Ammunition cartridge

A blank or live ammunition cartridge suitable for rifles or guns and including a cartridge case made of a plastics material and comprising a metal bottom insert; the metal bottom insert is part of an integral element comprising said bottom insert firmly anchored in a plastics sleeve, said integral element being inserted into the lower or bottom end of the cartridge case. A method for manufacturing an ammunition cartridge by forming a metal bottom insert from a metal sheet by deep-drawing; combining said metal bottom insert with a plastics sleeve so as to produce an integral structure; and inserting such integral structure into the bottom end of a plastics cartridge case.

BACKGROUND OF THE INVENTION 
This invention relates to improvements in the ammunition art and, 
specifically, to ammunition cartridges of the type having a plastics 
cartridge case, i.e. a case that is made, at least in a predominant 
portion, of a synthetic polymer composition and where the lower end 
portion of the cartridge case is provided with a bottom insert made of a 
metal. The term "lower end" relates to that end of the cartridge case 
which is opposed to the projectile-bearing or projectile imitation-bearing 
end of the cartridge. 
Cartridges of this type are known and have been disclosed, for instance, in 
Swiss Patent 326,592. Cartridges of this type are used in large quantities 
as blank rifle cartridges in which the head end of the cartridge case 
continues into the imitation shape of a plastics projectile which 
constitutes an integral part of the cartridge case and is furnished at its 
upper end with a notch or similarly formed predetermined rupture point. 
The use of a plastics material for ammunition cartridge cases offers 
considerable advantages over usual metal cases in regard to cost and 
production, but necessitates a bottom insert of metal which is suitable as 
a groove or edge for engaging the usual cartridge extractor and ejector 
and for receiving and holding a detonator or percussion cap. 
A prior art bottom insert of this type is a generally cylindrically shaped, 
solid metal component having an opening for receiving the detonator cap, 
an external groove for interaction with the cartridge extractor, and a 
generally cylindrical upper end portion with its external surface grooved 
in the manner of a dowel for anchoring inside the wall of a plastics 
cartridge case. Generally, such bottom inserts are made from aluminum by 
machining as relatively large thicknesses of material are required in the 
cartridge bottom. Thus, production of conventional all-metal bottom 
inserts for plastics cartridges tends to be relatively costly both in view 
of the comparatively large mass of metal required and the costs of 
producing the inserts by conventional machining techniques. Insertion of 
such metal inserts into a plastics cartridge case can present problems 
such as ruptures of the walls of the plastics cartridge case. Further 
problems in connection with ammunition cartridges of the type having a 
plastics case for blank cartridges or projectile-bearing cartridges are 
encountered in regard to the projectile-like end portion or the connection 
of the projectile and the plastics cartridge case. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, it is the main general object of this invention to provide for 
improvements in connection with blank or live rifle and gun ammunition 
cartridges of the type having a plastics cartridge case. 
An important specific object is a novel type of insert for ammunition 
cartridges having a cartridge case made of a plastics material so as to 
decrease both the amount of metal used for the insert and the costs of 
producing the inserts. 
Another object is an improvement of structure and and function of blank and 
live ammunition rifle or gun cartridges that have a cartridge case made of 
a plastics material. 
Yet another object is an improved method of producing bottom inserts for 
ammunition cartridge cases made of a plastics material. 
Other objects will become apparent as the specification proceeds. 
It has been found that the above and further objects can be achieved 
according to the invention by means of a novel cartridge bottom insert 
that includes a metal bottom element integrally connected to a plastics 
sleeve element, and by certain modifications of the cartridge case with 
regard to the wall structure and the projectile imitation or 
projectile-bearing end of the ammunition cartridge. 
BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS 
According to a first general embodiment, this invention provides for an 
ammunition cartridge suitable as blank or live ammunition for rifles, said 
cartridge comprising a plastics cartridge case, i.e. a rifle or gun case 
consisting, at least in a predominant cartridge case wall portion, of a 
synthetic organic plastics material and having a lower end portion for 
receiving and holding a cartridge bottom insert; said cartridge bottom 
insert being a composite unit structure comprising a metal bottom element 
firmly secured in a plastics sleeve element. In general, the metal bottom 
element includes a chamber for receiving a detonator cap and is provided 
with two coaxial flange means or the like laterally projecting rims having 
different diameters and being interconnected by a tubular portion. 
Preferably, the metal bottom element is a shaped integral structure made 
of a sheet capable of being formed by deep-drawing while the plastics 
sleeve element is a generally rotationally symmetrical structure that 
surrounds the upper portion of the metal bottom element and comprises at 
least one means for engagement with an inner wall portion of the plastics 
cartridge case as well as an aperture connecting the detonator 
cap-receiving chamber of the metal bottom insert with a charge-receiving 
portion of the cartridge case. 
According to a second embodiment, the invention provides for a blank 
ammunition cartridge having a plastics cartridge case, the lower end 
portion of which is closed with a cartridge bottom insert and wherein the 
other end portion is shaped as an imitation projectile having a 
predetermined rupture point and an axial length of not more than 25% of 
the total axial length of said ammunition cartridge. 
According to a third embodiment, the invention provides for an ammunition 
cartridge having a plastics cartridge case provided with a cartridge 
bottom insert, wherein the inner wall of the cartridge case is provided 
with a plurality of elongated ribs for controlling volume and packing of 
the charge. 
In a preferred form of this third embodiment, an exterior wall portion of 
the plastics cartridge case is provided with a plurality of grooves for 
improved cartridge extractability from the cartridge chamber of a weapon. 
Preferably, the ribs and the grooves extend in a direction parallel to or 
helically around the longitudinal cartridge axis. 
According to a fourth embodiment, the invention provides for a live 
ammunition cartridge having a plastics case with a projectile protruding 
therefrom and a bond-control coating provided at the interface between the 
projectile and the plastics cartridge case. If the projectile is made of a 
metal, the bond-control coating is of the bond-improving type. For 
projectiles made of a plastics material, the bond-control coating is of 
the type that prevents an undesired interbonding of the plastics 
projectile and the plastics cartridge case. With either type of projectile 
a shoulder wall portion may be provided within the plastics case for 
defining the position of the projectile. 
Preferably, the plastics projectile has a lower projectile portion situated 
within the plastics case and having a larger diameter than the upper 
projectile portion that protrudes from the plastics case for improved 
projectile guidance upon firing without impeding introduction of the 
projectile-bearing cartridge into the cartridge chamber of a weapon. 
It is to be noted that the cartridge bottom insert of the second, third and 
fourth embodiment of the inventive ammunition cartridge preferably is the 
novel integral composite having a metal bottom element firmly anchored in 
a plastics sleeve element as specified in the first embodiment but a 
conventional all-metal insert may be used as well. 
According to a further embodiment, the invention provides for a method of 
manufacturing an ammunition cartridge with a plastics cartridge case 
having a lower end portion for receiving and holding a composite bottom 
insert including a metal bottom element and a plastics sleeve element by 
(a) forming an integral metal bottom element by deep-drawing of a metal 
sheet, (b) forming the composite bottom insert by anchoring the metal 
bottom element in the sleeve element, (c) providing a detonator cap within 
the metal bottom element, and (d) introducing the composite insert into 
the lower end portion of the plastics cartridge case. Preferably, the 
charge will be introduced into the cartridge case prior to introducing the 
bottom insert.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
In FIG. 1 the lower end portion of a plastics cartridge case 14 (indicated 
in broken lines with the central and upper cartridge case portions broken 
away for a simplified presentation) is closed by means of a composite 
cartridge bottom insert comprising the metal bottom element 10 that 
consists of two coaxial disc-like parts or annular flanges 101, 102 and of 
a tubular or hollow cylinder member 104 interconnecting the flanges. 
Flange 101 constitutes the actual cartridge bottom, the upper rim or edge 
portion of which is exposed for the engagement of a conventional cartridge 
extractor. Flanges 101, 102 and the interconnecting tubular member 104 
enclose a generally cylindrical chamber 100 for receiving and holding a 
conventional detonator or percussion cap, not shown in the drawings. 
Bottom element 10 is made of metal such as a light metal or alloy, e.g. 
aluminum or aluminum alloy, steel, brass or the like material capable of 
being processed by punching, pressing, deep-drawing and the like shaping 
methods for mass production purposes. The metal bottom element 10 is 
embedded or anchored in a rotationally symmetrical plastics sleeve element 
12 having a duct or passage 128 for connecting the interior or 
charge-bearing portion 141 of cartridge case 14 with chamber 100 of the 
metal bottom insert 10 so that actuation of a detonator cap in chamber 100 
will cause ignition of a charge provided in case 14. 
Sleeve 12 is of a plastics material, preferably a thermoplastic polymer 
composition which possesses a ball-pressure hardness (60 inch-ball), at 
ambient (15.degree.-30.degree. C.) temperature, of at least about 500 
kp/cm.sup.2 and a modulus of elasticity of at least about 
5.times.10.sup.-3 kp/cm.sup.2. Non-limiting examples of suitable 
thermoplastic materials include polyolefins such as polyethylene (high 
density type), polypropylene and the like, polyamides, polyacetals, 
polyesters, etc. In general, plastics of the type known to be suitable for 
manufacture of the cartridge case and including conventional additions 
such as pigments, dyes, fillers, stabilizers and the like can be used for 
the sleeve element of the inventive bottom insert. Duroplastics, i.e. 
cross-linked or thermoset polymers such as epoxy resins and the like may 
be used for the sleeve element, e.g. by casting or molding a 
duroplastically setting composition to form the sleeve element around the 
metal bottom element so as to form the composite unit. Sleeve elements of 
thermoplastic polymer compositions can be produced and shaped by 
conventional thermoplastics processing methods including injection 
moulding, compression moulding or other shaping processes with 
simultaneous anchoring of the metal element, e.g. by providing the latter 
in the sleeve-producing mold prior to introduction of the plastics 
material. In general, anchoring of the metal element in the plastics 
sleeve will be obtained by providing projections or grooves on the outer 
wall of cylinder 104 and/or by flange 102. Preferably, the laterally 
projecting portion of flange 102 constitutes the main anchoring component 
of the metal element but the lower face of flange 102 may be rounded as 
indicated in broken line 103. However, anchoring projections that have an 
analogous effect may be formed by continuous or interrupted beadings, 
ribs, webs or lengths of thread in the outer wall of cylinder 104. 
Alternatively, a firm connection between metal element 10 and plastics 
sleeve 12 can be obtained by screwing in, that is, by suitably threaded 
elements and without a plastic deformation of the sleeve material. 
The general shape of sleeve element 12 as illustrated in FIG. 1 is 
preferred but not critical as long as a sufficiently firm anchorage of 
metal element 10, on the one hand, and an adequate connection between the 
sleeve and the cartridge case 14, on the other hand, are ensured. Base 
portion 121 of sleeve 12 has a generally cylindrical shape, bears against 
the upper surface 105 of flange 101 and has a smaller outer diameter than 
flange 101 so as to accord with the desired depth of the extractor groove. 
Sleeve base 121 widens conically upwards and outwards to form abutment 126 
against which the cartridge case 14 bears. A number of beadings 124 is 
provided at the outer sleeve wall for securing the composite insert in the 
wall of case 14. 
The inventive composite bottom insert consisting of plastics sleeve 12 and 
metal element 10 firmly anchored therein is used to close the lower end of 
case 14 in the same manner as prior art all-metal bottom insert pieces. 
However, with the composite insert according to the invention, a 
comparatively non-problematic plastics-plastics connection is obtained 
between the plastics cartridge case and the plastics sleeve of the insert. 
It is surprising indeed that a major portion of the bottom insert of 
ammunition cartridges can be made of a plastics material without any 
disadvantage in regard to the suitability of such cartridge for use as 
blank or live ammunition even though the explosion pressure occuring upon 
firing of the charge acts upon the plastics sleeve of the insert rather 
than the metal bottom. As to the thickness of the plastics sleeve material 
above the metal bottom element, it is sufficient, in general, if the axial 
depth of aperture 128 and of the surrounding transition portion 123 is at 
least about as large as the axial depth of metal element 10. 
FIG. 2 shows a modification, preferred from its manufacturing aspects, of 
the metal constituent of the novel composite insert. This metal element is 
made from a circular disc of metal sheet, capable of being deep-drawn, for 
example steel, aluminum or brass, generally having the external dimensions 
and thickness of bottom plate 27. For producing the metal element shown in 
FIG. 2, the disc is punched or deep-drawn to form chamber 21 with an axial 
depth greater than that of the final chamber and then upsetting the 
chamber portion to the desired axial depth while simultaneously forming 
the external annular beading 23. Aperture 28 in upper wall portion 24 may 
already be present in the disc or may be formed during upsetting or later. 
Plastics sleeve 22 represented in a semi-diagrammatical manner for 
connection with plastics case 29 can be produced and shaped as explained 
in connection with FIG. 1, or have a somewhat simplified structure as 
shown in FIG. 2. The axial depth of abutment 226 is increased in a 
preferred embodiment so as to obtain an enlarged surface of direct contact 
between the plastics material of sleeve element 22 and the wall of the 
cartridge chamber of a weapon. 
A modified embodiment of the inventive cartridge bottom insert is 
illustrated in FIG. 3 showing the lower part of plastics sleeve 32 only as 
well as the bottom portion of a plastics cartridge case 34. The structure 
of the outer wall portion of sleeve 32 and the correspondingly 
intermeshing part of the inner wall of case 34 can be made in the manner 
illustrated in FIG. 1 and 2, or by any other means suitable for mutual 
connection. As both sleeve 32 and case 34 are made of a plastics material, 
various bonding methods for such connection will be apparent to the 
expert. 
Metal element 30 is made in a manner similar to that explained in 
connection with FIG. 2. An upwardly bent external rim 36 is provided 
having an end face 361 for interaction with the cartridge extractor and 
ejector mechanism of a weapon. Metal element 30 is anchored in plastics 
sleeve 32 in the manner explained above. The embodiment of the bottom 
insert shown in FIG. 3 is especially suitable for gun ammunition 
cartridges and provides for the use of relatively thin metal sheet 
materials without detracting from the strength of rim 36 required for 
ejection of the cartridge case after firing from a weapon. 
FIG. 4a shows a longitudinal sectional view of the cartridge case for an 
improved blank ammunition cartridge made essentially of a plastics 
material only. Preferably, the bottom insert not shown in FIG. 4a is made 
as explained in connection with FIG. 1 and 2 but advantages will be 
achieved even if a prior art all-metal insert is used. 
FIG. 4b shows a cross-sectional view of the cartridge case illustrated in 
FIG. 4a. Cartridge case 41 has an upper end piece 42 shaped as an 
imitation projectile and is made of plastics material throughout. The top 
of end piece 42 is furnished with a notch 43 at which the wall of the 
casing can rupture when a charge (not shown) contained in the chamber 45 
is detonated. Preferably, length K.sub.L of projectile-shaped end piece 43 
is at most 25% of the total length H.sub.L of the cartridge case, because 
this provides for savings in material and space and decreases the danger 
of an intentional or accidental weakening of case 41 in the transition or 
neck portion 47. Preferably, the inner wall surface of plastics cartridge 
case 41 is furnished with a number of ribs or webs 46 extending axially or 
helically in a continuous or interrupted manner over at least a part of 
the case wall. The volume of the internal charge-receiving space 45 of the 
case as well as the charge can be controlled in this manner, i.e. adaption 
to the intended charge volume and improved uniformity of charge 
distribution. In addition, ribs 46 may serve to prevent agglomeration of a 
charge consisting of particulate explosives. The outer wall of case 41 may 
be furnished with a number of troughs or grooves 18 for facilitating 
extraction of the case from the cartridge chamber of the weapon. 
Structuring of the cartridge case wall 41 as shown in FIG. 4b offers 
additional advantages in regard to manufacture of the cartridge case by 
injection moulding of thermoplastics as a uniform filling of the injection 
mould is facilitated by the internally and/or externally situated ribs and 
grooves, respectively. 
In the manufacture of cartridges for live ammunition of the type having a 
case made of plastics problems can arise due to inadequate or excessive 
strength of the connection between the case and the projectile. These 
problems can be resolved according to an embodiment of the present 
invention illustrated in FIG. 5a representing a longitudinal sectional 
view of the top portion of a projectile-bearing ammunition cartridge 
positioned in the cartridge chamber of a weapon. 
A bond control layer 55 is provided at the interface between projectile 51 
and neck 53 of cartridge case 57, preferably on the projectile surface. 
For metal projectiles, layer 55 is made of a bond improving agent, i.e. a 
composition capable of increasing adhesion between a metal surface 
(projectile) and a plastics surface (cartridge case) such as, for example, 
polymers of the type used for interbonding the metal and plastics 
constituents of metal-coated plastics laminates. Such polymers include 
polar groups and can be selected, for example, from the class of 
copolymers made of olefins and of unsaturated organic acids, unsaturated 
acid esters or salts of unsaturated organic acids (ionomers). 
When using projectiles made of plastics, on the other hand, the bond 
control layer will be of the type that decreases plastics/plastics 
adhesion or interwelding so that the plastics projectile will not be 
bonded too strongly to the plastics cartridge wall, e.g. when producing 
the plastics cartridge by injection molding with the projectile inserted 
into the mould. 
According to a preferred modification, cartridge case 57 is provided with 
shoulder elements 56 formed an an integral part of the plastics cartridge 
case so that projectile 51 can be pushed into neck 53 of a preformed case 
57 until the lower end of the projectile projects into the internal space 
52 of case 57 and bears against the shoulder elements 56. 
FIG. 5b further illustrates the arrangement of the shoulder elements in a 
cross-sectional view of the cartridge case of FIG. 5a. 
According to another preferred embodiment of the projectile-bearing type 
ammunition cartridge having a projectile made of plastics the lower 
portion 512 of projectile 51 that penetrates into neck 53 and case 57 has 
a larger cross-sectional diameter than the upper portion 511 of projectile 
51 that protrudes from the case, i.e. extends upward beyond edge 58 of 
neck 53. This embodiment assures that the ammunition cartridge can be 
inserted into the ammunition chamber of the weapon and easily removed 
therefrom even if not fired while, at the same time, providing for optimum 
projectile guidance in the barrel of the weapon upon firing. 
It is to be noted that the terms "plastics casing", "plastics projectile" 
and "made of plastics" are not intended as a restriction to such objects 
as consist entirely of a plastics material. In fact, the cartridge case or 
case wall of any embodiment of the cartridge according to this invention 
may include a reinforcing inlay or layer of fibres such as glass fibres or 
of sheets or foils including reinforcing metal layers of the type known 
for reinforcing plastics objects. Cartridge cases consisting essentially 
of plastics compositions that may, or may not include particulate or 
fibrous fillers are generally preferred, however, for reasons of economy. 
Cartridge cases consisting of thermoplastic polymer compositions can be 
shaped by blowmoulding techniques, or may possess a molecular orientation 
that provides for a more or less pronounced reinforcing effect. 
While the embodiments explained in connection with FIGS. 4a, 4b and 5a, 5b 
are preferably used with composite inserts of the type explained in 
connection with FIGS. 1-3, prior art all-metal inserts could be used if 
desired. 
The essential advantages of the novel composite cartridge bottom insert 
according to the invention can be realized in combination with any 
ammunition cartridge that has a plastics case, notably for use in blank or 
live rifle ammunition. In addition to reduced costs of materials and 
production, the novel insert provides for functional improvements believed 
to be due to the fact that the metal/plastics connection is situated 
within the bottom insert rather than between the bottom insert and the 
cartridge case. Furthermore, the novel composite bottom insert requires 
comparatively less metal per cartridge and can be manufactured at less 
costs per unit. 
Preferably, the novel bottom insert according to the invention is formed 
first by shapingly deforming, e.g. deep-drawing, of a metal sheet 
material, e.g. aluminum, aluminum alloy, steel, brass or the like, having 
a gauge substantially equal to that of the lower base portion of the metal 
bottom element, e.g. typically in the order of 1 mm (.+-. 0.3 mm) for 
rifle ammunition cartridges and, secondly, by anchoringly securing the 
metal element in the plastics sleeve element which may be preformed or, 
preferably, is formed of a suitable thermoplastics composition around the 
upper or anchoring portion of the metal element. Subsequently, a 
conventional detonator cap can be pressed into the cap-receiving and 
cap-holding chamber provided in the metal bottom element. Then, the 
completed assembly of cartridge bottom insert plus detonator cap is 
introduced into the lower end of the plastics cartridge case that may have 
a conventional structure or be designed in accordance with one of the 
preferred cartridge case embodiments disclosed herein. In general, a 
suitable charge will be provided within the case prior to closing its 
lower end with the cartridge bottom. Alternatively, the charge can be 
introduced via the top end of the cartridge case. 
According to a preferred specific embodiment of the inventive manufacturing 
method, the metal sheet for producing the metal bottom element is provided 
in the form of a disc that may, or may not, have a central aperture, and 
deforming such disc in a punch-dye or the like for shapingly deforming the 
metal disc and producing a generally tubular cylindrical protrusion which, 
in a subsequent shaping step is pressingly deformed so as to form a 
flanged or rimmed upper portion 23 as depicted in FIG. 2. Aperture 28 may 
be formed in connection with this second step unless the disc-shaped blank 
used had such an aperture to start with, or produced subsequently. 
Thus, it is apparent that the invention satisfies the objects, aims and 
advantages set forth above and provides for substantial improvements in 
connection with ammunition cartridges, notably for use in rifles. While 
the invention has been described in conjunction with specific embodiments, 
it is evident that many alternatives, modifications and variations will be 
apparent to those skilled in the art in the light of the foregoing 
description. Accordingly, it is intended to embrace all such alternatives, 
modifications and variations that fall within the spirit and broad scope 
of the appended claims.