CA1053074A - Base wad for shotshells - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A base wad for shotshells integrally constructed of non-linear polyethylene and a mineral from the class consisting of asbestos, barium carbonate, chalk, and talc in approximately equal portions by weight; said base wad being dimensionally stable, having requisite flowability for snug locking with the shotshell head and the rim thereof; and being of appropriate elasticity to provide excellent sealing of the gases of explo-sion while being readily restored to normal condition for ease or ejection of the shotshell from the fun firing chamber.

Description

_ ~ ieretofore, considerable efforts have been e~pended in developing and improving base wads for shotshells. The primary problem has been to incorporate wi~hin a single base wad all of the desired attributes thereoE. A base wad must be adapted for interlock with the s~lotshell heacl, as by flowing into the rim portion th0reof, Eor gas sealing purposes; as well as to provicle a snug joint witll the tube wall so that the Eorce of the explosion, upon -Eiring, will not be ineffectively dissipated. Additionally, it is of extreme criticality that a base wad be resistant to permanent deformation so that swelling, as it were, of the shotshell head is prevented for assuring ready e]ectability or removal of the fired shotshell from the gun firing chamber. Base wads must necessarily embody appropriate elasticity so as to return to normal condition from any momentary distention or expansion upon firing. Furthermore, base wads must be dimensionally stable over long periods of time and without regard to the conditions of storage so that moisture ;~
gain or loss with attendant volumetric change does not occur to assure of optimum and consistent ballistic characteristics.
With the ever increasing demand for shotshells which are adapted for reloading by the individual shooter further requisites for base wads have become more evident, such as durability, so that the respective shotshell may be reloaded numerous times before there is any failure in the base wad.
Also, economy is a serious factor.
The attempts to date to develop a base wad which ;
contains the spectrum of desired properties have not been successful. In each instance at least one important deficiency has been present. Among such efforts has been the development of base wads of two-part construction embodying interlocking components; and the provision of base wad overlays, all of which , ~5i3~7~ :

prove most costly in production and of dubious gas sealing capabilities. Integrally formed wads have been primarily formecl of convolute wound paper but the same frequently split upon firing which, understandably, brings about a 5welling of the head for obstructing shell ejections. Further- ;
more, wads of cellulosic materials are subject to dimensional alteration by the absorption and loss of moisture through changes in an~ient conditions. Base wads formed of plastic materials such as linear polyethylene have proved to be altogether too costly as well as extremely difficult in forming.
Another effort has been to mold a base wad from linear polyethylene and such is exemplified in the Comerford U.S.
Patent No. 3,~69,311. Linear polyethylene is of high density and is relatively harcl, being incapa~le of flowing sufficiently during the heading operation to properly lock into the head.
Such linear polyethylene is too hard to retain a dish-shaped surface adjacent the propellant to provide an effective seal.
If the heading pressure is increased to overcome this deficiency in flowability, the tube of the shell will be cut before arriving at a pressure high enough to reform such plastic.
In view of the inherent resistance to reforming in the heading operation with resultant insufficient locking of such wads in the shell rim, the loss of the same from ~he shell after firing has been customarily encountered with such base wad remaining in the gun barrel and providing a condition where in the barrel may burst upon firing of the next shell. Accord-inglyr wads formed from linear polyethylene thus provide a very frightful hazard and because of their lack of capacity to reorm, have not proved popular with the individual reloader.
~nother prior art effort at developing a base wacl is of the character shown in the Dau~enspeck et al Patent :

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~o . 3 ~ 270 r 671 wherein the base wad is comprised of 30-60%
of asbestos fibers and 70-40~ of wood fibers, held together I with a microcrystalline wax binder in a quantity ecluivalent to about 8~ by weigllt of the asbestos wood fiber mixture.
~7ads of this particular type are not impervious to moisture ancl, hence, may absorb moisture from the powder or could, conversely, transfer absorbed moisture to the powder which in either case woul~ have a severe and marked effect upon the balli~tics. Furthermore, upon firing the temperatures developed are sufficient to effect some melting of the wax binder so that the outer surface of such base wads tends to Eragment and become loose and thereby makes it extremely difficult, if not impossible, to reload the shell. An ; individual atteI~pting to reload a base wad of the type now -~
being discussed must use a hot spinnincJ iron to repress the base wad before reloading to overcome the surface fragmentation.
Also, it is evident -that due to the moisture absorptive capacity of the base wads, the same are extremely sensitive to ambient conditions. It is evident that asbestos wood fiber , base wads are not amenable to production by extrusion or injection molding but can only be formed by mechanical inter-mixing and subsequent compression.
Therefore, it is an object of the present invention to provide a base wad which may be most economically produced;
which is raadily formable so as to assure positive locking with the shotshell head; which is dimensionally stable, being ~; resistant to moisture absorption or loss; which is highly . . .
durable; and which is resistant to failure so as to conduce to extensive reloadability of the associatPd shotshell.

It is another object of the present invention to ~ ; provide a shotshell base wad which is constructed of a readily ~ `
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flowable, normally soft thermoplastic and mineral filler whereby the base wad is endowed with the elasticity and form-ability of the plastic -toyether with the stability and strength contributed by the mineral.
It is a further object of the present invention to providei a base wad of the character stated which is amenable to high volume, rapid economic produc-tion by a variety of readily practiced methods.
It is a still further object of the present invention -~o provide a method for producing one-piece base wads of the present invention.
It is another object of the present invention to provide a base wad which is fireproo~ and thus being adapted for safe storage as well as conducing to non-hazardous reloading.
These objects are attained by the invention which contemplates a shotshell base or under-powder wad having a unitary, integrally formed body consisting essentially of a normally soft, relatively low molecular weight, non-linear, non-copolymerized thermoplastic and a naturally occurring mineral. The body has uniform consistency throughout its extent.

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In the drawings wihich illustrate embodiments of the invention...
The FIGURE is a side view of a shotshell, having a portion of the side all broken away, and being in partial section, incorporatiny a base wad produced in accordance with and embodyincJ the present invention.
In essence, the present invention contemplates the construction of a base wad for shot gun shells, which by weight is constructed in substantially equal parts of non-linear polyethylene and a mineral, such as asbestos, barium carbona-te, chalk, and talc; said latter sometimes being referred to herein as a filler. The non-linear polyethylene is normally relatively soft and is relatively low molecularly, ~nd would not alone be adeguate for base wad formation since -the same would ~e entirely too soft for the requirements of a base wad. However, the same does inherently have a ready deform-abili~y as well as substantial elastici~y. By the amalgamation with an appropriate relative guanti~y-of the particular filler, a resultant composition is brought about which possesses the hardlless and elasticity necessary for an eEfective base wad.
By such unique combination the inherent characteristics of the non-linear polyethylene are adapted for base wad usage which was not heretofore conceived. 1~ has been found that optimum base wad properties are developed by a composition which is approximately 50 percent by weight of the said non-linear polyethylene and approxima-tely 50 percent by weight of the par-ticular filler. -~
Base wads constructed in accordance with the present invention have proved extremely formable so that by the customary heading operation the same will flow adequate~y undex ; compression to bring about an intimate and positive interlock :::
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with the 'nead and especially within tAe rim volume. ~hus, normal pressures may be used in such operation with full assurance that the intendecl interlock will be brouqht about;
thereby assuriny against any clanger -to the ~shell tube durincJ
reformincJ. Ey such formability excellent gas sealing is accorded the relatecl shotshell as leakage is eliminated within the rim area, and furth~rmore, undesired relative dislodyment of the base wad is inhibitecl since the same is prevented from moving relatively upwardlv within the shell upon iring. -~
Furthermore, such properties permit of the development of the appropriate dish shaped surface underlying the propellant charge to provide an effective seal.
The particular filler of the present invention uniquely modifies the inherent elasticity of the normally soft non-linear polyethylene so as to accord the resultant base wad wi-th the desired resiliency so that the base wad will immediately return to normal dimensions subsequent to the expected initial -expansion occurring upon explosion. By virtue of this capacity base wads so constructed will eliminate the danger of causing the shotshell to become jammed within the firing chamber or to contribute to any difficulty of extraction of the same.
Manifestly, by such elasticity the base wads will maintain ` an especially tight joint with the cartridge tube immediately upon firiny and thereby further conduce to prevention o~ gas leakage so that substantially the full orce of explosion will be used Eor the propulsion of the waddin~ and the shot.
Furthermore, the particular filler of the present invention lends substantial strength to the base wad so that the same will have good contrast during percussion of the primer as well as resist deformation o the forces o . . .
~ ~ explosion.

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~.~S3~74 The non-linear polyethylene used by itself, that is, without modification by one of the present fillers/ would be entirely too soEt so that firing pressure would cause a swelling of the head of the shell and inhibit extracting of the fired shell from the gun.
In view of the foregoing it is indeed apparent that ~ase wads so constructed are particularly suitable for shot gun cartridge reloading as effected by the average inclividual shooter; it being recognized that non-linear 10 polyethylene and the present Eillers are relatively cheap materials of construction and the integration of the same into t a base wad may be achieved by practice of a most economically performed method.
rrhe Figure of the drawing merely illustrates a shot-shell designated generally A having the customary tubular casing 1, head 2, with a base wad 3 formed in accordance with the present invention and embodying the customary bore 4 for receiving a primer 5. A propellant charge 6 is provided upon base wad 3 with there being an obturating wad 7 surmountiny 20 said charge 6 and with the customary filler or separator ,- .:
wads 8,9 disposed thereabove. A so-called missile charye 10 is -~
disposed above wad 9 and the upper end portion of casing 1 may be olded inwardly, crimped, or otherwise closed for completiny the assembly of shotshell A. Said drawing is provided merely for purposes of reference for clarifying the relationship of base wad 3 with the other components of shotshell A, and particularly for depicting the snug lock within the rim of head 2 indicated at r.
Extensive testing has demonstrated that the present base 30 wads are dimensionally stable, as the unique composition of the aMe is not measurably absorptive of moisture, thus being ~-:

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proof against moisture transfer in either direction with -- respect to the propellant charge so as to assure o:E consistent and reliable ballistics without regard to the number of Eirings.
~ccordingly, no processincJ steps o any type are required ` .
for reloadiny.
Base wacls of this invention may be prepared by a method which is es-pecially suited for conmercial procluction;
the same encompassing the utilization of pellets or scrap of non linear polyethylene which has been pre:Eerably ground :Eor~
10 passing an 8 mesh screen and with scrap asbes tos fiber.
Said raw materials are charged in substantially equal amounts to a rnechanical mixer. After the mixing operati~n the resultant mass is then inserted in an extruder for extrusion in rod forrn. ~lhe extruded rod is then subjected to a chopping ~;
operation with the resultant particles being then submitted to a further extruding oparation for assuring ~he complete intermixing of the asbestos. The second extruding operation -provides a relatively thick-walled tube. The latter may be cut . in desired increments and with the severed portions being then `
20 subjected to conventional forming operations as by suitable dies to complete the base wad construction and the latter may then be sub; ected to the customary heading opera tion as by sub j ec tion to an internal punch under subs-tantial pres sure for causing material of the base wad to flow into the rim area -.
of the head. ~.
However, it is to be understood that instead o:E .:
asbestos fiber, barium carbonate, chalk or talc may be used . . . ~ .
without any altera-tion in the method.

It will be observed that the present base wad 30 has but two components, namely the non-linear polyethylene and the filler from the group comprised of asbestos, talc, i .
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chalk and barium carbonate; there being no need for a binder or adhesive, such as wax or the likeO Formed in he manner herein taught, base wads of the present invention have maxim~n pllysical integrity so that -fragmenting, splitting, rupturing, deforminy do not occur on shell firillg. The above Eillers une.xpectedly cooperate with the non-linear polyethylene to ~ive the resultant base wad such physical inteyrity as well as the reauisite flowability which could not be obtained from non-linear polyethylene alone.
Accordingly, in view of the foregoing, it will be seen that the unique combination of low density, normally soft, relatively low molecular, non-linear polyethylene and a mineral Erom the class consisting of asbestos, barium carbonate, chalk and talc br.ings about a resultant base wad with requisite hardness, yet improved primer sensitivity; excellent .. -extraction; superby interlock with the shell head being .
substantially non-moisture absorptive and also excellent physical integrity, there being no swelling aEter firing.

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Claims (12)

The embodiments of the invention in which an exclusive property ox privilege is claimed are defined as follows:

1. A shotshell base or under powder wad having a unitary, integrally formed body consisting essentially of a normally soft, relatively low molecular weight, non-linear, non-copolymerized thermoplastic and a naturally occurring mineral, said body having uniform consistency throughout its extent.

2. A shotshell base wad as defined in Claim 1 and further characterized by said thermoplastic and said mineral each constituting approximately 50 percent by weight of the base wad.

3. A shotshell base wad as defined in Claim 2 and further characterized by said thermoplastic being poly-ethylene.

4. A shotshell base wad as defined in Claim 3 and further characterized by said mineral being from the glass consisting of asbestos, barium carbonate, chalk, and talc.

5. The combination with a shotshell having a tubular easing and a head, said head having a rim of a base or under powder wad disposed in said easing and interlocked with said shotshell head and the rim thereof, said base wad comprising a unitary body integrally formed and consisting essentially of a normally soft, relatively low molecular weight, low density, non-linear, non-co-polymerized, substantially water insoluble polyethylene and a naturally occurring mineral, said body being of uniform consistency throughout its extent.

6. The combination as defined in Claim 5 and further characterized by said mineral being from the class consisting of asbestos, barium carbonate, chalk and talc.

7. The combination as defined in Claim 6 and further characterized by said polyethylene and said mineral each constituting approximately 50 percent by weight of the base wad body.

8. A method for producing a shotshell base wad comprising providing non-linear polyethylene in discrete particulate form, providing a substantially equal amount by weight of a mineral from the class consisting of asbestos, barium carbonate, chalk and talc in discrete particulate form, intermixing said non-linear polyethylene and said mineral, then extruding the intermixtures in rod form, then severing the formed rod into individual sections, then subjecting the severed sections to an extruder for producing a relatively thick-walled tube, then severing the tube into predetermined lengths and then subjecting the severed lengths to base wad forming action.

9. A shotshell base wad having an integrally formed body consisting essentially of a normally soft, relatively low molecular weight, low density, non-linear, non-copolymerized polyethylene and a mineral from the class consisting of asbestos, barium carbonate, chalk and talc.

10. A shotshell base wad as defined in Claim 9 and further characterized by said polyethylene and said mineral each constituting approximately 50 percent by weight of the base wad.

11. In combination with a shotshell having a tubular casing and a head, said head having a rim, a base wad disposed in said casing and interlocked with said head rim, said base wad consisting of a body integrally formed from normally soft, relatively low molecular weight non-linear, non-copolymerized polyethylene and asbestos, said non-linear polyethylene and said asbestos each constituting approximately 50% by weight of the base wad body.

12. A shotshell base wad as defined in Claim 1, Claim 3 or Claim 5 and further characterized by said mineral being asbestos.