Patent Grant
11262171
The present invention relates to cartridges for firearms, in particular to casings for ammunition.
In the field of firearms, ammunition cartridges (also called ammunition shells and “rounds”) contain powder, which when ignited propels a bullet down the barrel of a gun toward a target. Prior art cartridges, particularly those for use with small arms, typically comprise a casing made of forged brass. A propellant, typically smokeless explosive powder, is contained within the casing and is ignited by impact of a firing pin of the breech block of the gun on a primer that is set in a recess at the base of the casing.
A cartridge relevant to the present invention comprises a generally cylindrical casing having a substantially closed end, called here the base end, and an opposing open end, often called the mouth. The open end of the mouth receives a bullet after propellant is put into the concavity of the casing; and the casing is crimped as needed around the bullet to hold it in place. The base end of the casing typically has a cannelure or groove to enable the casing to be engaged by grips on the firing mechanism of a gun. The base end often comprises a larger diameter flange portion which acts as a stop, limiting the depth of insertion of the cartridge into the chamber of the barrel of the gun.
In prior art cartridges comprised of forged metal (typically cartridge brass) casings, the base end which holds the primer is integral with the sleeve portion which holds the bullet. Typically, the sleeve is tapered internally (with the larger diameter at the open end), attributable to the metalworking process by which the cartridge is formed. The wall thickness near the base may is as several times the thickness of the wall at the mouth end. Sometimes a casing has a step-down in diameter in vicinity of the open end, where the bullet is captured.
The exterior surface of the base of the typical cartridge has a recess within which is contained a percussion primer that contains a small quantity of impact-sensitive explosive powder. Typically, the primer is in the center of the base and comprises an internal anvil which is supported during the firing process by the end of the recess. There is a small passageway through the base, often called the vent or flash hole, enabling ignited primer gases to pass through the base and into the concavity of the casing, to ignite the propellant.
A cartridge necessarily slip-fits into a chamber of the barrel of the gun for which it is intended. A cartridge is typically inserted and held in place by the breech block (also called slide or bolt) which usually has one or more claws for grasping the groove in the rim of the base of the casing. When the primer is struck by the firing pin within the breech block of the gun, the propellant explosively turns into gas and forces the bullet from the cartridge and down the bore of the barrel of the gun. In that process, the pressure of the deflagrated propellant gas expands the casing of the cartridge radially outwardly, desirably creating a seal against gas escape through the slip fit clearance region of the casing with the chamber. Then the casing hopefully relaxes, moving radially inwardly to about its original dimension, enabling the casing of the spent cartridge to be readily removed. A casing is often removed from the chamber by retracting action of the breech block which pulls on the cannelure; or by force of the pressurized gases on the casing in coordination with rearward motion of the breech block. After ejection from the breech area, a casing may often be recycled by replacing the primer and powder and installing a new bullet.
There are differences in peak deflagration pressures that occur during firing of a cartridge, according the size of the cartridge and the volume of gunpowder it holds. Peak pressures, e.g., 20,000-30,000 pounds per square inch (psi), are typically encountered in cartridges firing bullets in handguns. A 9 mm pistol cartridge is an example. Comparatively high pressures, for e.g., 40,000-60,000 psi can be encountered in cartridges firing bullets in rifles, particularly military rifles. A 7.62 mm rifle cartridge is an example.
Good cartridges have a number of desired characteristics, with the ranking determined by a particular customer and application. Generally stated, cartridges and casings desirably have the following features. They should be strong enough to resist fracture or distortion which causes jamming, when subjected to the pressure of deflagration gases as just discussed. They should be configured for making a seal with the chamber of the gun during firing of a bullet; and they should be readily extractable from the chamber. They should have general durability and integrity, including the ability to resist possible rough handling prior to placement in a firearm and the ability to be reworked and reloaded. They should be corrosion resistant. Traditionally, cartridges of brass alloys had worked well. Further, particularly for military applications there is a desire for a casing that is as light as possible particularly when quantities of cartridges are carried by an aircraft or by a soldier.
The brass of common and widely used traditional casings is a costly alloy compared to various iron and aluminum alloys, and of course, compared to plastic. However, alternative materials such as steels, aluminum alloys and plastics have found less favor in the marketplace, usually due to perceived deficiencies in the characteristics above.
Other inventors have described a variety of alternative constructions and materials for cartridges. For example: Cartridges may be made in whole or part from plastics and metals other than brass. The casing may be made of plastic or paper and attached to a metal base (as is common for shotgun shells). The casing may be made in the form of a sleeve having a nipple end which is inserted into a passageway in a base that runs to a primer, and the nipple is flared radially, to hold the two parts together. For reference see the following publications: Milbank U.S. Pat. No. 125,830; Horn U.S. Pat. No. 3,688,699; Skochko U.S. Pat. No. 3,765,297; Anderson U.S. Pat. No. 3,977,326; Horn U.S. Pat. No. 3,688,699; Dittrich U.S. Patent Publications 2007/0214992 and 2008091245, and Neugebauer U.S. Patent Publication 2014/0224144. Based on the absence from the marketplace for most if not all of the foregoing kinds of casings and cartridges, it would appear further improvements are needed.
Further desirable characteristics of casings include the following: For economic and environmental reasons, spent casings that are expelled from a gun after firing will be amenable to being readily gathered up; when casings are made of brass or plastic that basically means using visual or optical means. Also, for economic and environmental reasons, a casing will be able to be re-used; but the construction of many prior art casings does not lend itself to one or more re-uses. There is always a desire for a lower cost cartridge, particularly for small arms cartridges that are used in large quantities. And there is always a continuing desire to improve the performance of cartridges. For example, for any particular caliber of cartridge it is generally desirable to maximize the volume within which gunpowder is contained.
An object of the invention is to provide a cartridge use in a firearm, which is improved with respect to being light in weight and economic to manufacture, corrosion resistant, resistant to damage in handling, accommodative of primers currently in use, and suited for re-loading after use. A further object is to have a cartridge comprised of a casing which is attracted by a magnet to enable improvement in such gathering of spent casings. An object of the present invention is to make a lower cost cartridge, particularly for small arms, which is equal or better than prior art cartridges.
In embodiments of the invention, a cartridge for a firearm comprises a casing. In one embodiment, a casing comprises a sleeve which is secured to a base by means of a hollow nipple that extends from a bulkhead at one end of the sleeve and that is fastened in a passageway through the base. The opposing lengthwise end of the sleeve is cylindrical and comprises a mouth for holding a bullet or other closure. A recess in the passageway receives a primer. The bulkhead of the sleeve contacts or is intimately disposed at the first surface of the base. The terminal end of the nipple flares as a lip that sealingly engages a shoulder of the recess. In a casing embodiment there are two seals within the passageway, along the length of the nipple, one near the bulkhead and one at the lip/shoulder; and the seals are spaced apart by a tapered cylindrical void space around the nipple.
In another embodiment of the invention, the terminal end of the nipple which comprises a lip has, in casing lengthwise cross section, a special shape: (a) a first side of the lip is in contact with the shoulder, which is preferably runs at 90 degrees to the casing length; and (b) a second side (that faces the primer) is contoured and thinner at the lip outer rim than nearer the passageway (flash hole) through the nipple. The second side of the lip is contacted by the legs of the anvil of the primer in an advantageous way and enables an increased diameter of flash hole.
In other embodiments of the invention, the bulkhead has one or more depressions on the side which mates with the end of the base, preferably there is one or more circular waves or ridges centered on the lengthwise axis and the nipple. The wave creates a depression or hollow, and thus a space between the bulkhead and the surface of the base when the bulkhead is in contact therewith; and the wave creates a raised region in the gunpowder-holding concavity of the sleeve. The bulkhead is un-restrained by the surface of the base; i.e. there is no interlock or fastener other than by means of the nipple. Thus, the wave enables the bulkhead to expand radially during the pressure transient associated with firing a bullet, so the outer surface of the sleeve can contact the bore of the chamber and so that there are lesser stresses than would otherwise be present, to cause premature failure.
Another casing embodiment has a base with a surface having the same diameter as the bulkhead that abuts it, and the cannelure is spaced apart from said base surface, also to lessen stresses and enable a thin wall in the sleeve. In other embodiments, for resisting the high pressures associated with certain rifle rounds, such as a 7.62 mm NATO round, the distal end of the base and the mating bulkhead of the sleeve both have conical portions, preferably with annular portions that are either, or both, adjacent the passageway/nipple and adjacent the cylindrical outer edge of the base. Optionally, there is a thin skirt around the edge of the base to provide support to the edge of the sleeve where the cylindrical sleeve surface meets the bulkhead.
In other embodiments, the cannelure of a base, particularly one made of steel and one preferably having the aforementioned conical feature, is substantially larger (deeper) than, and differently shaped from, a prior art cannelure. There is an annular surface at the cannelure end where an extraction arm grabs the casing; and there is a continuously curved surface extending in the lengthwise direction, to a location close to where the sleeve bulkhead is mated with the base. A cannelure embodiment has an innermost or groove-depth diameter DTT which is between about 60 and about 80 percent of the outside diameter DWW of the base, and a volume which is between about 20 and about 43 percent of the volume of a like-base which has no cannelure.
In another embodiment, the casing is made of an austenitic stainless steel having the special character of becoming magnetic when cold-worked. The sleeve has a cylindrical mouth wall portion of a first hardness and a first permeability, a bulkhead with a lesser hardness and permeability, and a nipple with a still lesser hardness and permeability. Thus, the lip which holds the sleeve fixed to the base can be more easily formed. The cylindrical part of the casing will be drawn to a magnet, sufficient thereby to facilitate retrieval of spent casings. And the base is preferably made of an aluminum alloy which has a hardness that is less than any part of the sleeve.
Different combinations of the foregoing embodiments are useful. The present invention also comprises the method of making a casing and a cartridge which have the desired features described above.
A cartridge having a casing of the present invention fulfills the objects of the invention. The casing is stronger than the prior art brass cartridge casings for which it is substitutional. A casing has increased volume that enables use of slower burning powder. A casing is exceptionally durable and resists fatigue failure. It can be reloaded and fired many more times than a conventional cartridge. The foregoing and other features and advantages will be fully appreciated from the more detail description which follows and associated drawings.
Some aspects of the present invention relate to the mechanical configurations of the casing and its components, where the materials do not necessarily have a desirable unique combination of properties. The mechanical configurations of invention embodiments include how the sleeve and base are each shaped and how they mate with each other. In brief: A sleeve has a nearly constant thickness cylindrical wall portion, a bulkhead portion which optionally has a wave (annular ridge), and the terminal end of the nipple flares outwardly within the base to form a lip, thereby holding the sleeve to the base. The lip has a surface shape that is suited to support the primer. The invention casing has superior interior volume compared to prior art casings of the same exterior size.
While cartridges and casings having the foregoing features can be made using various materials, embodiments of the present invention involve materials with special properties and combinations of properties. In brief: Embodiments of the present invention comprise a sleeve which is made of an austenitic stainless steel that is hardened and magnetic, and the base is made of a softer metal, such as aluminum base alloy.
The mechanical aspects of the invention are concentrated on first in the following description. A casing of the present invention may be made of different materials and combinations of materials. Preferably, as discussed in greater detail below, a sleeve is made of austenitic stainless steel having a martensitic microstructure and the base is a wrought aluminum alloy.
With reference to the partial cross section of base 124 in
During manufacturing of a casing, sleeve nipple 128 is placed into passageway 130 of the base and is flared radially outwardly to engage shoulder 144, as indicated by the phantom and arrow D in
In the invention, when the sleeve is viewed in lengthwise cross section, a preferred lip has a curved surface portion on the lip surface that faces in the direction of the end of the base which has the recess for a primer. The opposing side of the lip sealingly sets on a shoulder in the passageway of the base. Restated, a preferred sleeve has a lip that is thinner at the lip rim or outer edge than at the place where the nipple commences to run down the passageway of the base, in combination with a surface which is wholly or partially curved. An advantage of the thinner outer edge and the curved second surface will be appreciated below in the description related to
A preferred sleeve comprises a nipple which is particularly amenable to being flared with the desired shape and sealing effect. The chamfering of the nipple tip or terminal end and the stretching during flaring achieve the desired configuration. As described below, an effective seal is also a result of choice of preferred material and fabricating process, which result in differential properties along the length of the nipple within a base. In particular, preferably the tip of the nipple is softer than the rest of the sleeve, which has a desired combination of high hardness, high strength, and magnetic character.
As described below in connection with
While the shoulder onto which the lip is flared is preferably at 90 degrees to the length axis of the base and casing, in alternative embodiments the shoulder be frusto-conical shaped. In such instance, a thin-rim lip may present as a surface that is 90 degrees to the length axis. In a further alternate embodiment of the invention, the lip has a substantially constant thickness. To carry out this embodiment, when first formed, the nipple may have little or no chamfer at its terminal end, and during the flaring or lip-forming process the material at the end of the nipple is gathered and otherwise worked appropriately by one or more forming tools.
In an embodiment of the invention, a nipple may slip into the passageway 156 and there is only a first seal associated with lip 134. Preferably, there is a second seal between the nipple and the base within the bore of passageway 156, more preferably in proximity to the bulkhead.
In one way of constructing a casing having the two spaced apart seals, passageway 156 is of constant diameter and the exterior of the nipple is tapered. With reference to sleeve 222 in
In another embodiment of casing, passageway 156 tapers at angle BB as shown in
As mentioned above, in another embodiment of casing where there is no second seal, the relative shapes of the nipple exterior and the bore of passageway 156 may be such that there is no press fit along the length of the nipple, and only the lip at the terminal end. In any of the embodiments, optional use may be made of an organic or inorganic sealant around the nipple or at the lip location.
The bore of a nipple may be straight or tapered; preferably the nipple has a wall thickness that is approximately the same as the thickness of the cylindrical section of the sleeve. As shown in
Referring again to
In
To carry out the purpose just mentioned, and for appearance reasons, there ought to be a minimum gap between the edge or corner 140, 240 and the bulkhead, surface 136. One way of helping to achieve that circumstance is to have an angle A as shown in
When a casing of the present invention is fitted with propellant and a bullet and inserted into the chamber of a firearm, it should slip fit into the chamber. For example, the clearance may be a few thousandths of an inch on each side of a typical cartridge having an about 0.386 inch (9.8 mm) outside diameter. During firing of the bullet there is great internal pressure rise which forces the cylindrical wall radially outward against the chamber of the gun. In embodiments of the invention, the casing will elastically deform radially outwardly during the deflagration of the propellant, then elastically to return to near its original dimensions, sufficient to enable easy removal of the spent casing from the chamber of the firearm. However, when there is outward expansion, excess stresses can be created at the circumferential location 140 where the sleeve bulkhead meets the cylindrical wall. It has been discovered through analysis and experiment that a propensity for failure at location 140 is mitigated by either or both (a) making the radius of curvature at location 140 sufficiently small; and (b) providing a circular wave 250, or ridge, on the bulkhead.
With respect to the radius: For a sleeve embodiment having a wall thickness of about 0.012 inch (about 0.3 mm), the mean radius of curvature at location 140 is preferably less than about 0.12 inches (32 mm); more preferably less than about 0.05 inches (1.27 mm). Larger radii make a casing more prone to failure. Still more preferably the radius is about 0.008 inches (0.2 mm) as measured at the inside surface, about 0.020 inches (2 mm) as measured at the outside surface, with a mean radius of about 0.014 inches (0.36 mm). In another preferred embodiment the mean radius is less than about two times the thickness of the material.
A preferred bulkhead has a wave that (a) creates a depression on the exterior side of the bulkhead (that facing the base) and (b) is not restrained by engagement with the abutting surface of the base. The wave defines an annular depression or hollow 258 on the exterior surface of the bulkhead. The bulkhead is preferably of constant thickness and is in contact with or in very close or intimate proximity to the surface 236 at the end of the base; and the wave defines a void space between the bulkhead and the surface 236. When propellant is deflagrated within the casing, the presence of a wave lowers the von Mises stresses at region 240, where the cylindrical sidewall of the sleeve meets the bulkhead. It is believed that the high gas pressure within the casing when gunpowder is ignited causes the wave to elastically deform, or to flatten. That allows both the outside circumferences of the bulkhead and the adjacent sleeve cylindrical portion at location 240 to increase—to the point that they contact the bore of the chamber within which the cartridge is positioned, thereby to make momentarily a seal that inhibits flow of gun barrel gases between the casing and the chamber bore. In the invention, there is no ridge or engagement feature on the base surface, and the bulkhead is able to move radially relative to the surface 236. Preferably the aforementioned small radius of curvature is present at region 240 in combination with a wave.
The void space which the wave creates between the bulkhead and the abutting surface 236 of the end of the base is in addition to whatever small void space may be present in the region because of any difference in angling between the bulkhead and the abutting surface of the base.
In an example of the invention where the sleeve has a wave, the diameter of a 0.010-0.012 inch (0.25-0.30 mm) thick cylindrical wall of a sleeve is about 0.39 inches (9.9 mm) in diameter, a wave 250 will have a mean diameter of about 0.23 inches (5.8 mm) and will project a dimension h of about 0.002 to 0.050 inches (0.05 to 1.27 mm), more preferably about 0.002-0.010 inches (0.051-0.25 mm) from the mean interior surface of the bulkhead. The projection h may be referred to as the height of the wave.
To summarize, in the generality of this aspect of the invention, a casing has a bulkhead with one or more depressions on the surface facing the base. A first bulkhead surface of said wave projects or protrudes into the concavity of the sleeve, and the second opposing side surface of the bulkhead has an associated depression or hollow. Other bulkhead configurations may achieve the object of this aspect of the invention.
The outer edge or rim 35 of lip 34 is thinner than the rest of the lip, as discussed in connection with
For a given external shape cartridge, the present invention can provide a larger diameter flash hole larger volume casing, compared to a same exterior shape prior art one piece cartridge.
The invention enables an increased diameter VI of the flash hole 29 in casing 20, compared to diameter VP of flash hole 29A in prior art casing 21, aided by the shape of lip 34 which in providing good support for the feet of the anvil of a primer, enables a smaller width of land at the bottom of the recess 32.
Casing 20 has a flash hole 29 which has increased diameter VI, compared to diameter VP of flash hole 29A in prior art casing 21. The increased diameter is achieved with the aid of the shape of lip 34, which in providing good support for the feet of the anvil of a primer, enables a smaller width of land at the bottom of the recess 32. The flash hole of sleeve 22 is larger in diameter than the diameter DA of the innermost bounds of the anvil feet. Diameter DA is the diameter of a circle CA which touches the innermost portions of the feet 60 of an anvil 51 of a primer. See
Since steels having a higher strength than cartridge brass may be used in a casing of the present invention, thinner casing walls are useful. An exemplary casing of the invention has a nearly uniform wall thickness t of about 0.010 to 0.012 inches (0.25 to 0.3 mm). That is about 0.0.15 inches (0.381 mm) less than the average 0.027 inch (0.59 mm) wall thickness of an exemplary prior art casing 21. Thus the average internal diameter D1 of casing 20 is larger than the average diameter DP of casing 21; and, there may be an about 4 to 15 percent more volume within the casing, for the powder characteristic of an assembled cartridge. Typically a cartridge maker uses a gunpowder which fills the concavity 31, 31P of the casing, when the bullet is in place. In general, to achieve certain desirable pressure vs. time change within the barrel of a gun that enhances bullet velocity and repeatability, it is desirable to have larger volume of reduced burn rate powder, compared to having a smaller volume of high burn rate powder. The present invention enables that desirable result. Tests have shown a higher repeatability in bullet velocity at the exit of the barrel of a gun, and that results in more accurate targeting of the bullet.
In the generality of the invention which involves the foregoing mechanical features, a sleeve may be made of iron alloys (e.g., steels) and preferably other alloys having iron, aluminum, and copper base. As noted just above, the best performance of an invention casing/cartridge is achieved when the material of the sleeve has high strength.
Preferably, an exemplary sleeve of a casing of the present invention is made of a kind of austenitic stainless steel which is cold worked sufficient to form a martensitic microstructure, to thereby selectively both harden and make magnetic the steel, compared to the same steel in its annealed condition. A preferred material for the base is 7075 wrought aluminum alloy in T6 temper.
A preferred austenitic stainless steel is AISI 304 stainless steel alloy. Other alloys which preferentially may be used include AISI 302, AISI 308, AISI 316, and AISI 347. Casings of the foregoing and like-behaving alloys are used in the cold worked condition, without annealing. The select alloys have a desirable combination of formability, corrosion resistance, and strength. In their annealed condition the alloys are not magnetic; when cold worked during casing fabrication they are magnetic. What comprises a magnetic casing is described below in connection with Table 1. In the preferred materials, a deformation-induced martensite (a ferromagnetic phase) is present when the material is cold worked and not-annealed; and that makes the material advantageously attracted by a common magnet. Preferred casing sleeve embodiments are formed of alloys that are in a special class and that are worked in a special way. For example, the austenitic stainless steel, AISI 316, as compared to AISI 304 steel, may not be magnetic when the casing is cold-worked to make a 9 mm casing as described herein. But the casing will be magnetic when AISI 316 steel is worked more severely, such as to form a 7.62 mm casing as described herein, or to form some other casing. In contrast, when casings are made of a stainless steel of the AISI 400 series which is ferritic, the casing will be magnetic regardless of extent of cold working or the presence of martensite.
When casings made of a preferred magnetic austenitic metal are discharged from an automatic or semi-automatic weapon and are scattered about on the ground, the used casings may be retrieved by sweeping an area with a permanent magnet or common electromagnet. Compare, brass, aluminum or non-metal casings cannot be so retrieved.
Working of the AISI 304 alloy also hardens it and increases its ultimate strength, enabling a lighter wall thickness in the sleeve than when the alloy is not cold worked. Preferably, the AISI 304 sleeve material is at least “one-quarter hard”, wherein it has a hardness of at least about Rockwell C (“Rc”) 30 and an associated ultimate tensile strength of about 125,000 psi (pounds per square inch)(6×106 N/m2). That compares with the Rockwell B 83-92 hardness and about 75,000 psi (3.6×106 N/m2) ultimate tensile strength of a common annealed wrought bar or strip of AISI 304 material. More preferably, AISI 304 material is worked so that the hardness is greater than about Rc 40 and the ultimate tensile strength is in excess of 150,000 psi (7.2×106 N/m2).
Preferably, the sleeve is formed in an eyelet machine (transfer press), starting with a flat disk of steel. The disk is sequentially worked to change shape for a 9 mm casing as illustrated by the steps (a) to (e) in
Table 1 shows the magnetic properties at each stage and the hardness distribution at the final stage (e). It is seen that with progressive working, the permeability (loosely “the magnetization”) increased, measured in Mu. Likewise, it is seen that hardness increased significantly at midpoint M and the mouth end E. The hardness in HVN (Vickers Hardness Number using a 200 gm load) is highest at the mouth end, being more than 400 HVN. As is well known, increased hardness is associated with increased yield/ultimate strength, and that property is desirable where the sleeve wall has higher stresses, namely at the cylindrical portion, compared to the nipple.
Preferably, the sleeve of an invention casing is an austenitic stainless steel having a permeability which is at least 2 Mu, more preferably at least 3 Mu. In this application, a steel having such at least 2 Mu property is said to be magnetic. Casings comprised of a sleeve in such magnetic condition can be attracted by a permanent magnet or electromagnet; that is quite useful for purposes of retrieving and/or handling used casings.
The degree of magnetism, namely permeability (more properly relative permeability), of a casing can be measured in Mu units in accord with standard ASTM A342-Method No. 6. Use may be made of a measuring device called The Severn Gage (Severn Engineering Co., Inc., Auburn, Ala., U.S.).
The cylindrical portion E of the sleeve, which extends to the mouth becomes most hard and correspondingly magnetic. The bulkhead also is strong and magnetic. In comparison, the nipple portion of the sleeve is desirably less worked and less hardened and that facilitates its press fit engagement with the base and its capturing within the base by means of a lip. The small diameter of the nipple means stresses for any given internal pressure are lower than in the cylindrical portion of the sleeve. Also, being small and buried within the base, a nipple would contribute little to attraction of a casing to a magnetic pickup tool. Since it is less hard, the nipple terminal end more amenable to being flared radially outwardly and the desired good sealing contact may be better achieved. Cold-working to make the flared lip increases hardness and permeability of the lip portion, but does not change the corresponding properties of the lengthwise nipple portion that runs toward the bulkhead from the lip within passageway 156, 256, in particular, that portion which is in vicinity of void 43 in
Thus an embodiment of casing and sleeve is a combination which comprises a sleeve having less permeability and hardness in the nipple where it runs from the lip and the shoulder of the primer recess to the bulkhead that does the sleeve have in at the bulkhead and mouth end.
The base may be formed by stamping, pressing, or machining, less preferably by casting. The base is preferably made of wrought aluminum alloy, preferably alloy wrought 7075 alloy in T6 temper condition. That alloy is of high strength, sufficient to hold the primer and sufficient to endure the forces of the manufacturing process during which the nipple is deformed. An aluminum base may be anodized and dyed for color coding, to demark different types of cartridges. Alternatively, an aluminum alloy base may be coated with electroless nickel phosphorous metal. An exemplary aluminum alloy base will have a Rockwell B hardness in the range 70 to 98. The base has strength sufficient to sustain deforming of the nipple and forces imposed by the breech block. In still another alternative, the base is made of a steel alloy, such as AISI 304 or AISI 316 or a low carbon steel.
In a concept of the present invention, the sleeve cylindrical portion including the mouth has the highest strength and hardness, the bulk of the nipple with the passageway of the base has lesser strength and hardness, and the base has the lowest hardness. This combination is advantageous for reasons in part stated above, and further because the softer base lessens wear or decreased life of the firearm parts which grip and eject cartridges/casings, compared for instance to a steel base, or to a prior art steel casing.
In the generality of the invention, a base may alternatively be made of other metal, such as cartridge brass, other brasses, and cast zinc base alloys, which metals may be less hard than the sleeve material. In still other embodiments of the invention, iron alloys or ceramics may be used for the base. A steel (iron alloy) is described below.
A casing 520 is made in essentially the same way as previously described, with the addition of a “cone-forming” step, wherein after the straight cylindrical wall section at the mouth end is formed, its outer end is reduced in diameter by inward deformation to create portion 523.
The pressure of gas within the casing during firing of a bullet of a typical NATO 7.62X51 round is substantially higher than the pressure associated with firing a bullet from a 9 mm round, with which the description above was principally concerned. When an experimental NATO 7.62X51 casing is configured consistent with the arrangement of bulkhead and base surface shown in
Furthermore, as is commonly the situation, when the casing is used in rounds that are fired from a high speed repeating fire arm, the casing is pulled out of the chamber by an extraction mechanism that comprises a single arm grip. The pulling force of the grip may be high because the expanded sleeve wall of the casing may not have relaxed from being expanded, given a high rate of firing. The grip can produce a significant eccentric force on the base, urging it to cant relative to the centerline C and the length axis of the nipple; and as a result there may be some unwanted permanent deformation and small separation of the sleeve/bulkhead outer edge and mating base outer surface.
The embodiment of casing 520 that is illustrated by
Surface 536 of the distal or second end of base 524 (that end which faces bulkhead 526 of sleeve 522) preferably has a contour that lessens the chances of failure under high deflagration pressures. Surface 536 comprises, nearest the passageway 556, inner annular flat portion 537; next, in the radially-outward direction is conical section 535; next, outer annular flat portion 539. Portion 539 terminates at a radially-outer base edge that is chamfered. The annular portions 537, 539 are preferably substantially perpendicular to the lengthwise axis C; alternative embodiments may have slight incline angles. The conical surface 535 has an angle AA of preferably 18 degrees to a plane perpendicular to the length axis C. In other embodiments angle AA may range from 5 to 25 degrees. (Conical surface 535 and any mating conical surface of the bulkhead are simply referred to as “conical” though they are technically frusto-conical sections.) In other embodiments of the invention the conical surface 535 may be curved in the lengthwise axis direction instead of being straight as pictured, and within the scope of claims that configuration should be characterized as a conical section.
Bulkhead 526 generally fits intimately with or contacts base distal surface 536, but for the presence of a wave 550. Bulkhead 526 comprises an inner annular portion 541 that mates with base surface 537; an outer annular portion 543 that mates with base surface 539; and a conical portion that connects the annular portions and mates with base surface 535. The smaller diameter end of the bulkhead conical portion projects lengthwise away from the direction of mouth end of the sleeve and fits the conical surface portion 536 of the base, except where preferred wave 550 provides a circular depression in the bulkhead surface which faces base distal surface 536. Wave 550 defines, with the surface 536 of the second end of the base, void space 558. The wave has function and benefit like those waves previously described. There may be more than one wave, also as previously described. In other embodiments there may be no wave. It is felt that an advantage of having the annular portions attending the conical portion of the bulkhead is that it gives better assurance that the shape and thus the fit of the cone will not be compromised because of the curvature of the bulkhead where it transitions to either the cylindrical sleeve portion or the nipple. In casing embodiments where there may be different needs, the base second end (and the mating bulkhead) may have only one or none of an inner annular surface and an outer annular surface.
Consistent with what has been recited above, a NATO 7.62X51 cartridge may comprise a bulkhead with wave that mates with a base distal end surface that nominally is perpendicular to the lengthwise axis C, i.e., like the casings shown in
Experiments show improved performance with respect to containing high deflagration pressures for casing embodiments having features like those shown in
The inward facing curving surface of skirt 770 is shaped to mate with the curved edge 740 of sleeve 722. See
With any of the base-to-sleeve configurations described above, the case forming process described in connection with
A further casing improvement relates to the size and shape of the base of the casing and its cannelure feature. Referring again to casing 520, the circumscribing cannelure 546 which is shown in
A casing embodiment of the present invention is characterized by a cannelure that, in lengthwise centerline cross section of the base, has a mostly continuous curve shape. That compares with a prior art cannelure defined by only cylindrical and frusto-conical surfaces. Cannelure 646 in
Experiments have shown that only when the cannelure is shaped as just described is the necessary good strength and functionality obtained in a casing. The base volume is reduced, making feasible the use of a heavy-but-strong alloy (e.g. an iron alloy) compared to a copper base alloy or a light metal alloy (e.g. an aluminum alloy). When the size of the cannelure is increased and diameter of the cannelure is reduced, as described below, that makes feasible a process wherein a base is formed from highly machinable but not-so-strong steel and the base is thereafter strengthened.
A prior art configuration of cannelure 546 for a NATO 7.62X51 casing has a 0.469 inch (1.19 mm) outside diameter DW and a 0.403 inch (1.02 mm) diameter DT of the deepest portion of the cylindrical surface or groove-bottom. See
In this description, a “same-size base” is a hypothetical base which has the same dimensions as an exemplary base, but for the absence of a cannelure. The volume of a cannelure is the volume of an imaginary solid having an interior surface with the shape of the cannelure and an outside cylindrical surface, the diameter of which is that of the base portion near the sleeve where there is no cannelure surface. That cannelure volume is fractionally compared to the volume of a hypothetical same-size base. If a base has a flange portion with an outside diameter greater than the diameter of the sleeve, such greater diameter flange portion would be ignored in any parametric comparison.
In an exemplary base 624 of the present invention, the outside diameter DWW is about 0.469 inch and the deepest groove portion diameter DTT is about 0.300 inch (7.6 mm). See
Presently, experiments have been carried out with casing with bases made of steel material having an estimated yield strength of 120,000 to 140,000 pounds per square inch (about 827,000 to 965,000 kiloNewtons per square meter (kN/sq m)). The bases have been formed by the methods described below.
A cannelure embodiment of the present invention has a diameter DTT that is between about 60 to about 80 percent of diameter DWW and a volume that is between about 20 and about 43 percent of a same-size base having no cannelure. An invention embodiment cannelure may have as much as about 3 times greater volume than a cannelure having the size taught by the prior art for a NATO 7.62X51 casing. The invention cannelure may be used in bases of other size firearm rounds and in bases made of other materials than the kind of material preferred for a NATO 7.62X51 round; and may be used in bases which have a second/distal end surface which is other than conical.
To recapitulate, in embodiments of the present invention, a two piece casing comprises a base having a cannelure which comprises one or more of:
And embodiments of the invention comprise a two-piece casing comprised of a base and associated sleeve bulkhead, each having mating dished or conical portions, preferably with one or both an inner annular portion and an outer annular portion; and an optional wave.
The features of the
A NATO 7.62X51 round is preferably made of an iron alloy, compared to an aluminum alloy which has been described above for 9 mm casings. An iron alloy has a benefit of being resistant to errant metal ignition. For machinability, bases may be machined from AISI 12L14 steel (a commercial leaded steel having up to about 0.15 weight percent carbon) or another low carbon steel. Such steels lack sufficient carbon to be significant hardenable by heat treatment. Higher carbon steel or alloy steels which are hardenable could be used for their high strengths, but such metals have a disadvantage of comparatively low machinability, raising cost of fabrication. Bases will typically be machined from bar stock using an automatic screw machine.
In a manufacturing method of the present invention, there is a desirable synergy and criticality in making a base from a high machinability low carbon steel, forming a large cannelure like that described above to reduce section thickness, and then diffusing carbon into the metal of the base (carburizing), and then heat treating the base. Optionally, there may also be plating or other surface protection provided in the finished product.
Normally, carburizing (typically heating to diffuse carbon from active agents placed in proximity the surface of a metal part) is thought of as being useful for imparting surface hardness and wear resistance to a component, while retaining ductility and toughness in the core region. Since casings most often have a onetime use (and even if they are reloaded, they have limited number of re-uses), there would not be good reason to provide surface hardness to the base of a casing—the amount of wear being minimal.
In the present invention, the large cannelure and resultant small metal thicknesses in a base enable the carburizing process to be employed to convert the material of the base into a material which is responsive to heat treatment and resultant raising of tensile strength. And otherwise insufficient strength base material is thus converted into one that has strength sufficient to resist failure under the high pressures and forces associated with deflagration of gunpowder.
In the invention, carburizing attains a desirable concentration of carbon—an exemplary aim being about 0.4-0.5 weight percent carbon in the surface regions and near surface regions—which concentration is sufficient to enabling subsequent heat treatment, hardening, and strength increase. Thus a base with an exemplary large volume and deep depth cannelure is able to resist the forces of deflagration. In an exemplary practice of the invention, carbon diffuses to a depth of about 0.020 to about 0.040 inch (0.5 to 1.1 mm). Carbon diffuses into the base structure from the internal passageway as well. As a result of having the passageway and deep cannelure, a large fraction of the base is able to have sufficient carbon addition to be strengthened by heat treating. The surface diffusion process which characterizes carburizing provides a carbon concentration gradient, with the highest amount of carbon at the surface and the near-surface regions, and the least amount of carbon at portions most distant from any surface. After carburizing, followed by austentizing, followed by quenching, an exemplary base within which the metal is AISI 12L14 steel or another low carbon steel will have in the surface and near-surface regions a hardness of about 30-35 Rockwell C and an associated yield strength estimated at 120,000 to 140,000 pounds per square inch (about 827,000 to 965,000 kN/sq m). In interior portions distant from a surface, the hardness may be 20 Rockwell C.
The present invention includes a round (also called a shell or a cartridge) which comprises a casing having the new features which are described herein. In particular, a round is formed by pressing into place a primer in the recess of the base of casing, putting gunpowder into the concavity of the sleeve through the mouth end, and pressing and crimping a bullet into the mouth of the sleeve.
The present invention also includes the method of making a casing and a cartridge having the features described herein using the methods which have been described. A casing may be assembled from a sleeve and base by using automated machinery which mates the two pieces with each other and using (a) tooling that fits within the mouth of the sleeve and presses on the nipple and adjacent bulkhead while the base is being held, to force the nipple into the passageway of the base so the outer edge of the sleeve/bulkhead is either in contact with the face of the base or intimately close; and using (b) tooling that fits within the primer recess and presses axially on the terminal end of the nipple to flare the end radially outwardly and form a lip which presses against the shoulder at the bottom of the recess, where the lip preferably has an annular curved surface. Thereafter, to form a cartridge, in step (c) a primer is pressed into the recess at the end of the base so the legs of the primer anvil contact or are very close to the surface of the lip; in step (d) gunpowder is put into the concavity of the sleeve; and in step (e) a bullet is pressed into the mouth of the sleeve and the mouth is preferably crimped onto the bullet. When the casing is intended for a full powered casing such as a NATO 7.62×51 mm round, the sleeve portion near the sleeve mouth will be “coned” so there is a reduced diameter cylindrical portion, preferably after the foregoing step (a).
The unique features of the sleeve and base provide the invention with surprising advantage. A casing/cartridge is provided with a desirable combination of lower weight, lower cost and higher performance than prior art casings. At the same time the casings/cartridges generally have durability during handling and the capability for reloading. While the invention has been described in terms of small caliber cartridges, the invention may be applied to large caliber shells.
The invention, with explicit and implicit variations and advantages, has been described and illustrated with respect to several embodiments. Those embodiments should be considered illustrative and not restrictive. Any use of words which relate to the orientation of an article pictured in space are for facilitating comprehension and should not be limiting should an article be oriented differently. Any use of words such as “preferred” and variations thereof suggest a feature or combination which is desirable, but which is not necessarily mandatory. Thus, embodiments lacking any such preferred feature or combination may be within the scope of the claims which follow. Persons skilled in the art may make various changes in form and detail of the invention embodiments which are described, without departing from the spirit and scope of the claimed invention.
This application is a divisional application of application Ser. No. 16/383,633, filed Apr. 14, 2019, now U.S. Pat. No. 10,697,774, which is a continuation in part of application Ser. No. 15/221,530 filed Jul. 27, 2016, now U.S. Pat. No. 10,260,847.
| Number | Name | Date | Kind |
|---|---|---|---|
| 43851 | Howe | Aug 1864 | A |
| 2904873 | Hild | Sep 1959 | A |
| 3874294 | Hale | Apr 1975 | A |
| 4041868 | Rayle | Aug 1977 | A |
| 4122933 | Starzyk | Oct 1978 | A |
| 9939236 | Drobockyi | Apr 2018 | B2 |
| 10260847 | Viggiano | Apr 2019 | B2 |
| 20060075919 | Wiley | Apr 2006 | A1 |
| 20170030690 | Viggiano | Feb 2017 | A1 |
| 20170030692 | Drobockyi | Feb 2017 | A1 |
| 20180321020 | Evans | Nov 2018 | A1 |
| Entry |
|---|
| PCT International Search Report, Application PCT/US19/27420, dated Sep. 3, 2019, 20 pages. |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16383633 | Apr 2019 | US |
| Child | 16916825 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15221530 | Jul 2016 | US |
| Child | 16383633 | US |
