by soldiers training in the field. Reloading is accomplished using a simple, hand operated fixture which is not part of this patent. Installation of the subcaliber device/blank firing adaptor requires no special tools and is performed by the gun crew in the field, requiring less than five minutes in the case of the Mk19 machinegun. All subcaliber device/blank adaptor components are low technology, require no exotic materials, and are inexpensive to manufacture. The blank firing adaptor uses standard, commonly issued conventional rifle/machinegun blanks.




In the three subcaliber device embodiments of the invention three different methods are used to multiply the force of the propellant gas above the straight blowback force of the projected area of the base of the projectile. In the blank firing adaptor embodiment, gas is trapped by a vented muzzle disc at the front of the subcaliber barrel to retain pressurized gas to apply sufficient force to operate the weapon.




In the first embodiment, instead of reaction of the propellant gas being only against the projectile, part of the reaction is transmitted from a primary booster area to the weapon frame though a subcaliber barrel inserted through the main gun barrel and anchored to the muzzle of the main gun barrel.




In the second embodiment, in addition to the reaction of the propellant gas against the primary booster area, as in the first embodiment, a secondary chamber with a secondary booster area is provided to trap gas to apply force for a longer period of time. Propellant gas is released from the subcaliber cartridge chamber into the secondary booster chamber when pressure in the subcaliber chamber exceeds the strength of the subcaliber cartridge case wall at the chamber vent, perforating the subcaliber cartridge case wall at the subcaliber chamber vent. In this embodiment, gas escaping into the secondary chamber of the adaptor pressurizes a larger area (e.g. ten to twenty times greater) than the projected bore area of the subcaliber cartridge projectile. Gas is trapped in the secondary booster by the restriction of the gas vent which admitted the highly pressurized gas from the subcaliber chamber, much as gas is trapped in the gas cylinder of a conventional gas operated gun mechanism.




The third embodiment is like the second embodiment except the secondary chamber is vented to the atmosphere to limit the operating force to that of the primary booster area by eliminating force (rather than adding force) from the secondary booster. This embodiment is required when a standard cartridge such as the 7.62 mm NATO is used, but which provides excess power with the Mk 19. It is desirable to use standard 7.62 mm machinegun ammunition due to its low cost and ready availability.




A fourth embodiment permits the subcaliber device to be converted into a blank firing adaptor related to U.S. Pat. No. 5,438,907 by the installation of a vented restrictor disc at the front of the muzzle of the subcaliber barrel. The vented restrictor disc sufficiently contains the blank generated pressurized gas to operate the weapon. Blank cartridges operate at such low pressure when operated with a large free volume, that the cartridge case wall will not perforate at the booster vent to release gas into the secondary booster chamber. The vented restrictor disc is retained by a vented muzzle cap which also serves as a bullet trap in case a bulleted cartridge is accidently fired when normally using blanks. If a rifle grenade launching cartridge, which is much more powerful than a blank, is accidently fired, the higher pressure of the grenade cartridge bursts the vented restrictor disc, preventing the high power of the grenade cartridge from damaging the gun mechanism. The vented restrictor disc is inexpensive and easily replaced.




In the first three embodiments the operating force of the subcaliber cartridge is multiplied above that available through straight blow-back by a factor equal to the ratio of the projected area of the bore of the subcaliber cartridge to the area of the total booster areas affected by the gas. This fully powers the weapon while using a cartridge less than {fraction (1/20)} the weight and {fraction (1/50)} the cost of the least expensive training cartridge the weapon was designed for. By adjusting the booster area(s), initial volume, length of power stroke, diameter of perforation, projectile weight and by selecting powder burning rate the subcaliber device and cartridge can be designed to launch a subcaliber projectile at the same velocity (or higher or lower) as the service projectile. Thus the trajectory of the service round can be closely duplicated provide realistic training. Tracer ammunition can be used where range conditions permit, or ball ammunition can be used where dry range conditions prohibit the use of tracers.




The total blowback force is equivalent to that generated by a full caliber service round, but the reaction is primarily against the gun itself through the subcaliber barrel and muzzle cap attached to the muzzle of the weapon barrel instead of reacting only against the projectile as in straight blow-back operation. In the case of the 40 mm Mk19 subcaliber device using a 1.300 inch diameter secondary booster area and firing a 0.308 diameter subcaliber bullet, the effective total blowback area is approximately 19 times the area of the subcaliber projectile. Thus it is possible to obtain from approximately twenty grains of powder (when firing a 214 grain subcaliber projectile at approximately 790 feet per second muzzle velocity) more than enough power to operate the Mk19 with its approximately 17 pound bolt.




The Mk19 is normally provided with a bag for catching empty cartridge cases. After firing with the subcaliber device/blank firing adaptor, the soldier in the field collects the empty cartridge case adaptors from the catch bag and ejects the expended subcaliber cartridge cases from the cartridge case adaptors. Fresh subcaliber cartridges or blanks are inserted into the cartridge case adaptors. and the cartridge links are repositioned on the cartridge case adaptors. The cartridge case adaptors are re-linked into a belt. This process is accomplished using a simple hand operated fixture which is not part of this invention.




The basic principle of operation of the subcaliber device is typical of other subcaliber devices, except a close ballistic match is achieved between the subcaliber projectile and the service projectile while powering the weapon. In straight blow-back operated weapons,




MV of the bolt=MV of the projectile (neglecting shot start, projectile engraving and friction)




where M=mass and V=velocity.




In the Mk 19 the projectile weighs approximately 0.6 lbs, and has a muzzle velocity of 790 feet per second. The Mk 19 bolt weighs approximately 17.25 lbs. Applying MV=MV;




(0.6 lb)(790 fps)=(17.25 lbs)(X fps), or X=approximately 27.5 feet per second bolt velocity.




But in a subcaliber device, if the booster diameter is 1.30 inch and the subcaliber projectile diameter is 0.308 inch, then the ratio of the areas of the booster and the subcaliber projectile is about 17.8/1. This means the subcaliber projectile at 0.308 caliber, if it has the same sectional density as the service projectile, needs only weigh 1/17.8th of the service projectile to provide the same effective reaction is the service projectile, because:




F=PA where F=force, P=pressure, and A=area




With the same pressure acting on the projectile with its small area and the booster with its large area. the force applied to the larger area of the booster is in direct proportion to the ratio of the large area to the small area.




Another way of stating this is that any diameter of subcaliber projectile may be used, as long as its effective sectional density is the same as that of the service projectile (if the subcaliber projectile is to have the same muzzle velocity as the service projectile). This is neglecting shot start, engraving, and friction forces which are considerable, but which are relatively easy to compensate for.




The invention can also be applied to recoiling barrel weapons by anchoring the subcaliber barrel to the weapon frame rather than to the weapon barrel.











BRIEF DESCRIPTION OF DRAWINGS





FIG. 1

is a plan view in section of a cartridge case adaptor and a subcaliber cartridge.





FIG. 2

is a plan view in section of the essential components of the weapon.





FIG. 3

is a plan view in section of the subcaliber cartridge case adaptor with a subcaliber cartridge loaded into the weapon.





FIG. 4

is a plan view in section of a first embodiment during firing.





FIG. 5

is a plan view in section of a second embodiment during firing.





FIG. 6

is a plan view in section of a third embodiment during firing.





FIG. 7

is a partial plan view in section of a fourth embodiment showing how any of the other embodiments are converted into a blank firing adaptor.





FIG. 8

is like

FIG. 7

, but where a bulleted cartridge has accidentally fired.











DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS




Referring to

FIG. 1

, the outer configuration of a cartridge case adaptor


18


fits the weapon feed system (not shown) and chamber. The cartridge case adaptor


18


is provided with a subcaliber cartridge chamber


34


with an enlarged chamber neck


68


. The enlarged chamber neck


68


is significantly larger in diameter than the cartridge case neck of the subcaliber cartridge case


10


of the subcaliber cartridge


36


. The subcaliber cartridge chamber


34


of cartridge case adaptor


18


is axially located in the cartridge case adaptor


18


to receive a subcaliber cartridge


36


consisting of a subcaliber projectile


32


, a subcaliber cartridge case


10


, with propellant


42


and a primer


16


. The cartridge case adaptor


18


is reusable.




Referring to

FIG. 2

the flash suppressor of the weapon barrel


22


has been replaced with a muzzle cap


28


. Attached to muzzle cap


28


is a subcaliber barrel


24


with its centering ring


26


. The subcaliber barrel


24


is attached to the muzzle cap


28


, so that when assembled, the weapon barrel


22


, muzzle cap


28


and subcaliber barrel


24


do not move relative to each other. The centering ring


26


centers the subcaliber barrel


24


on the axis of the weapon barrel


22


.




Referring to

FIG. 3

a cartridge case adaptor


18


with a subcaliber cartridge


36


has been placed in the weapon barrel


22


. Weapon bolt


20


is in contact with the base of cartridge case adaptor


18


and with the base of the subcaliber cartridge


36


. The front of projectile


32


has entered the rear of the bore of subcaliber barrel


24


. Since the weapon is not locked, but is blowback operated, the mass of the weapon bolt


20


supports the cartridge case adaptor


18


with its subcaliber cartridge


36


in the weapon barrel


22


.




Referring to

FIG. 4

the first embodiment of the subcaliber device of

FIGS. 2 and 3

is in the act of firing. The burning propellant has generated pressurized gas


52


applying sufficient force to expand the unsupported neck of the cartridge case


10


against the enlarged chamber neck


68


, releasing pressurized gas


52


past the base of subcaliber projectile


32


into the volume between a second primary booster area


44


and a first primary booster area


54


of subcaliber barrel


24


. Pressurized gas


52


also acts against the base


38


of subcaliber projectile


32


to provide shot start, projectile engraving and to drive the projectile through the bore of subcaliber barrel


24


. The pressurized gas


52


, acting equally in all directions also applies pressure against the projected area


46


equal to the area of the diameter of the inside of the neck of subcaliber cartridge case


10


at the enlarged chamber neck


68


. The total force of the pressurized gas


52


acting through the cartridge case adaptor


18


against the weapon bolt


20


is the sum of the force applied to the projected area


46


plus the force applied to the projected area


44


of the primary booster.




Referring to

FIG. 5

as the second subcaliber device embodiment which provides power to the weapon bolt


20


for a longer period of time than the first embodiment for a given subcaliber cartridge. The burning propellant has generated pressurized gas


52


applying sufficient force against the base


38


of subcaliber projectile


32


to provide shot start, projectile engraving and to drive the projectile through the bore of subcaliber barrel


24


. The pressurized gas


52


, acting equally in all directions also applies pressure against the projected area


46


equal to the area of the base


38


of the subcaliber projectile


32


. The pressurized gas


52


also acts against the first primary booster area


54


of the subcaliber barrel


24


, and against the projected second primary booster area


44


of the cartridge case adaptor


18


. A subcaliber chamber vent


12


is provided, connecting a subcaliber cartridge chamber


34


with a secondary booster chamber


14


. The wall of the subcaliber cartridge case


10


, at the subcaliber chamber vent


12


, is not strong enough to contain the full pressure of the pressurized gas


52


. The pressurized gas


52


causes the wall of the cartridge case


10


to fail at the subcaliber chamber vent


12


, releasing pressurized gas into a secondary booster chamber


14


and pressurizing booster chamber


14


to apply pressure against projected area of secondary booster chamber


40


. With the fast burning powder used, (such as Hercules Unique, Hercules Bullseye or Winchester-Western 296 ball powder) rupture of the subcaliber cartridge case wall takes place virtually at the moment of shot start of subcaliber projectile


32


.




Making the subcaliber chamber vent


12


small results in temporarily trapping high pressure gas within the secondary booster chamber


14


after the projectile


32


has exited the muzzle of the subcaliber barrel


24


. This corresponds to gas expansion type gas operated gun mechanisms. In other applications, making the subcaliber chamber vent


12


large causes the subcaliber cartridge case


10


to vent quickly into the secondary booster chamber


14


after firing, and to vent quickly back into the subcaliber cartridge chamber


34


upon muzzle exit of subcaliber projectile


32


, corresponding to gas impingement type gas operated gun mechanisms. The total force of pressurized gas


52


acting through cartridge case adaptor


18


against weapon bolt


20


is the sum of the force applied to the projected area of the subcaliber bore


46


plus the force applied to the projected area


44


of the primary booster plus the force applied to the projected area


40


of the secondary booster chamber


14


.




A rebound spring


50


can be provided to assist in arresting the weapon bolt


20


as weapon bolt


20


goes into battery, compressing the rebound spring


50


and storing some of the energy of the counter-recoiling weapon bolt


20


. The potential energy stored in rebound spring


50


is later given back to boost recoil of weapon bolt


20


at the time of firing.




Referring to

FIG. 6

as the third subcaliber device embodiment which provides for venting excess gas if a standard rifle or machine gun cartridge is used in the design. The burning propellant has generated pressurized gas


52


applying sufficient force against the base


38


of subcaliber projectile


32


to provide shot start, projectile engraving and to drive subcaliber projectile


32


through the bore of subcaliber barrel


24


. The pressurized gas


52


, acting equally in all directions also applies pressure against the projected area


46


of subcaliber projectile base


38


. The pressurized gas


52


also acts against primary booster area


54


of subcaliber barrel


24


, and against the projected primary booster area


44


of the cartridge case adaptor


18


. A subcaliber chamber vent


12


is provided which connects the subcaliber cartridge chamber with the secondary chamber


14


which is vents through a booster vent


48


and thence through muzzle cap vent


30


in muzzle cap


28


.




The total force of the pressurized gas


52


acting through the base of subcaliber cartridge case


10


and cartridge case adaptor


18


against weapon bolt


20


is the sum of the force applied to the projected area of the subcaliber bore


46


plus the force applied to the projected area


44


of the primary booster. There is negligible force applied to the projected area


40


of the secondary booster chamber


14


because the pressurized gas


52


is released from secondary booster chamber


14


through secondary booster vent


48


, centering ring vent


58


and muzzle cap vent


30


.




Referring to

FIG. 7

which shows the subcaliber device adapted to serve as a blank firing adaptor. A vented restrictor disc


60


has been placed into the front of muzzle cap


28


. The restrictor disc


60


is retained by a vented muzzle plug


66


which is secured to muzzle cap


28


. Vented restrictor disc


60


is provided with a vent hole


62


. Upon firing of a blank cartridge in the chamber, not shown, pressurized gas will fill the bore of subcaliber barrel


24


. The pressurized gas will apply sufficient force to the cartridge case adaptor, not shown, to power the weapon. The vent hole


62


of vented restrictor disc


60


is sized to retain enough pressurized gas to operate the weapon and to release the remaining gas to make noise to simulate muzzle blast.




The vented muzzle plug


66


is provided with a bullet trap


64


sufficient to arrest the projectile if a bulleted cartridge is accidentally fired.




Referring to

FIG. 8

which is like

FIG. 7

, but where a bulleted cartridge has accidentally been fired. The projectile


32


has perforated vented rupture disc


60


. Projectile


32


has been arrested in bullet trap


64


of vented muzzle plug


66


. The pressurized gas


52


is passing through the large hole created in the vented restrictor disc


60


by projectile


32


. The pressurized gas


52


is vented to the atmosphere through muzzle plug vents


70


in vented muzzle plug


66


.




NOMENCLATURE LIST






10


Subcaliber cartridge case






12


Subcaliber chamber vent






14


Secondary booster chamber






16


primer






18


cartridge case adaptor






20


weapon bolt






22


weapon barrel






24


subcaliber barrel






26


centering ring






28


muzzle cap






30


muzzle cap vent






32


subcaliber projectile






34


subcaliber cartridge chamber






36


subcaliber cartridge






38


base of subcaliber projectile






40


projected area of secondary booster chamber






42


propellant






44


primary booster






46


projected area of subcaliber bore






48


secondary booster vent






50


rebound spring






52


pressurized gas






54


primary booster area of subcaliber barrel






56


secondary booster area of subcaliber barrel






58


centering ring vent






60


vented restrictor disc






62


hole in vented restrictor disc






64


bullet trap






66


vented muzzle plug






68


enlarged subcaliber chamber neck






70


muzzle plug vent



Claims
  • 1. A subcaliber cartridge and a firearm apparatus for firing a projectile of the subcaliber cartridge, comprising:a subcaliber barrel disposed within a barrel of the firearm, said subcaliber barrel including a first primary booster area at one end and a bore extending to an opposite muzzle end; and a cartridge case adaptor including a second primary booster area, said cartridge case adaptor positionable with respect to said subcaliber barrel by a bolt of the firearm to form a volume between said first primary booster area and said second primary booster area, said cartridge case adaptor including a subcaliber cartridge chamber coaxial with said subcaliber barrel bore, said chamber having an enlarged neck portion, wherein said volume communicates with said enlarged neck portion when said subcaliber cartridge is disposed within said chamber thereby allowing passage of pressurized gas from said chamber to said volume when said subcaliber cartridge is fired and the projectile of said subcaliber cartridge is positioned within said enlarged neck portion.
  • 2. The apparatus of claim 1, further including a centering ring disposed between the firearm barrel and said subcaliber barrel.
  • 3. The apparatus of claim 1, wherein said cartridge case adaptor is reusable.
  • 4. The apparatus of claim 1, wherein the projectile of said subcaliber cartridge extends from said enlarged neck into said bore of said subcaliber barrel when said subcaliber cartridge is positioned in said chamber.
  • 5. A method for increasing the blowback force created upon firing a projectile of a subcaliber cartridge from a firearm, comprising:(a) providing a subcaliber barrel disposed within a barrel of the firearm, said subcaliber barrel including a first primary booster area at one end and a bore extending to an opposite muzzle end; (b) providing a cartridge case adaptor including a second primary booster area and a subcaliber cartridge chamber coaxial with said subcaliber barrel bore, said subcaliber cartridge chamber including an enlarged neck portion; (c) inserting the subcaliber cartridge in the subcaliber cartridge chamber; (d) positioning said cartridge case adaptor with respect to said subcaliber barrel with a bolt of the firearm to form a volume between said second primary booster area and said first primary booster area; and (e) firing the firearm so pressurized gas passes through the enlarged neck around the projectile to said volume.
  • 6. A subcaliber cartridge and a firearm apparatus for firing the subcaliber cartridge, comprising:a subcaliber barrel positioned within a barrel of the firearm, said subcaliber barrel including a first primary booster area at one end and a bore extending to an opposite muzzle end; and a cartridge case adaptor including a second primary booster area, said cartridge case adaptor positionable with respect to said subcaliber barrel by a bolt of the firearm to form a volume between said first primary booster area and said second primary booster area, said cartridge case adaptor including a subcaliber cartridge chamber coaxial with said subcaliber barrel bore, wherein said volume communicates with said chamber thereby allowing passage of pressurized gas from said chamber to said volume when the subcaliber cartridge is fired.
  • 7. The apparatus of claim 6, further including a centering ring disposed between the firearm barrel and said subcaliber barrel.
  • 8. The apparatus of claim 6, wherein said cartridge case adaptor is reusable.
  • 9. The apparatus of claim 6, wherein said subcaliber cartridge chamber includes an enlarged neck portion.
  • 10. The apparatus of claim 9, wherein said volume communicates with said enlarged neck when said subcaliber cartridge is disposed within said chamber thereby allowing passage of pressurized gas from said chamber to said volume when the subcaliber cartridge is fired and a projectile of said cartridge is positioned within said enlarged neck portion.
  • 11. The apparatus of claim 9, wherein a projectile of said subcaliber cartridge extends from said enlarged neck into said bore of said subcaliber barrel when said subcaliber cartridge is positioned in said chamber.
CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of co-pending U.S. patent application Ser. No. 08/924,054, filed Aug. 28, 1997, now issued as U.S. Pat. No. 5,983,772.

US Referenced Citations (10)
Number Name Date Kind
353231 Morris Nov 1886
533171 Hurst Jan 1895
1217162 Egbers Feb 1917
2898693 Ruger Aug 1959
3363509 Tschoepe Jan 1968
3411229 Gronemann Nov 1968
3744370 Snodgrass Jul 1973
5377438 Sheinfield et al. Jan 1995
5438907 Reynolds et al. Aug 1995
5492063 Dittrich Feb 1996
Foreign Referenced Citations (7)
Number Date Country
730030 Jan 1943 DE
1195205 Jun 1965 DE
340829 Nov 1989 EP
662545 Aug 1929 FR
1496220 Sep 1967 FR
8102 Jan 1894 GB
874 Jan 1907 GB
Continuations (1)
Number Date Country
Parent 08/924054 Aug 1997 US
Child 09/360272 US