U.S. patent application number 14/075188 was filed with the patent office on 2014-10-16 for magnesium firearm forearm and method of manufacture.
The applicant listed for this patent is MAG Tactical Systems, LLC. Invention is credited to William Carr King, JR..
Application Number | 20140305019 14/075188 |
Document ID | / |
Family ID | 51685782 |
Filed Date | 2014-10-16 |
United States Patent
Application |
20140305019 |
Kind Code |
A1 |
King, JR.; William Carr |
October 16, 2014 |
MAGNESIUM FIREARM FOREARM AND METHOD OF MANUFACTURE
Abstract
A forearm for a firearm that includes a magnesium alloy body.
The forearm can be adapted for use in a modular rifle having both
an upper receiver securable to a barrel and a lower receiver
housing a trigger assembly. The magnesium body may also be nickel
plated and have a ceramic coating on the nickel plating. Also
disclosed are methods of manufacturing a forearm having a magnesium
alloy body. The magnesium alloy body may be formed by extrusion or
by thixotropic molding. In some embodiments, the magnesium forearm
includes an outer sleeve formed out of a magnesium alloy and an
inner sleeve formed out of a different material.
Inventors: |
King, JR.; William Carr;
(Newburgh, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAG Tactical Systems, LLC |
Bargersville |
IN |
US |
|
|
Family ID: |
51685782 |
Appl. No.: |
14/075188 |
Filed: |
November 8, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61863195 |
Aug 7, 2013 |
|
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|
61846674 |
Jul 16, 2013 |
|
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61735254 |
Dec 10, 2012 |
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Current U.S.
Class: |
42/71.01 ;
29/527.4; 72/254; 72/256; 72/362 |
Current CPC
Class: |
F41C 23/16 20130101;
F41C 23/18 20130101; Y10T 29/49986 20150115 |
Class at
Publication: |
42/71.01 ;
72/362; 29/527.4; 72/256; 72/254 |
International
Class: |
F41C 23/18 20060101
F41C023/18; F41C 23/16 20060101 F41C023/16 |
Claims
1. A firearm comprising: a receiver operably coupled with a barrel;
and a forearm securable to the firearm and comprising a magnesium
alloy body.
2. The firearm of claim 1 wherein the firearm is a modular rifle
and wherein the receiver comprises an upper receiver and a lower
receiver; the forearm and the barrel being mountable on the upper
receiver and the lower receiver housing a trigger assembly.
3. The firearm of claim 1 wherein the magnesium alloy body has a
layer of nickel plating applied thereto and a ceramic coating is
applied over the layer of nickel plating.
4. The firearm of claim 1 wherein the magnesium alloy body forms an
outer sleeve and the forearm further comprises an inner sleeve
formed out of a non-magnesium material, the outer sleeve being
disposed about and engaged with the inner sleeve.
5. The firearm of claim 4 wherein the inner sleeve comprises a
steel material.
6. The firearm of claim 4 wherein the firearm is a modular rifle
wherein the receiver comprises an upper receiver and a lower
receiver; the lower receiver housing a trigger assembly and the
forearm and the barrel are mountable on the upper receiver.
7. The firearm of claim 1 wherein the forearm is defined by a pair
of separable parts which substantially encircle the barrel when
secured together.
8. The firearm of claim 1 wherein the forearm is a unitary forearm
which substantially encircles the barrel.
9. A method of manufacturing a firearm forearm comprising: forming
a magnesium alloy body; and processing the magnesium alloy body to
form at least a portion of the forearm.
10. The method of claim 9 further comprising the steps of plating
the magnesium alloy body to form a layer of nickel plating on the
magnesium alloy body and applying a ceramic coating on the layer of
nickel plating.
11. The method of claim 9 wherein the step of forming a magnesium
alloy body comprises thixotropically molding the magnesium alloy
body.
12. The method of claim 11 wherein the magnesium alloy body has a
surface roughness, R.sub.a, that is between approximately 35
microinches and approximately 60 microinches after molding and
without any post-molding processing to smooth the surface.
13. The method of claim 9 wherein the step of forming a magnesium
alloy body comprises extruding the magnesium alloy body.
14. The method of claim 13 wherein the magnesium alloy body forms a
forearm that substantially encircles the barrel.
15. The method of claim 14 further comprising cutting the magnesium
alloy body lengthwise to form two separable parts of the
forearm.
16. The method of claim 15 wherein the two separable parts have the
same configuration.
17. The method of claim 13 wherein the forearm includes an inner
sleeve and an outer sleeve disposed about the inner sleeve and
wherein the magnesium alloy body forms the outer sleeve of the
forearm and the method further comprises providing a non-magnesium
insert to form the inner sleeve.
18. The method of claim 9 wherein the forearm includes an inner
sleeve and an outer sleeve disposed about the inner sleeve and
wherein the magnesium alloy body forms the outer sleeve of the
forearm and the method further comprises providing a non-magnesium
insert to form the inner sleeve.
19. The method of claim 9 wherein the magnesium alloy body is
formed out of an AZ91D magnesium alloy.
20. The method of claim 9 wherein the forearm has a configuration
which adapts the forearm for use in a modular rifle having both a
lower receiver housing a trigger assembly and an upper receiver
securable to a barrel.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. 119(e) of
U.S. provisional patent application Ser. No. 61/863,195 filed on
Aug. 7, 2013 entitled MAGNESIUM GUN PARTS; U.S. provisional
application Ser. No. 61/846,674 filed on Jul. 16, 2013 entitled
EXTRUDED ALUMINUM FIREARM RECIEVER AND METHOD; and U.S. provisional
application Ser. No. 61/735,254 filed on Dec. 10, 2012 entitled
FIREARM RECEIVER AND METHOD OF MANUFACTURE, the disclosures of each
of which are hereby incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to firearms, parts thereof,
and methods of manufacturing such parts.
[0004] 2. Description of the Related Art
[0005] Firearms generally include three main parts, the barrel
through which a projectile, e.g., a bullet, is fired; the action
which includes the moving parts that provide for the loading,
firing, ejection of fired casing, and unloading; and either a stock
(shotguns and rifles) or grip (handguns). The receiver houses most,
if not all, of the operating parts that form the action of the
firearm. The receiver is often made out of steel or aluminum. Under
U.S. law, the receiver is generally the legally controlled part
that is considered to constitute the firearm itself and which has a
serial number fixed thereon.
[0006] Long arms, such as rifles and shotguns, will often have a
forearm which extends forward of the receiver and at least
partially surrounds the barrel. Typically, the forearm provides a
location for the user to grip the firearm with their off-hand.
While some forearms are positioned adjacent only the lower portion
of the barrel and do not completely encircle the barrel, it is also
known to use a forearm that completely encircles the barrel and
also serves as a barrel shroud. A barrel shroud protects the user
by inhibiting contact between the user and a barrel that has become
heated due to firing of the gun.
[0007] The barrel of the gun may either be in contact with the
forearm or be positioned proximate but slightly spaced from the
barrel. When the barrel is not in direct contact with the forearm,
it is generally referred to as a free floating barrel. Such free
floating barrels are typically secured to the receiver and this
attachment point serves as their sole point of attachment and
support. Free floating barrels are generally considered to be more
accurate than barrels which bear against the forearm because it is
thought that the pressure exerted on the barrel by the contact
between the barrel and forearm can change slightly from
shot-to-shot thereby causing inconsistent bullet flight paths. A
free floating barrel is not subject to such potentially variable
contact pressure. The barrel of a firearm is generally attached to
the receiver for both free-floating barrels and barrels which
contact the forearm of the gun.
[0008] While many firearms have a unitary receiver, some have
multiple receivers. For example, one common form of firearm, often
referred to as an AR-style rifle, has both an upper and lower
receiver which are detachably secured together. This type of rifle
gets its name from the AR-15 originally introduced by Armalite and
which was adopted by the U.S. military as the M-16 rifle. The M-16
is a selective fire weapon capable of both semi-automatic and fully
automatic operation. A civilian version of the M-16 capable only of
semi-automatic fire was subsequently developed by Colt's
Manufacturing Company and sold as the Colt AR-15. For AR-style
rifles, the lower receiver generally constitutes the serialized
component that is legally controlled as a firearm.
[0009] AR-style rifles are modular rifles which include an upper
receiver assembly having an upper receiver, a bolt carrier, a
barrel and a forearm. The forearm of AR-style rifles often takes
the form of a barrel shroud and, as a result, is commonly referred
to as a handguard. The lower receiver assembly includes a lower
receiver which houses a trigger assembly and has a port for
receiving a magazine. A pistol grip and stock can be attached to
the lower receiver.
[0010] The modular nature of the rifle provides several benefits.
For example, it allows the rifle to be easily customized for a
particular application. The modular nature of the rifle also allows
an individual component or one of the sub-assemblies to be easily
replaced if the original is damaged or an alternative design is
preferred. The many advantages provided by AR-style rifles, also
known as modern sporting rifles, have resulted in such rifles
becoming one of the most popular styles of firearm produced
today.
[0011] While conventional firearm designs and manufacturing
techniques are capable of producing satisfactory firearms, improved
cost-efficiency in the manufacture of firearms and design
modifications which improve the manufacturability remain
desirable.
SUMMARY OF THE INVENTION
[0012] The present invention provides a firearm forearm that
includes a magnesium alloy body and a method of manufacture. The
disclosed forearms are light weight and allow for the
cost-efficient manufacture of the forearms.
[0013] The invention comprises, in one embodiment thereof, a
firearm that includes a receiver operably coupled with a barrel and
a forearm securable to the firearm wherein the forearm includes a
magnesium alloy body.
[0014] The magnesium alloy body may advantageously be nickel
plated. An oven-cure ceramic coating can be applied to the nickel
plating. In some embodiments, the firearm is a modular rifle
wherein the receiver includes an upper receiver and a lower
receiver; the forearm and the barrel being mountable on the upper
receiver and the lower receiver housing a trigger assembly. The
barrel may be a free floating barrel that is spaced from the
forearm.
[0015] In some embodiments, the magnesium alloy body forms an outer
sleeve and the forearm further comprises an inner sleeve formed out
of a non-magnesium material, the outer sleeve being disposed about
and engaged with the inner sleeve. The inner sleeve may include a
steel material.
[0016] The forearm may be defined by a pair of separable parts
which substantially encircle the barrel when secured together.
Alternatively, the forearm may be a unitary forearm which
substantially encircles the barrel.
[0017] The invention comprises, in another form thereof, a method
of manufacturing a firearm forearm that includes forming a
magnesium alloy body and processing the magnesium alloy body to
form at least a portion of the forearm.
[0018] In some embodiments, the magnesium alloy body has a layer of
nickel plating formed thereon by a nickel plating process and a
ceramic coating is then applied on the layer of nickel plating.
[0019] The magnesium alloy body may be formed by thixotropically
molding the body. When thixotropically molding the body, the
magnesium alloy body advantageously has a surface roughness,
R.sub.a, that is between approximately 35 microinches and
approximately 60 microinches after molding and without any
post-molding processing to smooth the surface. Alternatively, the
step of forming a magnesium alloy body may include extruding the
magnesium alloy body.
[0020] In some embodiments, the extruded magnesium alloy body forms
a forearm that substantially encircles the barrel. After extruding
the magnesium alloy body, the body may be cut lengthwise to form
two separable parts of the forearm. The two separable parts
advantageously have the same configuration.
[0021] In some embodiments, the forearm includes an inner sleeve
and an outer sleeve disposed about the inner sleeve wherein the
magnesium alloy body forms the outer sleeve of the forearm and a
non-magnesium insert is provided to form the inner sleeve.
Advantageously, the magnesium alloy body forming the outer sleeve
is formed by extrusion.
[0022] The magnesium alloy body may be formed out of an AZ91D
magnesium alloy. In some embodiments, the forearm has a
configuration which adapts the forearm for use in a modular rifle
having both a lower receiver housing a trigger assembly and an
upper receiver securable to a barrel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above mentioned and other features of this invention,
and the manner of attaining them, will become more apparent and the
invention itself will be better understood by reference to the
following description of an embodiment of the invention taken in
conjunction with the accompanying drawings, wherein:
[0024] FIG. 1 is a side view of a firearm having a magnesium
forearm.
[0025] FIG. 2 is another side view of a firearm.
[0026] FIG. 3 is view of a firearm broken down into several major
sub-assemblies.
[0027] FIG. 4 is an exploded view of a lower receiver and extension
assembly, buttstock and grip.
[0028] FIG. 5 is a perspective view showing the removal of a two
piece forearm from a rifle.
[0029] FIG. 6 is an exploded view of an upper receiver, barrel and
two piece forearm.
[0030] FIG. 7 is a perspective view of a one piece forearm.
[0031] FIG. 8 is an exploded perspective view of a forearm with a
reinforcing insert.
[0032] FIG. 9 is an end view of a forearm with a reinforcing
insert.
[0033] FIG. 10 is an exploded end view of a two piece forearm.
[0034] FIG. 11 is an exploded perspective detail view of a two
piece forearm.
[0035] FIG. 12 is a schematic depiction illustrating the molding of
a forearm.
[0036] FIG. 13 is a schematic depiction illustrating the extruding
of a forearm.
[0037] FIG. 14 is a perspective view of an extrusion.
[0038] FIG. 15 is a cross sectional view of an extrusion die taken
along line A-A of FIG. 16.
[0039] FIG. 16 is an end view of an extrusion die.
[0040] FIG. 17 is a schematic depiction of a machining center for
the machining of a forearm.
[0041] FIG. 18 is a schematic cross section of a portion of a
forearm.
[0042] Corresponding reference characters indicate corresponding
parts throughout the several views. Although the exemplification
set out herein illustrates an embodiment of the invention, in one
form, the embodiment disclosed below is not intended to be
exhaustive or to be construed as limiting the scope of the
invention to the precise form disclosed.
DETAILED DESCRIPTION OF THE INVENTION
[0043] A firearm 30 having a lower receiver in accordance with the
present invention is shown in FIGS. 1 and 2. Firearm 30 is an
AR-style rifle and, except for the forearm assembly 70, has a
conventional design and construction which is well-known to those
having ordinary skill in the art.
[0044] FIG. 3 illustrates firearm 30 with several of the major
sub-assemblies being disconnected. More specifically, firearm 30
has been broken down to separate the lower receiver and extension
assembly 32, the upper receiver and barrel assembly 34, the bolt
and carrier group 36, and the charging handle 38. These
sub-assemblies, e.g., lower receiver and extension assembly 32 and
upper receiver and barrel assembly 34, can be further broken down
into still smaller modular assemblies.
[0045] FIG. 4 provides an exploded view of the lower receiver and
extension assembly 32. Illustrated in FIG. 4 are helical
compression spring 1, buffer assembly 2, hammer assembly 3, sear 4,
selector lever 5, helical compression spring 6, bolt catch plunger
7, bolt catch 8, spring steel pin 9, magazine catch 10, helical
compression spring 11, pin 12, helical compression spring 13,
magazine catch button 14, pivot pin 15, disconnector 16, trigger
assembly 17, screw 18, lock washer 19, grip 20, helical compression
spring 21, safety detent 22, grooved pins 23, grooved pin 24,
takedown pin 25, stepped spacer 26, buttstock assembly 27,
self-locking screw 28, receiver extension tube 29 and lower
receiver 40. The assembly and operation of the parts shown in FIG.
4 will be understood by those having ordinary skill in the art.
[0046] The upper receiver and barrel assembly 34, which includes a
forearm, is shown in greater detail in FIGS. 5 and 6. The
illustrated forearms are adapted for use with AR style rifles and
also function as a heat shield and as a handguard, however,
alternative embodiments can be employed with other firearms. The
terms handguard and forearm are used interchangeably herein.
[0047] The forearm assembly shown in FIGS. 5 and 6 is a two-piece
assembly 70a having a pair of separable parts 72a that encircle the
barrel. FIG. 5 illustrates the removal from rifle 30 of one of the
two handguards 72a that form forearm 70a. FIG. 6 is a view of upper
receiver and barrel assembly 34 with the handguard assembly 70a
detached from assembly 34. Assembly 34 includes the upper receiver
33 which is secured to barrel 35. A slip ring assembly 64 is
mounted proximate the attachment of barrel 35 to upper receiver 33
and a front sight assembly 66 is mounted on barrel 35 near muzzle
68.
[0048] Handguards 72a are removed from rifle 30 by pressing slip
ring 64 toward upper receiver 33 and away from front sight 66. Slip
ring 64 is biased toward muzzle 68 and front sight 66 by a spring
(not shown). Slip ring 64 surrounds a reduced diameter collar 74 on
handguards 72a. After depressing slip ring 64, one of the
handguards 72a can be removed by pivoting the released end of the
handguard 72a away from barrel 35 and disengaging handguard 72a
from handguard cap 76. Handguards 72a may have retaining tabs (not
shown) which fit within openings or recesses in cap 76 or otherwise
engage cap 76 to thereby secure the muzzle end of handguard
assembly 70a. FIG. 5 illustrates one person pressing down on slip
ring 64 and a second person removing a handguard 72a, however, it
is will generally be possible for a single individual to remove
handguard assembly 70a without assistance. To attach the handguards
72a, the process is reversed.
[0049] Alternative method of attaching the forearm may also be
employed. For example, the forearm could be provided with helical
threads for securely engaging the firearm or a groove which
receives a retractable projection. In still other embodiments, the
forearm could be provided with apertures through which fasteners
are extended to secure the forearm to the firearm. Other suitable
methods of securing the forearm to the firearm may also be
employed.
[0050] As can be understood with reference to FIGS. 5 and 6,
handguard assembly 70a substantially encircles barrel 35 with each
of the two similarly configured handguards 72a engaging each other
along surfaces 80 that extend along the length of barrel 35. Vent
openings 78 in handguards 72a allow air to escape and thereby
dissipate heat from the space between barrel 35 and handguard
assembly 70a.
[0051] It is noted that the handguard assembly 70a depicted in
FIGS. 5 and 6 has a slightly tapered configuration wherein the
diameter of the handguard assembly 70a is largest near upper
receiver 33 (excluding collar 74) and becomes progressively smaller
toward cap 76. In this regard, it is also noted that the handguard
assembly 70 shown in FIGS. 1 and 2 also has a tapered shape. The
handguard assembly of FIGS. 1 and 2 differs from the assembly of
FIGS. 5 and 6 by having an exterior surface with a plurality of
recesses while the assembly of FIGS. 5 and 6 has a generally smooth
exterior surface. The recesses on the assembly of FIGS. 1 and 2
enhance the ability of the user to securely grip the forearm.
[0052] The handguard assemblies illustrated in FIGS. 3, 7, 8, 9, 10
and 11 are not tapered and have a more cylindrical configuration.
It is further noted that while the handguard assembly of FIGS. 5
and 6 are two piece handguards, the handguard assemblies of FIGS.
7, 8 and 9 are unitary handguards. The unitary handguard assemblies
have a tubular form and must be slid into place either before
barrel 62 is attached to upper receiver 60 or before the front
sight assembly 66 is mounted on barrel 62 (if a front sight
assembly is being used). The mounting of the handguard assembly on
the rifle, whether a two piece or unitary design, will depend on
the particular details of the rifle design as will be
well-understood by a person having ordinary skill in the art.
[0053] Handguard assembly 70b shown in FIG. 7 is a unitary
handguard and has a plurality of vent openings 86 formed therein.
Handguard 70b also includes an interior threaded portion (not
shown) for securing handguard 70b to upper receiver 60. Lugs 88 may
be used to secure a bipod or other device to handguard 70b. The
interior threads are located at the same end as lugs 88. Handguard
70b also includes four sections of a mounting rail such as a
Picatinny rail. In the embodiment of FIG. 7, the top and bottom
sections 82a, 82b extend for substantially the entire length of
handguard 70b while the side sections 82c extend only a portion of
the length.
[0054] Mounting rails 82a-82c provide a standardized mounting
feature for attaching accessories, such as a scope or light source,
to the forearm. Picatinny rails are one of the more common types of
mounting rail and are also known as MIL-STD-1913 rails and have
generally T-shaped cross section with a series of spaced slots 84.
Those having ordinary skill in the art will recognize that the
shape of such rails has been standardized to allow for the
attachment of a wide variety of different accessories and that the
use of such rails on the forearm of an AR style rifle and other
firearms is a common and known practice.
[0055] FIGS. 8 and 9 illustrate a variant of FIG. 7. The embodiment
illustrated in FIG. 7 is a unitary handguard that is made entirely
out of magnesium. The handguard assembly 70c illustrated in FIGS. 8
and 9 has a magnesium outer sleeve 85 and an inner reinforcing
sleeve 83 which is formed out of a stronger material. For example,
inner sleeve 83 may be a steel or aluminum tube. In this regard, it
is noted that some magnesium alloys have a greater strength than
others. The embodiment illustrated in FIG. 7, for example, can be
manufactured using an AZ91B magnesium alloy without the use of a
reinforcing tube. Other magnesium alloys, AZ91D, for example, do
not have physical properties which are identical to AZ91B and may
require a reinforcing sleeve 83. The need for a reinforcing sleeve
is dependent not only on the material used to form the outer sleeve
but also on the dimensions and configuration of the forearm. Not
all forearms using an AZ91D alloy will necessarily require the use
of reinforcing sleeve nor will all forearms using an AZ91B alloy
necessarily be sufficiently strong without an insert. Moreover, it
may be desirable to provide additional strength to the forearm
through the use of a reinforcing sleeve 83 even if the material
used to form the outer sleeve would be strong enough without such a
sleeve.
[0056] When using a reinforcing sleeve 83, the outer radial surface
83a of reinforcing sleeve 83 contacts the inner radial surface 85a
of outer sleeve 85 over a substantial portion of the surfaces 83a,
85a which face each other. The illustrated embodiment includes an
inner sleeve 83 with vent openings 86a which align with the vent
openings 86 of outer sleeve 85. The illustrated inner sleeve 83 and
outer sleeve 85 also have the same length. Alternative embodiments,
however, may employ different arrangements of the inner and outer
sleeve. For example, the outer sleeve could include vent openings
that expose a portion of the inner sleeve or the two sleeves could
have differing lengths. It may also be desirable in some
embodiments for the inner sleeve to have more openings than the
outer sleeve to reduce the weight of the inner sleeve while still
providing the desired reinforcing strength or the inner sleeve
might not include any vent openings. Although the two sleeves could
be slidingly engaged and not fixed together, it will generally be
desirable to permanently secure the two sleeves 83, 85 together.
The two sleeves 83, 85 can be secured together using welds, a
press-fit engagement, or other appropriate method.
[0057] FIGS. 10 and 11 illustrate another variant of the forearm of
FIG. 7. The embodiment of FIGS. 9 and 10 is formed by taking the
forearm of FIG. 7 and cutting it in half to form a two piece
handguard assembly 70d having a pair of separable parts 72d that
encircle the barrel when secured together. Each of the two
resulting handguards 72d have engagement surfaces 90 which abut
with surfaces 90 of the opposing handguard 72d when the two
handguards 72d are secured about a barrel 35. The two handguards
72d can be secured together using various methods known in the art
such that described above with regard to the embodiment of FIGS. 5
and 6. The embodiment of FIGS. 9 and 10, however, use threaded
fasteners. As seen in FIG. 10, an access area 96 and an aperture 98
are cut in the handguards 72d and threaded fasteners 92 are engaged
with nuts 94 to secure the two handguards 72d together to form
handguard assembly 70d, for example, four sets of fasteners 92 and
nuts 94 can be used to secure the handguards 72d. It is also noted
that instead of using a loose nut 94, threaded inserts could be
embedded in one of the handguards 72d to engage threaded fasteners
92.
[0058] A variety of other modifications can also be made to the
illustrated handguard assemblies. For example, AR style rifles
originally all used a gas impingement system to cycle the spent
shell casing and load a new round into the chamber. In a gas
impingement system, propellant gases are bled from a port in the
barrel into a tube which conveys the pressurized gas to a location
where it can impinge upon the bolt carrier and perform the cycling
operation. In recent years, a number of manufacturers have begun
manufacturing AR style rifles with a gas piston system. In this
alternative, pressurized gases are bled from the barrel through a
port and impinge upon a piston. A rod connected to the piston is
used to impinge upon the bolt carrier. In gas piston systems, the
hot and dirty propellant gases are not introduced into the receiver
to thereby reduce fouling of the action of the firearm. Because the
tube conveying the gases or the piston and rod assembly acted upon
by the propellant gases is typically located alongside barrel 35
for AR style firearms, the configuration of the handguard assembly
will often be influenced by whether the firearm is using a gas
impingement or gas piston system. Various configurations of
handguards suitable for use with gas impingement systems and gas
piston systems are well known to those having ordinary skill in the
art and can be employed with alternative embodiments of the present
invention.
[0059] The illustrated handguards can be formed by injection
molding a thixotropic, semisolid magnesium alloy and subsequently
applying a nickel coating using an electroless nickel plating
process. In this regard, it is noted that handguards for AR-style
rifles are most commonly formed out of aluminum or plastic.
Magnesium is lighter than aluminum and comparable in strength. For
example, lightweight magnesium alloys may be 35% lighter than
aluminum alloys. Although plastic is lighter than magnesium,
magnesium is significantly stronger.
[0060] As mentioned above, magnesium alloys such as AZ91B and AZ91D
can be used when molding the illustrated handguards. The
composition of an AZ91B magnesium ally may include by weight 8.3 to
9.7% Al, 0.13% Mn min., 0.35 to 1.0% Zn, 0.50% Si max., 0.35% Cu
max, 0.03% Ni max, and 0.30% max other (total) with Mg forming the
balance of the alloy. The composition of an AZ91D magnesium alloy
may include by weight 8.5-9.5% Al, 0.45-0.90% Zn, 0.17-0.4% Mn,
.ltoreq.0.05% Si, .ltoreq.0.025% Cu, .ltoreq.0.001% Ni, and
.ltoreq.0.004% Fe with Mg forming the balance of the alloy.
Magnesium alloys such as AZ91B and AZ91D are commercially available
and well-known to those having ordinary skill in the art.
[0061] The use of a thixotropic injection molding process to form
handguard assemblies 70a-70d is schematically depicted in FIG. 12.
Molding machine 100 includes a supply system 102 for feeding
magnesium chips and an inert gas supply 104. The introduction of an
inert gas such as argon prevents the magnesium from igniting. The
magnesium chips and inert gas are fed into an injector barrel
housing a screw 106. Heating elements 108 heat the content of the
barrel. Heating elements 108 partially melt the magnesium chips
while screw 106 provides the shearing force necessary to create a
thixotropic slurry out of the semi-molten magnesium. Injector
mechanism and accumulator 110 accumulate and then force the
thixotropic magnesium into mold 112 under high pressure. After
allowing the magnesium to cool within mold 112, the mold is opened
to remove the forearm.
[0062] Thixotropic injection molding typically provides a laminar
melt flow at a relatively low temperature which provides for quick
cooling with limited shrinkage and high dimensional accuracy.
Thixotropic injection molding also typically results in relatively
high densities and low porosity. The dimensional stability and
tight tolerances obtainable by thixotropic injection molding is
result of several factors including laminar flow of the thixotropic
slurry into the mold, the high pressures used when filling the mold
and rapid solidification. The high dimensional stability, tight
tolerances and low draft obtainable by thixotropic injection
molding of a magnesium alloy allows for the molding of complex
geometries.
[0063] The molded handguards also have a semi-smooth surface. After
molding, and without any post-molding processing, it is possible to
obtain a surface having a surface roughness, R.sub.a, of
approximately 35 microinches to approximately 60 microinches
(approximately 0.00089 mm to approximately 0.0015 mm) when
thixotropically molding a magnesium alloy. The semi-smooth skin and
ability to mold complex geometries held to tight tolerances, allow
handguards to be molded with preformed openings and other design
features that might otherwise require significant machining to
form. Furthermore, for those features that are machined, magnesium
is a relatively easy material to machine.
[0064] Minimizing the machining of the handguards is advantageous
not only for reasons of manufacturing efficiency but also because
it reduces the small particles of magnesium that are generated
during the machining process. Small particles of magnesium are
relatively easily ignited and thus must be carefully handled.
Minimizing the volume of such particles is advantageous.
[0065] In the illustrated embodiments, it is noted that the general
structure of Picatinny rails 82a-82c can be formed by the molding
operation with Picatinny rail slots 84 and other engagement
surfaces of the Picatinny rails 82a-82c being machined after the
molding operation. It may also be advantageous to roughly mold
slots 84 in rails 82a-82c and clean up the surfaces with
post-molding machining operations. While it may also be possible to
form rails 82a-82c by the molding operation alone and without any
post-mold machining, it will generally be desirable to machine the
engagement surfaces of rails 82a-82c to obtain tightly controlled
tolerances. Vent openings in the handguards are advantageously
formed by molding but could alternatively be subject to limited
post-molding machining or formed entirely by post-molding machining
operations.
[0066] FIG. 17 schematically depicts a CNC machining center 184
that can be used to machine the magnesium alloy bodies forming the
handguards to achieve the desired final shape. The illustrated CNC
machining center 184 includes a workbed 186. A carriage 188 allows
tooling 190 to be repositioned relative to workbed 186. A
controller 192 controls the operation of the tooling 190. Various
other machining equipment known in the art can also be used when
machining the handguard assemblies.
[0067] After molding and machining the handguard, it is tumbled in
a ceramic media for deburring, then cleaned and plated. Either an
electroplating or electroless plating process can be used to plate
the handguard. Plating the magnesium body protects the magnesium
from corrosion, notably galvanic corrosion.
[0068] Although electroplating can be employed, an electroless
nickel plating process provides several advantages. Electroless
nickel plating is an auto-catalytic chemical process that deposits
a nickel-phosphorus layer on the magnesium components of the
handguards. In an electroless nickel plating process, a reducing
agent is used to react with metal ions to deposit metal on the
object being plated. In the illustrated example, a layer of nickel
is deposited on the handguards. Unlike electroplating, electroless
nickel plating does not require the use of an electrical current to
form a deposit on the work piece. The absence of flux-density and
power supply variations allows the electroless nickel plating
process to provide a more even deposit on complex geometry than
would an electroplating process. The use of an electroless nickel
plating process also provides the handguard with a more durable
coating than would a conventional ion-exchange chromating
process.
[0069] Once plated, the handguard can be assembled in a firearm 30.
If the handguard will be combined with an inner sleeve, the inner
sleeve and outer magnesium sleeve will be combined before
installing on the firearm 30. The electroless nickel plating also
allows for the application of one or more additional layers of
material such as those applied to firearm components made out of
traditional materials. For example, another layer of plated
material using traditional plating methods could be applied to the
electroless nickel plating layer. Alternatively, it may be desired
to apply a camouflage pattern to the handguard. Materials and
methods of applying camouflage patterns to firearms is well-known
in the art.
[0070] An oven-cure ceramic coating can be applied to the nickel
plating to provide it with the desired color and/or camouflage
pattern as well as enhance the wear and weather resistance of the
forearm. For example, a Cerakote.TM. coating commercially available
from NIC Industries, Inc. located in White City, Oreg. can be
applied over the electroless nickel plating layer and form the
exterior layer of the handguards. The application of various other
material layers to enhance the appearance, wear or weather
resistance of a firearm that can be applied to a nickel plated
surface using traditional methods are also well known to those
having ordinary skill in the art.
[0071] FIG. 18 schematically depicts a cross section of a portion
of a forearm and the thickness of layers 122 and 124 is exaggerated
for purposes of graphical clarity. As can be seen in FIG. 18, a
magnesium alloy body 120 forms the structure of the illustrated
portion of the forearm and has a layer of plating 122 deposited
thereon. In the illustrated embodiment plating layer 122 is a layer
of nickel plating. Deposited on top of plating 122 is a layer of
ceramic coating 124. In the illustrated embodiment, both the
plating layer 122 and ceramic coating 124 are applied to all
surfaces of the magnesium alloy body 120. It will generally be
desirable to apply a plating layer 122 to all surfaces of the
magnesium body 120. Ceramic coating 124 can also be advantageously
applied to all external surfaces of the magnesium body as
exemplified in the illustrated embodiment. In some embodiments,
however, it may be desirable to be more selective as to which
surfaces receive plating 122 and ceramic coating 124. For example,
it may be desirable to omit either plating 122 or coating 124 from
the inner surface of a magnesium alloy body forming the outer
sleeve of a forearm that receives an inner sleeve.
[0072] Turning now to FIGS. 13-16, another method of manufacturing
a handguard/forearm will be discussed. The method illustrated by
FIGS. 13-16 involves the extrusion of the forearm. FIG. 13
schematically depicts an extruder 170 that can be used to form an
extrusion having the shape of unfinished forearm 162 in FIG. 14.
Extruder 170 includes a hydraulic press 171 which powers a ram 172.
Ram 172 extends into container 174 which holds a billet 176 of the
material to be extruded. A dummy block, not shown, is placed
between billet 176 and ram 172. A die 180 is installed at the end
of container 174 opposite ram 172. Controls 178 govern the
operation of extruder 170. As ram 712 is extended, billet 176 is
forced through die 180 to form an extrusion with the configuration
of unfinished forearm 162.
[0073] When using an extruder, the billet may either be cold or
heated. In a cold extrusion process, the billet is placed in the
container in a solid form at ambient temperature. Alternatively,
the billet may be heated before it is placed in the container. In a
hot extrusion process, the billet is heated to a temperature above
the recrystallization temperature of the material. In a warm
extrusion process, the billet is heated to a temperature above the
ambient temperature but below the recrystallization temperature of
the material.
[0074] Although magnesium alloys can be cold extruded, when forming
an extruded forearm a warm or hot extrusion process is
advantageously employed. For example, the billet may be an AZ91D
magnesium alloy. The composition of AZ91D magnesium alloys is known
in the art and typically includes about 8.5-9.5% Al, 0.45-0.90% Zn,
0.17-0.4% Mn, .ltoreq.0.05% Si, .ltoreq.0.025% Cu, .ltoreq.0.001%
Ni, and .ltoreq.0.004% Fe with Mg forming the balance of the alloy.
This alloy has high strength and good corrosion resistance and is
often used for the housings of electric appliances.
[0075] FIG. 14 illustrates an unfinished forearm 162 that can
produced by extruder 170. As can be seen in this figure, unfinished
forearm 162 defines an axially extending centerline 164. Unfinished
forearm 162 has a cylindrical section 165 that extends parallel
with and concentrically about centerline 164. T-shaped projections
166 extend outwardly from cylindrical portion 165 and will define a
mounting rail such as a Picatinny rail in the finished forearm.
Cylindrical section 165 also defines an axially extending center
bore through which barrel 35 will extend when the forearm is
mounted on a firearm 30.
[0076] When forming an extrusion with extruder 170, the extrusion
may have an axial length parallel with centerline 164 that is
equivalent to or slightly longer than a single forearm by selecting
an appropriately sized billet 176. Advantageously, a larger billet
176 is used and the extrusion has an axial length that is longer
than a single forearm and equivalent to or slightly longer than a
whole number of individual forearms whereby the extrusion can be
cut transverse to centerline 164 to thereby form a plurality of
forearms from a single extrusion. Each of the individual unfinished
forearms 162 can then be machined to form a finished forearm. The
use of a billet having a size sufficient to form several forearms
from a single extrusion will generally provide manufacturing
efficiencies over the use of a billet sufficient only for a single
forearm.
[0077] As depicted in FIG. 14, unfinished forearm 162 has a bore
168 formed therein during the extrusion process. FIGS. 15 and 16
schematically depict a die 180 which can be used to form an
extrusion having a bore extending therethrough. As is known in the
art, a mandrel can be used to form a centrally located opening in
an extrusion. The illustrated die 180, includes a mandrel 194
having support legs 196 and a leading edge 198. The billet first
contacts leading edge 198 and is pierced thereby. The support legs
196 support center die 200 which forms center bore 168. Support
legs 196 are located only proximate the leading edge of die 180 and
allow the material to reform within die 180 after passing by legs
196. Depending upon the precise parameters of the extrusion
process, the finished extrusion may include weld lines at the
location of legs 196 as a result of the extrusion process. Once the
extrusion is formed and has cooled, it is cut to length to form a
plurality of unfinished forearms 162.
[0078] After forming unfinished forearm 162, it is machined to form
a forearm having the desired configuration similar to the machining
of a molded handguard. FIG. 17 schematically depicts a CNC
machining center 184 that can be used to machine an unfinished
forearm 162 to its desired final shape.
[0079] When forming the embodiment of FIGS. 10 and 11, unfinished
forearm 162 is cut in half parallel with center line 164. The
general structure of mounting rails 82a-82c are formed by the
extrusion process with slots 84 and other engagement surfaces of
mounting rails 82a-82c being machined to meet final tolerances
after the extrusion operation.
[0080] After machining the extruded forearm, it is tumbled in a
ceramic media for deburring, then cleaned and provided with a
surface finish in same manner as a molded forearm as discussed
above. Once the surface of the forearm has been given the desired
finish, the forearm is completed can be assembled in a firearm
30.
[0081] Extruded and molded forearms will generally be machined and
finished in the same manner. The configuration of the forearm,
however, may make it more suitable for one process or the other.
For example, tapered forearms, such as 70, 70a shown in FIGS. 1, 2,
5 and 6, are more easily molded while forearms having a cross
section, taken transverse to centerline 64, that remains relatively
constant over the axial length of the forearm, such as those shown
in FIGS. 3, 7-10 and 14, are more suitable for extrusion.
[0082] In this regard, it is noted that both types of forearms can
be formed using either process. However, if a tapered forearm is
extruded, a substantially amount of material would have to be
removed by machining thereby significantly impacting the efficiency
of the process. The molding of a tubular forearm well suited for
extrusion would not present undue inefficiencies, however, even
greater efficiencies will generally be obtainable by extruding such
forearms.
[0083] For both molding and extrusion processes, the unfinished
forearm resulting from the molding or extrusion process reduces the
amount of machining required and will generally give the forearm
its final profile. The forearm is then machined to meet the desired
final tolercances. After the machining, the forearm is plated using
an electroplating or electroless plating process to protect the
magnesium material from corrosion such as galvanic corrosion. The
plating layer can function as the final finish layer of the forearm
or a surface finish, such as an oven-baked ceramic coating, can be
applied over the plating layer to give the product its final finish
and color.
[0084] It is noted that the finished forearm may be used in the
assembly of a new firearm 30 or be supplied as an aftermarket part.
When supplied as an aftermarket part, the forearm allows owners of
pre-existing firearms 30 to remove the original forearm, such as an
aluminum or plastic forearm, and replace it with a forearm in
accordance with the present disclosure.
[0085] While the present invention has been illustrated and
described in the context of a handguard/forearm for an AR-style
rifle, the present invention may be utilized with other firearm
components, such as scope rings, butt stocks, grips and the like
and with firearm components for other styles of firearms. The
invention is not limited to the exemplary design described herein
and the present invention may be further modified within the spirit
and scope of this disclosure. This application is therefore
intended to cover any variations, uses, or adaptations of the
invention using its general principles.
* * * * *