U.S. patent number 3,745,924 [Application Number 05/023,861] was granted by the patent office on 1973-07-17 for plastic cartridge case.
This patent grant is currently assigned to Remington Arms Company, Inc.. Invention is credited to John J. Scanlon.
United States Patent |
3,745,924 |
Scanlon |
July 17, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
PLASTIC CARTRIDGE CASE
Abstract
A plastic cartridge whose ballistics are equivalent to existing
metallic cartridges and which can be fired in existing firearms. A
non-expanding metal head is securely attached to the breech end of
the plastic casing by compressively squeezing the rear end of the
plastic casing between a metal head and a second metallic member,
either an annular support member plus a primer or by the primer
itself. The plastic casing is preferably formed by drawing at least
the front end of the casing and then necking down the mouth
portion. The preferable plastic materials for cartridge casings
include polycarbonates, polysulfones, and blends of plastics, e. g.
a blend of polyethylene and polycarbonate, a blend of polyethylene
and polysulfones, and alloys of polysulfones and
polycarbonates.
Inventors: |
Scanlon; John J. (Monroe,
CT) |
Assignee: |
Remington Arms Company, Inc.
(Bridgeport, CT)
|
Family
ID: |
21817633 |
Appl.
No.: |
05/023,861 |
Filed: |
March 30, 1970 |
Current U.S.
Class: |
102/467 |
Current CPC
Class: |
F42B
5/36 (20130101); F42B 5/307 (20130101) |
Current International
Class: |
F42B
5/00 (20060101); F42B 5/36 (20060101); F42B
5/307 (20060101); F42b 005/30 () |
Field of
Search: |
;102/38,43,43P,43F,42 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
832,561 |
|
Apr 1960 |
|
GB |
|
919,583 |
|
Sep 1945 |
|
FR |
|
Primary Examiner: Stahl; Robert F.
Claims
What is claimed is:
1. A cartridge comprising a one-piece casing made of thermoplastic
material which is substantially non-combustible under normal firing
conditions, said plastic casing having a tubular body portion with
a rear breech end and a forward mouth end, said tubular body
portion being substantially closed off adjacent its breech end by
an integral transverse wall portion and open-ended at its forward
mouth end, a relatively thin-walled annular flange projecting
rearwardly from said transverse wall portion and extending to the
breech end of the cartridge, said annular flange having a diameter
less than the diameter of said tubular body portion, a head means
made of rigid metallic material in close-fitting engagement with
the outer periphery of said annular flange, a metallic annular
support positioned on the opposite side of said flange from said
head means and co-operating therewith to place said plastic flange
in compression, primer means frictionally located within said
annular metallic support so as to exert additional compressive
pressure against said flange, and a flash hole opening in said
transverse wall portion which permits access from said primer means
to the interior of the tubular body portion, said rigid metallic
head means having sufficient yield strength so as to prevent
permanent expansion of the head upon firing of the cartridge.
2. A cartridge as recited in claim 1 in which said metal head is
made of hardened steel having a hardness ranging from about RC45 to
about RC50.
3. A cartridge as recited in claim 2 wherein at least the forward
mouth end of the tubular body portion has been cold worked in order
to decrease the thickness of the tubular body wall and increase the
strength characteristics of the forward mouth end, said forward
mouth end being necked down to a smaller diameter in order to
accommodate a single projectile.
4. A cartridge having a drawn plastic cartridge casing, said casing
comprising a tubular body portion having a front mouth end and a
rear breech end, said front mouth end being necked down to form a
smaller-diameter mouth portion in which a single projectile means
is positioned, a transverse wall portion integral with said tubular
body portion and located adjacent to but spaced from the breech end
of the casing, an annular ring means integral with and projecting
rearwardly from said transverse wall portion, said ring means being
held in compression by an outer rigid metallic head member and a
separate inner flexible metallic member.
5. A cartridge as recited in claim 4 in which said necked-down
mouth portion has been cold worked more than any other portion of
the plastic cartridge casing and thus has improved strength
properties over the remaining portions of the casing.
6. A cartridge as recited in claim 5 wherein said outer metallic
head is made of material which is substantially unyielding under
the intended pressure and said inner metallic member is made of
material which is rigid enough to co-operate with the rigid head to
put the annular plastic ring in compression but still flexible
enough to permit the inner member to expand outwardly against the
annular plastic ring upon firing to act as a gas seal
therewith.
7. A cartridge having a drawn plastic casing, said casing having a
tubular body portion and a front mouth portion which has been
elongated in an axial direction as well as expanded outwardly so as
to decrease the wall thickness of the body at the mouth end
thereof, and to provide additional strength thereto, said mouth
portion being necked down to provide an opening which is of lesser
diameter than said tubular body portion, a single projectile
secured in said mouth opening, said plastic casing being made of a
thermoplastic material selected from the group of plastics and
blends of plastics having high impact strength, dimensional
stability, high flexural modulus, and high deflection temperature,
consisting of polycarbonates, polysulfone, blends of minor portions
of polyethylene with polycarbonates, blends of minor portions of
polyethylene with polysulfone, and alloys of polysulfones and
polycarbonates
Description
This invention relates to cartridges for firearms, particularly to
cartridges having plastic body casings with metal heads attached to
the breech ends of the cartridges, and the method of attaching the
metal heads to the plastic body casings. Another aspect of this
application relates to the drawing of certain plastics and blends
and an alloy of plastics which heretofore had not been cold worked
for ammunition purposes.
Although shotgun shells made of biaxially oriented plastic
materials have been on themarket for about 10 years, e. g. as shown
in U.S. Pat. No. 3,103,170, issued to Covington et al., on Sept.
10, 1963, there has been no real use of thermoplastic materials,
either injection molded or cold worked, in high-powered rifle or
center fire ammunition. Probably the main reason for this is that
explosive pressures generated in center fire ammunition are much
greater than in shotgun shells, e. g. about 50,000 psi as compared
to 10-11,000 psi for shotgun shells. The operating requirements
have just been too much for the various plastic center fire shells
developed up to now except for some miscellaneous training or
practice cartridges where the pressures are even less than in
shotgun shells.
If the operating requirements for ammunition for single-shot
high-powered rifles are demanding, the demands for automatic
weapons, e. g. the M-16 rifle or machine guns, are even more so
because of the high rate of loading, firing, extraction, and
ejection which require mechanically strong casings and thermally
stable and resistant casing material because of the heat generated
in the guns by the rapid, automatic firing.
The search for suitable cartridges to replace the conventional
brass or other metal case cartridges has gone on for a long time.
In recent years this search has been accelerated because of the
scarcity and high cost of brass. Primary emphasis in recent years
has been focused on: (1) caseless ammunition in which the
projectile does not have any cartridge casing and where the
propellant is either located within the projectile or attached to
it by some attaching or adhesive means; (2) combustible cartridge
casings which are designed to be completely combustible while in
the gun, and (3) expendable cartridge casings which are not
combustible but which are designed to be completely expelled from
the gun along with the projectile.
The present invention relates to another approach which includes
the advantages of: (1) having less weight than conventional
ammunition; (2) being less expensive to manufacture; (3) avoids use
of critical materials such as brass or aluminum; (4) utilizing an
extractable cartridge casing; (5) being interchangeable with
conventional ammunition in existing guns; (6) being strong and heat
resistant enough to be used in automatic weapons, and (7) requires
less propellant powder for equivalent ballistics than conventional
ammunition probably because of the thermal insulation properties of
the plastic cartridge.
The major object of this invention is to provide a plastic-bodied
cartridge which has sufficient strength to withstand the handling,
storing, and firing requirements of modern firearms.
Another object of the invention is to provide a unique plastic
casing to metal head attachment and the method of attaching
thereof.
Another object of the invention is to provide a plastic-bodied
cartridge which is suitable for high-powered center fire use.
Another object of the invention is to provide a plastic-bodied
cartridge which will provide ballistics which are equivalent to
conventional ammunition and which can be fired in existing firearms
without modifying the forearm.
Another object of the invention is to provide a drawn-plastic
casing in which the mouth end is necked down and cold worked to
provide additional strength.
Another object of the invention is to provide a drawn-plastic
casing which utilizes plastics, or blends or alloys of plastics,
which have not been cold worked previously for ammunition
purposes.
Another object of the invention is to provide plastic cartridges
which are suitable for the demanding requirements of automatic
weapons.
Other objects will be apparent from the specification and drawings
in which:
FIG. 1 is a sectional side view of a loaded cartridge which
incorporates the present invention.
FIG. 2 is a sectional side view of the molded plastic slug prior to
being drawn.
FIG. 3 is a sectional side view of the plastic casing after
drawing.
FIG. 4 is a sectional side view of the drawn plastic casing of FIG.
3 with a battery-cup type metallic member positioned in the primer
cavity.
FIG. 5 is a sectional side view of the drawn plastic casing of FIG.
4 with a metallic head member positioned thereon.
FIG. 6 is a sectional side view of the drawn plastic casing of FIG.
5 with the front end necked down to form a smaller diameter mouth
portion.
FIG. 7 is a sectional side view of the drawn plastic casing of FIG.
6 having a primer positioned in place.
FIG. 8 is a side elevation of the equipment used to draw the
plastic slug.
FIG. 9 is a side elevation of the equipment used to neck down the
mouth end of the cartridge casing.
Referring now to the drawings, FIG. 1 illustrates a loaded round of
ammunition 10 in which the elongated body casing 12 is made of a
suitable plastic material, e. g. polycarbonate. Other thermoplastic
materials are also suitable and will be discussed later.
Plastic casing 12 has a main body portion 14 which is necked down
at its front end 16 to form a mouth portion in which projectile 18
is secured by a force fit or any other conventional manner.
A transverse wall 20 closes off the body casing 12 adjacent to the
breech end 22 thereof and includes a flash hole opening 24 therein.
Integrally formed with the transverse wall 20 and projecting
rearwardly to the breech end or breech face of the cartridge is a
realtively thin-walled, annular skirt or flange member 26. The
inner periphery 26A of the skirt 26 and the rear wall surface 20A
of the transverse wall 20 (see FIG. 4) define a primer cavity 28 in
which a battery-type metal cup or annular support member 30 is
positioned in force-fitting relationship. Co-operating with cup 30
in placing the annular skirt 26 in compression is a metal head
member 32 which engages the outer periphery 26B of skirt 26.
Positioned within cup 30 in force-fitting relationship is a
metallic primer 34 which assists in putting the plastic annular
skirt 26 in compression. Positioned within the main body portion is
a propellant means 36. It should be appreciated that skirt 26
should be thin enough so that the skirt can be put in compression
by the action of the metal head 32 and the cup 30.
Although FIG. 1 shows the metal head-plastic casing attachment as
it applies to a center-fire type cartridge, in this case the 5.56
mm, it should be noted that the invention could also be used with
shotgun shells or pistol cartridges where the outer periphery of
the metal head could either be flush with the outer periphery of
the body 12 (as shown) or it could extend outwardly of the body
cavity.
In the embodiment shown, the metal head 32 is made of hardened
steel (RC 45-50) which has a yield strength of about 110,000 psi in
order to prevent head expansion into unsupported areas under firing
pressures of about 50,000 psi. Obviously, for other firing
pressures other unyielding or non-expanding head members may be
suitable.
The battery type cup or annular support member 30 is also made of
metal, preferably brass, copper, steel, or any other suitable metal
which is rigid enough to co-operate with the steel head 32 to put
the plastic annular skirt under compression but which nevertheless
will flex under firing pressure to expand outwardly against the
skirt to act as a gas seal. The primer 34 can be made of any
metallic materials of which conventional primers are made, e. g.
brass, steel, copper, etc.
Although FIG. 1 shows the use of a battery-cup type of support and
a primer, it has been found that for many uses a suitable
casing-head attachment can be effected by omitting the battery cup
and having the primer inserted directly against the inside
periphery of the skirt to co-operate with the rigid head to put the
skirt under compression. However, it has been found that for severe
conditions, such as automatic fire, the addition of the battery cup
is useful in preventing primer blow-out and in reinforcing the
head-casing attachment.
FIGS. 2 through 9 illustrate another aspect of the invention, i.e.
the drawing of the molded casing slug 12A (shown in FIG. 2) to the
elongated and drawn casing 12B (shown in FIG. 3) and finally necked
down to the finished cartridge casing 12 (shown in FIG. 6).
Although the dimensions are not shown on the drawings, the breech
end of the finished casing is substantially the same as the
original molded slug whereas the plastic slug is elongated in an
axial direction as well as expanded outwardly so as to decrease the
wall thickness of the body at the mouth end. The cold working of
the plastic slug improves the tensile strength of the finished
casing as can be seen below. In addition to polycarbonate casings,
other plastics were used to make body casings, including various
blends and alloys of plastics.
TABLE I
TENSILE TESTS ON DRAWN PLASTIC ALLOYS
Before After ALLOY Drawing Drawing (Loading Rate 2"/Min.) 100%
Polyethylene 4,100psi 5,500psi 98.75% Polyethylene 1.25%
Polycarbonate.sup.1 4,400psi 5,700psi 97.5% Polyethylene 2.5%
Polycarbonate 3,900psi 6,200psi 95% Polyethylene 5% Polycarbonate
4,300psi 5,800psi 62% Polyethylene 38% Polycarbonate 5,500psi
9,200psi 33% Polyethylene 67% Polycarbonate 6,280psi 7,800psi 16%
Polyethylene 84% Polycarbonate 7,310psi 9,700psi 8% Polyethylene
92% Polycarbonate 7,139psi 9,100psi 4% Polyethylene 96%
Polycarbonate 9,380psi 16,100psi* 1% Polyethylene 99% Polycarbonate
10,600psi 17,600psi 90% Polyethylene 10% Nylon 3,900psi 4,400psi
100% Nylon 9,200psi 21,900psi* 100% Arylon 7,500psi 11,600psi 10%
Polysulfone 90% Polycarbonate 11,900psi 20,200psi* 25% Polysulfone
75% Polycarbonate 11,900psi 21,100psi* 50% Polysulfone 50%
Polycarbonate 12,500psi 20,200psi* 100% Polycarbonate.sup.2
10,900psi 19,950psi* 100% Polysulfone 10,950psi 19,650psi* *Cases
were fired as retrofit cases.
The polyethylene mentioned above is a high-density polyolefin of
the type sold by E. I. du Pont de Nemours and Company as ALATHON
7320. The polycarbonate.sup.1 is a high molecular plastic sold by
the General Electric Company as LEXAN 101-111. The
polycarbonate.sup.2 is a low molecular weight plastic better suited
for thin wall use and is sold by the General Electric Company as
LEXAN 141R. ARYLON is a polyaryl ether sold by Uniroyal as T-3198
and was too brittle for this use. The polysulfone used is sold by
the Union Carbide Company as P 1700 and has excellent temperature
resistance.
The polyethylene is added in small amounts to make a blend with
polycarbonate and polysulfone (although not listed above) in order
to make the plastic blend compatible with solvents and the
environment, e. g. to relieve stress cracking. When too much
polyethylene is added, the blend becomes too brittle.
The addition of polysulfone to polycarbonate results in improved
temperature resistance. The two plastics mix together to form an
alloy and result in a homogeneous mass as opposed to the blend of
polyethylene and polycarbonate or polyethylene and polysulfone
where the plastics do not mix or form into a homogeneous mass.
Thus, the polysulfone and polycarbonate can be mixed in about equal
proportions without causing brittleness.
FIG. 8 shows a plastic slug 12A positioned on a vertically movable
punch 36 before the punch and slug are moved through the die means
38 so as to elongate and expand at least the front end of the
casing. This particular method of drawing is not new and has been
used for years in drawing brass cases so it does not appear
necessary to go into detail on the drawing process.
FIG. 9 shows a die means 40 in position around casing 12 just after
necking down the mouth end of the casing. Again, this particular
operation is not novel and thus it does not appear necessary to
enlarge the specification with extraneous matter which does not add
to the understanding of the invention being claimed. This type of
equipment is clearly shown, for example, in drawing aluminum cases
in the U.S. Pat. No. 3,498,221, issued to R. W. Hilton et al., on
Mar. 3, 1970.
Although shotgun shells made of injection molded polycarbonates are
presently on the market, it is not known that polycarbonate or
polycarbonate blended or alloyed with other plastics have been cold
worked before to form cartridge cases. Although polyethylene has
been drawn, impact extruded, etc., to form strengthened or oriented
plastic casings, the amount of recovery of polyethylene in necking
down the mouth end of the present invention prevents or seriously
curtails its use for center fire ammunition because the mouth will
not fit tightly against the projectile. Where the mouth is open or
not necked down, such as in shotshells or pistol cartridges,
polyethylene is satisfactory. Moreover, the novel casing-to-head
attachment of the present invention is compatible with polyethylene
casings. The real advantages of polycarbonates and polysulfones or
alloys of either of these with each other or blended with
polyethylene are in the improved yield strengths obtainable, their
high resistance to heat, and their ability to retain dimensions
after being cold worked. By using polycarbonates with
polyethylenes, we improve the long storage characteristics of
polycarbonate. Casings have been made, as shown in the above table,
having dimensions which permitted successful firing of as much as a
14-round burst in an M-16 rifle which was not modified in any
manner to accept, fire, extract or eject plastic cartridges.
Heretofore, injection molded casings have been made although at a
sacrifice of ballistics or by modifying the guns.
The physical characteristics of the preferred plastics which
contribute to their acceptable performance over known plastics such
as polyethylene. These characteristics, which are measurable, are
higher tensile strength, higher heat deflection temperature, and
higher flexural modulus.
Although high density polyethylene can be cold worked to very high
tensile strengths, the amount of cold working in the present
instance does not result in sufficient tensile strength in
polyethylene to be suitable for the purpose intended. Also, as
explained above, the amount of recovery of polyethylene in necking
down the mouth of the casing rules out the use of polyethylene.
These properties are measurable and known and are listed for
example in the Modern Plastics Encyclopedia for 1968-69, Volume 45:
No. 14A, October 1968, published by McGraw-Hill Inc. From this
publication, we note the following values listed: ##SPC1##
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