U.S. patent number 3,771,415 [Application Number 05/224,208] was granted by the patent office on 1973-11-13 for rifle conversion assembly.
This patent grant is currently assigned to Colt Industries Operating Corp.. Invention is credited to Richard L. Costello, Henry A. Into.
United States Patent |
3,771,415 |
Into , et al. |
November 13, 1973 |
RIFLE CONVERSION ASSEMBLY
Abstract
An assembly is provided for converting a firearm of standard
caliber to one of a smaller caliber and includes a conversion
chamber adaptor with a bolt mounted for movement between recoil and
battery positions. A backplate damper assists in maintaining the
operating components in assembly and absorbs recoil impact energy
of the recoiling mass upon firing of the weapon. When the
conversion assembly is installed in a weapon having a buffer
disposed rearwardly of its chamber, the backplate damper
additionally serves to transmit that energy to the buffer.
Inventors: |
Into; Henry A. (Hartford,
CT), Costello; Richard L. (Hartford, CT) |
Assignee: |
Colt Industries Operating Corp.
(Hartford, CT)
|
Family
ID: |
22839703 |
Appl.
No.: |
05/224,208 |
Filed: |
February 7, 1972 |
Current U.S.
Class: |
89/16; 42/25;
89/29; 89/197; 42/16; 42/49.02; 89/128; 89/198 |
Current CPC
Class: |
F41A
3/78 (20130101); F41A 11/02 (20130101); F41A
15/14 (20130101) |
Current International
Class: |
F41A
11/00 (20060101); F41A 15/14 (20060101); F41A
3/78 (20060101); F41A 15/00 (20060101); F41A
11/02 (20060101); F41A 3/00 (20060101); F41c
021/12 () |
Field of
Search: |
;42/77
;89/14R,16,29,128,194,197,198,199 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,428,611 |
|
Nov 1968 |
|
DT |
|
1,093,265 |
|
Nov 1960 |
|
DT |
|
Primary Examiner: Bentley; Stephen C.
Claims
We claim:
1. A firearm conversion assembly detachably insertable into a
chamber of a firearm receiver upon removal of its standard bolt
means for converting the firearm to fire ammunition of a caliber
smaller than its standard caliber and comprising a conversion
chamber adaptor insertable into the firearm chamber in fixed
relation thereto, a bolt, a backplate damper, detachable mounting
means releasably mounting the adaptor, bolt and backplate damper in
a unitary assembly and including a guide rod detachably connecting
the bolt and the backplate damper in assembled relation and
supporting the bolt and the backplate damper on the guide rod, the
bolt and the backplate damper being reciprocable on the guide rod
with the bolt movable between a forward battery position in
engagement with the conversion adaptor and a rear recoil position,
the guide rod establishing a rear limit position for the backplate
damper and cooperating therewith in establishing the rear recoil
position of the bolt, and an action spring supported on the guide
rod with opposite ends of the spring seated on the bolt and the
backplate damper, the spring urging the bolt forwardly toward
battery position and urging the backplate damper toward its rear
limit position, the backplate damper being engageable with the bolt
and serving to absorb recoil impact energy of the recoiling mass
when the bolt moves from battery to recoil positions.
2. The assembly of claim 1 in combination with a firearm having a
buffer engageable with the backplate damper upon installation of
the conversion assembly into the firearm chamber, wherein the
backplate damper is urged a predetermined distance forwardly of its
rear limit positions by the firearm buffer when the bolt is in
battery position for minimizing rebound of the bolt during its
movements between battery and recoil positions.
3. The assembly of claim 1 wherein the backplate damper includes a
lug receiving locating slot for locating and retaining the
conversion assembly in operative position relative to the firearm
receiver.
4. The assembly of claim 3 further including a modified conversion
magazine having an upstanding lug, the conversion adaptor having a
bottom surface with a lug receiving locating slot which cooperates
with the magazine lug, upon mounting the magazine in the firearm
receiver, for locating and retaining the conversion ssembly in
operative position relative to the firearm receiver.
5. The assembly of claim 1 wherein the bolt is an elongated member
having an axially extending firing pin passageway, a firing pin is
received in the passageway for reciprocating movements between
forward and rear positions, a hammer actuated striker is mounted in
the bolt for movement between forward and rear operative limit
positions, a return coil spring is concentrically received in the
passageway about the firing pin for urging it toward its rear
position and biasing the striker toward its rear limit position for
hammer engagement, and a sleeve is received in the passageway
surrounding the firing pin and having an annular front wall serving
as a return spring seat.
6. The assembly of claim 1 wherein the bolt is an elongated member
carrying a cartridge rim-engaging extractor and cartridge
wall-engaging ejector assist member, the extractor and the ejector
assist member each being supported on the bolt for pivotal movement
toward and away from the major longitudinal axis of the bolt,
spring means in the bolt normally biasing the extractor and the
ejector assist member toward the central longitudinal axis of the
bolt, the conversion adaptor having a rear face with a cartridge
chamber extending axially forwardly therefrom, and first and second
ramp surfaces formed in the adaptor and diverging from the rear
face of the conversion adaptor radially outwardly of its chamber
for camming the extractor and ejector assist member radially
outwardly when the action spring moves the bolt into battery in
engagement with the rear face of the conversion adaptor.
7. A firearm conversion assembly detachably insertable into a
chamber of a firearm receiver upon removal of its standard bolt
means for converting the firearm to fire ammunition of a caliber
smaller than its standard caliber and comprising a conversion
chamber adaptor insertable into the firearm chamber in fixed
relation thereto, a bolt, a backplate damper, mounting means
including a pair of guide rods threadably fixed to the adaptor and
supporting the bolt and the backplate damper for reciprocable
movement, the bolt being reciprocable between a forward battery
position in engagement with the conversion adaptor and a rear
recoil position, at least one of the guide rods establishing a rear
limit position for the backplate dampler and cooperating with the
backplate damper in establishing the rear recoil position of the
bolt, an action spring mounted on one of the guide rods between the
bolt and the backplate damper urging the bolt forwardly toward
battery position and urging the backplate damper toward its rear
limit position, the backplate damper being engageable with the bolt
and serving to absorb recoil impact energy of the recoiling mass
when the bolt moves from battery to recoil positions, the guide
rods detachably securing the conversion assembly components in an
integral unit for quick and easy installation and removal relative
to the firearm receiver.
8. A firearm conversion assembly detachably insertable into a
chamber of a firearm receiver upon removal of its standard bolt
means for converting the firearm to fire ammunition of a caliber
smaller than its standard caliber and comprising a conversion
chamber adaptor insertable into the firearm chamber in fixed
relation thereto, an elongated bolt including an axially extending
firing pin passageway having concentric passageway portions with a
rear maximum diameter portion, a forward reduced diameter portion
and an interconnecting portion therebetween of intermediate
diameter size, a firing pin in the passageway reciprocable between
forward and rear positions, the firing pin having a radially
enlarged end flange received in the maximum diameter passageway
portion and a shank extending into the forward passageway portion
and merging with said end flange with a smoothly contoured fillet
radius, a hammer actuated striker received in the rear maximum
diameter passageway portion of the bolt for movement between
forward and rear operative limit positions, a return coil spring
concentrically received in the passageway about the firing pin for
urging it toward its rear position and biasing the striker toward
its rear limit position for hammer engagement, a sleeve received in
the passageway surrounding the firing pin shank and having an
annular front wall serving as a return spring seat, the sleeve
confining the return spring within the intermediate passageway
portion between the front wall of the sleeve and an abutment formed
at the juncture between the intermediate and forward passageway
portions, mounting means mounting the bolt for reciprocable
movement between a forward battery position in engagement with the
conversion adaptor and a rear recoil position, a backplate damper
supported by the mounting means in a position disposed rearwardly
of the bolt, and an action spring between the bolt and the
backplate damper urging the bolt forwardly toward battery position,
the backplate damper being engageable with the bolt and serving to
absorb recoil impact energy of the recoiling mass when the bolt
moves from battery to recoil positions.
Description
This invention generally relates to gas operated firearms and
particularly to a conversion assembly for converting a firearm to
fire smaller size ammunition.
A primary object of this invention is to provide a new and improved
conversion assembly of a compact, rugged construction which may be
quickly and easily manufactured at relatively low cost and which is
suited for converting standard weapons such as rifles to fire a
relatively inexpensive bullet of smaller caliber for training
purposes and the like.
Another object of this invention is to provide a new and improved
conversion assembly featuring a combination backplate and damper
device which not only assists in maintaining the conversion
components in assembly but also absorbs and transmits bolt recoil
impact energy to a buffer of the firearm in which the assembly is
installed.
A further object of this invention is to provide a conversion
assembly of the type described having a new and improved cartridge
ejector and extractor arrangement.
Another object of this invention is to provide such a conversion
assembly having a new and improved firing pin arrangement
particularly suited to minimize any tendency of hammer blows to
weaken or fracture thin portions of the firing pin shank. Included
in this object is the aim of permitting a relatively large fillet
radius between the shank and an enlarged head of the firing pin to
further minimize undesired failures and at the same time to
eliminate any spreading of its return spring coils and binding of
the pin.
Other objects will be in part obvious and in part pointed out in
more detail hereinafter.
A better understanding of the objects, advantages, features,
properties and relationships of this invention will be obtained
from the following detailed description and accompanying drawings
which set forth an illustrative embodiment and is indicative of the
way in which the principle of this invention is employed.
In the drawings:
FIG. 1 is a fragmentary side elevational view, partly broken away
and partly in section, of a rifle with a conversion assembly
incorporating this invention shown installed in the rifle and
illustrated in a battery positipn;
FIG. 2 is a side view, partly broken away and partly in section,
showing certain details of a bolt and modified magazine of the
conversion assembly of FIG. 1 illustrated in a recoil position;
FIG. 3 is an enlarged view, partly in section, showing a front face
of the bolt;
FIG. 4 is an enlarged view, partly broken away and partly in
section, of the bolt taken generally along lines 4--4 of FIG. 3 and
shown in an intermediate recoiling position relative to a
conversion chamber adaptor; and
FIG. 5 is an enlarged view, partly in section, showing a rear face
of the bolt.
Referring now to the drawings in detail, a preferred embodiment of
this invention is shown incorporated in a conversion assembly
generally designated 10. It will be understood that while the
conversion assembly is shown installed in a gas operated automatic
rifle 12 for purposes of illustration, the conversion assembly 10
of this invention is readily adapted for use in other firearms of a
magazine fed, gas operated type which fire from closed bolt
position.
To convert the illustrated rifle 12 to fire ammunition of a smaller
caliber in the rifle 12 which is chambered for a larger, more
expensive caliber bullet, the conversion assembly 10 is installed
after a standard bolt carrier group (not shown) of the rifle 12 has
been removed. This is accomplished by simply removing the standard
rifle magazine from lower receiver 14, pushing out a takedown pin
16 interconnecting the lower receiver 14 to upper receiver 18 and
swinging the lower receiver 14 downwardly about pivot pin 20. The
standard bolt carrier group may then be withdrawn rearwardly from
the upper receiver 18 of the opened weapon and the conversion
assembly 10 may be installed.
To facilitate such installation and to ensure ease in removing and
otherwise handling the conversion assembly 10 without requiring any
loose parts, detents, thumb screws, etc. normally associated with
devices of this type, the replacement components to be substituted
for the standard bolt carrier group to effect the desired
conversion are designed as an integral one-piece unit.
This unit includes a conversion chamber adaptor 22 having suitable
lugs 24 engageable with conventional bolt locking lugs 26 on a
breech end of barrel 28 upon inserting and rotating the adaptor 22
within rifle chamber 30 to lock the adaptor 22 in operative
position. (An upper adaptor lug preferably engages an interior
receiver wall 18a for guiding the assembly 10 during its
installation and removal.) Upon adaptor 22 being moved home into
the rifle chamber 30, e.g., the assembly 10 is rotated and an upper
lug is angularly moved into a generally vertical position with the
adaptor lugs 24 lockingly engaged with the bolt locking lugs 26 of
the rifle chamber 30. The adaptor 22 has a chamber 32 extending
axially forwardly of its rear face 34, and the chamber 32 is bored
for a caliber, such as a 0.22 long rifle, e.g., which is smaller
than the standard caliber of rifle 12.
A bolt 36 is supported for reciprocating movement between a battery
position (shown in FIG. 1 with the bolt 36 engaging rear face 34 of
adaptor 22) and a rear recoil position (FIG. 2) and is supported
for such movement on a pair of guide rods 38, 40 received in
exposed longitudinally extending grooves 42, 44 of generally "U"
shaped cross-section formed in generally diametrically opposed
sides of the bolt 36, preferably in a plane disposed at an angle to
the horizontal as best seen in FIGS. 3 and 5. The guide rods 38, 40
are suitably fixed to a rear portion of adaptor 22, as by the
illustrated threaded connection, and extend axially rearwardly from
the adaptor 22 to a position adjacent a buffer 46 of the rifle 12.
The buffer 46 is reciprocably mounted in a tubular body of the
lower receiver 14 and is biased forwardly by a spring 48 into a
normal position illustrated in FIG. 1. In the specifically
illustrated embodiment, guide rods 38, 40 terminate in radially
enlarged heads as seen at 50 in FIG. 1 which is disposed in
forwardly spaced adjacent relation to the buffer 46 within the
confines of a backplate damper 52. As fully described below,
backplate damper 52 is seated on a front face 54 of the buffer 46,
and backplate damper 52 serves to engage the recoiling bolt 36 for
establishing its recoil position (FIG. 2). A coil compression
action spring 56 is provided guidance and support on the guide rod
38 and normally maintains the backplate damper 52 bottomed against
the buffer face 54 while urging the bolt 36 into its battery
position in engagement with the rear face 34 of the conversion
chamber adaptor 22.
A longstanding problem encountered in firearm bolts such as the one
illustrated in this embodiment concerns the desirability to provide
a relatively large fillet radius at the juncture of the shank 58 of
the firing pin 60 (FIG. 2) and its enlarged rear flange or head 62
to minimize any sharp corners which may otherwise result in the
shank 58 being broken off from the flange 62 under repeated hammer
impact which imposes certain bending moments on the reduced
cross-sectional portion of the pin 60. Nonetheless, when the
juncture between the shank 58 and the flange 62 is formed with a
large fillet radius, end coils of the return spring 64 adjacent the
juncture tend to spread and bind up the pin 60 particularly between
the pin 60 and rear maximum diameter portion 66 of the firing pin
passageway 68. It will be understood that the forward limit of
firing pin movement is established by engagement of its rear flange
62 with shoulder 69 in the passageway 68.
To overcome these problems, the illustrated embodiment shows a
three-piece firing pin arrangement in FIG. 2 wherein the firing pin
60 is mounted directly in front of the striker 70 which is received
in maximum diameter portion 66 of the passageway 68 for limited
movement between forward and rear operative limit positions. The
forward and rear operative limit positions of striker 70 are
determined by engagement of the striker 70 with the firing pin 60
in its forward limit position and engagement of striker shoulder 74
with a fixed retaining pin 76 between shoulders 72, 74 of striker
70. Upon impact of hammer 78, after a full drop between opposed
vertical walls 80, 82 (FIG. 5) of rearwardly extending longitudinal
shoulders 84, 86 of the bolt 36, the pin 60 is driven forwardly
from its illustrated rear position to its forward position wherein
the tip of the pin 60 protrudes outwardly of a forward reduced
portion 68A of passageway 68 to detonate a primer of a chambered
cartridge and fire its bullet.
A relatively large fillet radius is desirably provided at the
juncture of firing pin shank 58 and flange 62, without the
undesired tendencies of the end coils of return spring 64 spreading
within the passageway 68, by virtue of a sleeve 90 fitted in
concentric relation about a rear portion of shank 58. Sleeve 90
presents an annular forwardly facing wall serving as a seat for an
end of return spring 64 which is thereby positively confined within
intermediate passageway portion 68B. The opposite end of return
spring 64 fits against a bevelled shoulder 92 within the bolt 36 at
a juncture between the intermediate passageway portion 68B and the
forward reduced portion 68A of passageway 68.
Upon firing, the reaction force of gases formed upon explosion of
the chambered round drive bolt 36 rearwardly. Automatic extraction
and ejection of empty cartridge cases such as at 94 in FIG. 4,
through an ejection port, not shown, is effected by a simplified
but significantly compact, rugged arrangement during rearward
recoil of bolt 36. An extractor member or claw 96 is pivotally
mounted in bolt 36 and urged inwardly toward its major longitudinal
axis X--X by an extractor spring 98 biasing a plunger 100 forwardly
against a heel of the claw 96, whereby during colt recoil, claw 96
rides down a ramp surface 102 within the conversion chamber adaptor
22 and engages a rim 104 of the spent cartridge case 94 to withdraw
it from the adaptor chamber 32.
During continued bolt recoil, the case 94 emerges from adaptor
chamber 32 and the base of the case 94 engages an ejection member
or lug 106 of magazine 108, whereupon an ejector assist member of
paw 110 throws the empty case 94 out the ejection port under the
force of its plunger spring 112 which is biased as best seen in
FIG. 4 in a manner similar to that shown in connection with the
claw 96. The pawl 110 protrudes forwardly of bolt face 114 and
provides a cartridge wall engaging portion 116 which is positioned
a discrete distance beyond the cartridge rim engaging portion 118
of the claw 96 such that, during recoil, the spring loaded pawl 110
rides down ramp surface 120 in the adaptor 22, engages the wall of
the spent case 94 and throws it out at a selected angle through the
ejection port when the cartridge base engages the cooperating
magazine ejection lug 106.
In this respect, the ejection lug 106 is located adjacent the path
movement of the pawl 110, and the pawl 110 is mounted in a
predetermined position relative to the extractor claw 96 and the
ejection port to ensure a proper angle of ejection. In the specific
illustrated embodiment, the pawl 110 is supported for pivotal
movement in a generally horizontal plane extending axially of the
bolt 36 with the path of pivotal movement of the extractor claw 96
lying in an axial plane extending at an angle of about 22
1/2.degree. to the horizontal to eject cartridge cases over the
extractor claw 96 and out the ejection port with an upward thrust
in the embodiment illustrated.
As the bolt 36 is driven back toward its recoil position, the
compression action spring 56 coiled about the guide rod 38 is
loaded, as spring 56 absorbs part of the recoil energy, and the
hammer 78 is returned to its illustrated cocked position upon being
engaged by an underlying shoulder 122 on the recoiling bolt 36.
When the bolt face 114 clears the magazine 108, which is suitably
modified to be installed within the magazine well 124 of lower
receiver 14 for storing and feeding rounds of a desired smaller
caliber, a magazine follower spring, not shown, feeds a live
cartridge into ready position (as seen in broken lines at 126 in
FIG. 2) to be picked up by the bolt 36 during its return forward
movement and to be chambered in the adaptor 22 for firing.
To minimize rebound and repeatedly absorb high impact loads
responsive to firing and to also effect a smooth counter recoil
movement to the bolt 36 under the bias of the compressed action
spring 56 with minimal bolt bounce at battery impact, the backplate
damper 52 is mounted on the guide rods 38, 40 at the rear of the
conversion assembly 10. This damper not only absorbs recoil impact
energy when the recoiling mass strikes the damper 52, but
additionally transmits that energy to the rifle buffer 46 and
effectively minimizes impact energy return to bolt 36. Accordingly,
in accordance with this invention, the damper 52 is seated against
the buffer 46 and is supported for limited movement on the guide
rods 38, 40 with the damper 52 normally urged forwardly a
predetermined distance from its rear limit position by the buffer
46 when bolt 36 is in battery. As best seen in FIG. 1, the extent
of damper movement is limited by a clearance gap between abutment
walls of rod receiving wells such as at 128 and the heads 50 of the
guide rods 38, 40 which establish a rear limit position for the
damper 52. It has been found that a clearance of, say, 0.080 to
0.100 inch provides satisfactory damping of the recoiling mass and
subsequent transmission of its energy to the rifle buffer 46 to
bring the bolt 36 to a substantially dead stop for a smooth return
motion under the bias of the loaded action spring 56. As the bolt
36 moves forwardly, its face 114 picks up a cartridge such as at
126 from the magazine 108 and chambers the round. The ejection lug
106 on magazine 108 will be seen to be received within a
longitudinally extending groove 130 on the bottom surface of the
bolt 36 (FIG. 3). As the bolt 36 moved home into battery position,
the claw 96 and ejector assist pawl 110 are biased radially
outwardly upon their engaging ramp surfaces 102 and 120 in adaptor
22 and the conversion assembly 10 is conditioned for firing the
next round.
In addition to serving as both a backplate and a damper, member 52
additionally has a lug receiving locating slot 132 which cooperates
with a buffer catch lug 134 in lower receiver 14 to maintain
conversion assembly 10 in operative position. A similar cooperating
slot and lug arrangement is provided at the forward end of the
assembly (FIG. 2) wherein a bottom surface of adaptor 22 has a
longitudinally extending slot 136 which receives an upstanding lug
138 at the front of the top wall of magazine 108 to additionally
restrain the installed conversion assembly 10 against undesired
angular movement relative to receiver 14. Moreover, hammer
movements additionally are of assistance should any minor
misalignment of bolt 36 relative to its guide rods 38, 40 occur,
for the longitudinally extending shoulders 84, 86 on the rear of
bolt 36 would then be engaged and cammed back into proper position
by hammer 78 during its movement between cocked and firing
positions.
A conversion assembly 10 of the type disclosed will be seen to be
quickly installed and easily removed from a firearm with which it
is being used. To remove the conversion assembly 10, the rifle 12
shown in the specifically illustrated embodiment need only be
opened, after the magazine 108 has been removed, and the conversion
assembly 10 is then rotated as a unit to disengage its adaptor lugs
24 from the breech end of barrel 28 whereupon the entire conversion
assembly 10 is detachable as an integral unit. Moreover, the
conversion assembly 10 of this invention may be economically
manufactured and, due to its simplified but rugged construction, is
particularly suited for extended use with minimum service
requirements.
As will be apparent to persons skilled in the art, various
modifications, adaptations and variations of the foregoing specific
disclosure can be made without departing from the teachings of the
present invention.
* * * * *