US3422761A

US3422761A - Shotgun cartridges

Info

Publication number: US3422761A
Application number: US578530A
Authority: US
Inventors: Peter John Whitmore
Original assignee: Imperial Metal Industries Kynoch Ltd
Current assignee: Imperial Metal Industries Kynoch Ltd
Priority date: 1965-09-24
Filing date: 1966-09-12
Publication date: 1969-01-21
Anticipated expiration: 1986-01-21
Also published as: ES331569A1; GB1101856A; DE1578158A1; SE312745B; AT277818B; BE687341A; NL6613472A; NO119067B

Description

P. J. WHITMORE SHOTGUN CARTRIDGES Filed Sept. l2, 1966 Jan. 2, w69

i5 nl ,2.1; f,

PHG. 3..

3,422,761 SHOTGUN CARTRIDGES Peter Jolm Whitmore, Sutton Coldiield, England, assignor to Imperial Metal Industries (Kynoch) Limited, Birmingham, Warwickshire, England, a corporation of Great Britain Filed Sept. 12, 1966, Ser. No. 578,530 Claims priority, application Great Britain, Sept. 24, 1965,

40,739/ 65 U.S. Cl. 102-42 9 Claims Int. Cl. F42b 7/ 00 ABSTRACT OF THE DISCLOSURE This invention relates to shotgun cartridges.

According to the present invention, a shotgun cartridge comprises a cup-like head, a tubular body of which one end is ca-pable of being fitted into the head in a manner such that the body is ejectable from the head upon the cartridge being fired, means for forcing the wall of said one end into sealing engagement with the head on ring tbe cartridge so that the gases produced by ignition of the propellant eject the tubular body from the head, a charge of shot contained in the other end of the tubular body, and a matrix of frangible material in which is ernbcdded the charge of shot and which is strong enough to bind the shot charge together and to the wall of the tubular body during normal handling, but is shatterable when the cartridge is fired.

A convenient matrix material comprises a rigid plastics foam, for example, polyurethane. When such a material is used, the individual shot are held in place by a multiplicity of thin webs of the plastics material which possess sufficient strength and resilience to withstand the forces likely to be imposed on them during handling, c g. during assembly of the cartridge and on loading it into a gun, but when the webs are simultaneously subjected to the considerable impact attendant on firing the cartridge, they are shattered and release the charge of shot, so that it is free to emerge from the tubular body 'when it leaves the barrel of the gun. The separation of the shot from the encircling webs of plastics material is enhanced by the great disparity between the densities of the shot and the plastics material.

In order to assist projection of the shot from the tubular body, it may be desirable to provide the -wall of the tubular body with longitudinal slits wbich extend from the shot charge end along part of its length. These slits divide that part of the body wall into segments, but they do not weaken the wall of the assembled body since their edges are initially bonded together by the matrix material. However, when the cartridge has been fired the matrix is shattered and the slit end of the tubular body is peeled backwards by ywind resistance as it emerges from the barrel of the gun thus assisting projection of the shot from the tubular body. The matrix material preferably extends through that part of the tubular body which is occupied by the shot charge, but it may be confined to that part of the charge next to the mouth of thelv tube, to form a frangible closure.

nited States Patent Since the shot charge is isolated from the gun barrel by the tubular body, either lead or cast iron shot may be used, since neither leading nor scoring of the surface of the bore of the barrel will be caused.

The tubular body may be made from a variety of light, resilient materials, such as plastics, rolled paper or aluminium alloys: but plastics materials, e.g. polyethylene, are preferred as they may be produced accurately and economically on a large scale by injection moulding, or the like, are virtually impervious to moisture and are neither corrosive nor corrodible. The rear lwalls of the tubular body must possess suicient strength and resilience to allo-w the body to be pressed into gas-tight contact with the wall of the head on firing and, later, with the wall of the gun barrel.

The sealing means is completed by some form of obturation of the bore of the tubular body; this may conveniently comprise a gas-tight partition located intermediate the ends of the tubular body so as to divide it into two open-ended chambers. Thus, when the cartridge is fired the gases produced will be trapped in the sealed space defined by the partition, the inner wall of one end of the tubular body and the inner surface of the head, so that the gas press-ure finally builds up sufficiently to eject the tubular body from the head. The lwall of the tubular body will then be forced into sealing engagement with the wall of the gun barrel so that the gases will propel the tubular body through it.

The partition may take the form of a separate disc-like member, bonded to the inner fwall of the tubular body, lbut is preferably formed integrally with it. For example, when a plastics material is used, the tubular body and partition may be injection moulded in a single operation. Suc-h a construction may also be formed as an impact extrusion from, say, aluminium.

The tightness of the fit of the tubular body in the head should be such that the body is retained in the head under normal handling conditions, but that the resistance to ejection from the bead on firing should be sufficient to produce the desired ballistic performance but should not be so great as to present a risk of the wall of the body being ruptured in the process. The tightness of the fit must be carefully controlled to balance the opposed requirements of build-up of gas pressure and ease of ejection, but optimum conditions may be readily established in any particular design by simple experiments.

The ejection pressure will normally be greater than that resulting from the mechanical pressure between the head of the tubular body, -because 0f the added resistance generated by the sealing action of the wall of the tubular body against the wall of the head. Thus it is possible to make use of a tubular body and head having plain walls which allow the one to be a push-fit within the other, but such arrangement may require unduly restrictive tolerances on the dimensions of the two members. This restriction may be lessened or obviated by providing co-operating grooves and notches or the like on the body and/or head so that the gas pressure must exceed a designed threshold value before the body is released from the head. Alternatively, the lip of the head wall may be turned inwardly to grip the tubular body resiliently.

The head may be made of plastics or metal, but is preferably made of metal as in a traditional cartridge. However, the depth of the head is sufficient to allow releasable grip to be incorporated between head and body. Since, in cartridges according to the invention, the cartridge head may be made to outlast several tubular bodies, it is economically feasible to make it of a more robust construction than has been the practice in fixed head cartridges; for example, it may consist of a zincbase die casting or even be machined from brass stock. Using either of these methods it is a simple matter to provide an annular ridge or the like on the inner wall of the head which will co-operate with the tubular body and improve the grip. Cartridge heads according to the invention which are produced by the more traditional cupping and drawing processes may have their lips turned inwardly to grip the tubular body or may have an annular groove formed in their outer wall so as to raise a corresponding annular ridge on the inner wall.

Cartridges according to the invention may be provided with traditional detonators and propellant charges. The detonator most conveniently takes the form of a percussion cap fitted into a central cavity in the head in well-known manner, the propellant charge being located within one end of the tubular body when the cartridge is assembled. Alternatively, the propellant charge may be ignited electrically, e.g. by capacity discharge between electrodes projecting through the head into the space occupied by the charge.

Some or all of what might be termed the disposable elements of the cartridge may be incorporated in a single unit, hereinafter referred to as a refill unit. Such a unit must include the tubular body and bonded shot charge, but, preferably the propellant charge may be incorporated in that end of the tubular body intended to be fitted into the head. When this is done, the propellant charge may be retained in the tube by a closure disc or even bonded in place, e.g. by using a castable propellant mixture. The only restriction on such expedients is that the closure should be penetrable by the flash `from the detonator to allow the powder charge to be ignited thereby. This may be accomplished by using a combustible material for the closure or, when a non-combustible I closure disc is used, by providing means to pierce the disc when the refill is pushed home into the head. Should the propellant charge be omitted from the refill unit, it may be loaded into the head before the said unit is fitted.

In order that the invention may be more clearly understood, it will be described, by way of example only, with reference to the accompanying drawings, in which:

FIGURES 1 and 2 are axial sections of two forms of cartridge according to the invention, and

FIGURES 3 and 4 are axial sections of two forms of refill unit.

Like reference numerals refer to like parts.

Referring to FIGURES 1 and 2, a tubular body 1 is injection moulded from low-density polyethylene having a melt flow index of 20, and comprises two tubular chambers 2, 3 separated by an integral partition 4. One end of body 1 is fitted within a cup-like head 5; the other end is provided with longitudinal slits 2a Which extend towards the partition 4 and sever that end of the tube into segments.

The chamber 2 of the tubular body 1 is provided with a wad 6 of compressed fibre, the remainder of the chamber being filled by a charge of lead shot 7 embedded in a matrix of rigid polurethane foam 8. The chamber 3 contains a charge 9 of granular double-base propellant.

The foam 8 was formed in situ by mixing three liquid ingredients, a polyether resin, Daltolac 41 (registered trademark) a di-isocyanatodiphenylmethane composition, Suprasec D (registered trade mark) and trichlorofluormethane, Arcton 11 (registered trademark) in the following proportions:

Parts (by weight) Daltolac 41 100 Suprasec D 185 Arcton 11 3() In an alternative method of forming the foam in situ, 137 parts by weight of Daltolac 6202 (registered trade mark) di-isocyanatodiphenylmethane composition were mixed with 178 parts of Suprasec DN (registered trade mark).

The above ingredients are introduced into the chamber 2 of the tubular body 1 in rapid succession, immediately before loading the charge of shot 7. A rigid plate (not shown), coated with a silicone release agent, are then pressed against the mouth of the chamber 2 of the tubular body 1 to prevent overflow of the foam which is formed, and to ensure that a coherent, flat top layer is formed on the matrix 8.

The head 5 shown in FIGURE 1 comprises a deepdrawn brass cup, provided with an integrally formed central cap chamber 10 having a flash hole 20. The cap chamber 10 accommodates a detonator cap 11 and an anvil 12 of a type commonly used in traditional shotgun cartridges. An annular fibre wad 13 is located between the wall of the head S and the cap chamber 10, and serves to strengthen the head 5. A raised chamfered edge 13a of the wad 13 serves to locate the lower end 3 of the tubular body 1, assists in sealing the propellant cavity, and prevents particles of propellant from entering the annular cavity between the head 5 and the body 1. The lip 14 of the head 5 is turned inwardly after insertion of the tubular body 1 to increase the grip between the head 5 and the body.

The head 5 shown in FIGURE 2 consists of a zincbase die casting provided with a central cavity 15 and a flash hole 20 to accommodate a cap and anvil of the same type as shown in FIGURE 1. Heads 5 as shown in FIGURE l or FIGURE 2 are provided with ejector rims 16 to enable the used head to be ejected from the breech of the shotgun.

On firing a cartridge of the kind shown in FIGURE l or FIGURE 2, the cap 11 is detonated and the flash ignites the powder charge 9. The gases produced by ignition of the propellant 9 force the wall of the chamber 3 of the body 1 against the Wall of the head 5, thus forming a gas seal. This causes the gas pressure to build up in the chamber 3 until eventually the body 1 is ejected from the head S. The shock produced on firing the cartridge shatters the polyurethane foam 8 and frees shot 7 from each other and from the wall of the chamber 2. The separated charge of shot 7 is then carried through the barrel of the gun by the momentum of the body 1 until it emerges from the mouth of the barrel, when the segments of the wall of chamber 2 defined by slits 2a are peeled back by air resistance causing the shot 7 to quickly outstrip the body 1 by virtue of their greater density and smaller air resistance.

Referring now to FIGURES 3 and 4, the refill units illustrated therein comprise tubular bodies 1 having charnbers 2 and 3 filled as previously described. However, since the refill units are intended to be self-contained, the powder charges 9 are held in place by closure discs 17 cut from nitrocellulose sheet. The discs 17 are either retained in position by an annular shoulder 18, on the inner wall of the chamber 3, as shown in FIGURE 3, or are formed with an upturned rim 19 which is then bonded to the outer wall of the chamber 3. It will be appreciated that, by making the closure disc 17 from a highly inflammable material, such as nitrocellulose, it serves to retain the propellant charge in position but does not insulate it from the effects of the detonator flash on firing the cartridge. Should it be desired to avoid the use of inflammable materials in the closure disc 17, it may be formed from a noninflammable material, such as aluminium foil, provided that the head has means to pierce the disc 17 when the refill unit is pushed home in the head 5, and thus form a flash hole. The piercing means may conveniently take the form of a sharp annular rim about the upper edge of the cap chamber 10 in the head 5, for. example.

The use of a cartridge incorporating a refill unit as described above, possesses distinct advantages if the cartridges are to be re-loaded. The operation merely comprises de-capping the head, re-capping and pushing home a new reiill unit, This procedure obviates the steps of measuring out the charges of shot and powder, incorporating them in the correct order in a spent cartridge tube and then reclosing the open end of the tube in some way.

In the embodiments described above, a iibre wad 6 is located between the shot 7 and the partition 4. Since this wad is compressible, it allows the shot 7 to be forced below the mouth of the chamber 2 while body 1 is moving through the gun barrel. Because of this, the slits 2a are essential to obtain good ballistic performance. However, if a non-compressible light-weight wad is used, for example, a thick plastics disc supported by deep radial ribs or of honeycomb-sandwich construction, the slits 2a may be dispensed with.

The methods of forming the foamed plastics matrix described above is by way of example only. Other ingredients and proportions of ingredients will be obvious to those skilled in the art, eg. making use of externally applied foaming agents with or without the application of heat.

Furthermore, foam-forming ingredients such as those described in the examples, may be ydispensed by a spray gun or the like. By use of this, in conjunction with a suitable metering unit, the ingredients can be intimately mixed in the correct proportions immediately prior to delivery of material to the point at which foaming is to take place. Thus, on an automatic cartridge loading machine, the body is indexed first to a foam dispensing station, it then passes rapidly to a shot loading station, finally arriving at a finishing station at which the rigid plate could be pressed against the mouth of chamber 2 to prevent overflow of the foam.

I claim:

1. A shotgun cartridge comprising a cup-like head and a tubular body, the body deiining at one end a first chamber and at the other end a second chamber, the irst and second chambers being separated from one another by an internal partition, integral with the body, and said one end of the body being iitted into the head in a manner such that upon the cartridge being tired by ignition of a propellant contained within the first chamber at said one end, the gas pressure produced forces the wall of said one end into engagement with the interior of the head to form a gas seal and thrusts against the partition to eject the tubular body from the head, the second chamber of the body containing a matrix of frangible material which has a charge of shot embedded therein, the matrix being strong enough and forming a sufficiently strong bond with the wall of the tubular body to retain the shot charge in position within the body during normal handling, but being shatterable when the cartridge is tired.

2. A shotgun cartridge according to claim 1, characterized in that the matrix material comprises a rigid plastics foam.

3. A shotgun cartridge according to claim 1, characterized in that the wall of the Itubular body is divided into segments over part of its length by longitudinal slits which extend from the shot charge end of the body, the edges of the slits being initially bonded together by the matrix material.

4. A reiill unit for a shotgun cartridge comprising a tubular body having at one end a first chamber and at the other end a second chamber, the first and second chambers being separated from one another by an internal partition integral with the body, said one end of the body being capable of being ejectably iitted into a head of a cartridge, the second chamber at said other end of the body containing a matrix of frangible material which has a charge of shot embedded therein, and the matrix being strong enough and forming a suiiiciently strong bond with the wall of the tubular body to retain the shot charge in position within the body during normal handling, but being shatterable when the cartridge is tired.

5. A refill unit according to claim 4V characterized in that the matrix material comprises a rigid plas-tics foam.

6. A reiill unit according to claim 4, characterized in that 'the wall of the tubular body is divided into segments over part of its length by longitudinal slits which extend from the shot charge end of the body, the edges of the slits being initially bonded together by the matrix material.

7. A refill unit according to claim 4 characterized in that a propellant charge is retained within that end of the tubular body which is intended to be iitted into the cartridge head.

8. A refill unit as in claim 4 wherein said first chamber contains a propellant and wherein said chamber is closed with a closure disc of highly inammable material.

9. A shotgun cartridge comprising: a cup-like head; a tubular body having at one end a first axially-facing chamber containing a propellant and having at the other end a second chamber containing a charge of shot, said chambers being separated from one another by an internal partition which is integral with said body, said one end being iitted into said head in a manner such that upon tiring of the cartridge by ignition of said propellant the gas pressure produced forces the wall of said one end into engagement with the interior of the head to form a gas seal and thrusts against said partition to eject said tubular body from said head, said other end of said tubular body being disposed outside said head and terminating in an annular wall which is free of a shot-retaining closure, the shot being retained in said second chamber solely by being embedded in a body of frangible material which has suiiicient strength to bind the shot together and to said annular wall during normal handling and which is shatterable when the cartridge is tired.

References Cited UNITED STATES PATENTS 3,092,026 6/ 1963 Williams et al 102-42 3,104,523 9/1963 ODonnell 60-35.6 3,234,877 2/1966 Herter 102-95 3,309,994 3/1967 Lage 102-42 ROBERT E. STAHL, Primary Examiner.