US3426465A

US3426465A - Firearm with non-binding manual bolt action

Info

Publication number: US3426465A
Application number: US650816A
Authority: US
Inventors: Thomas R Robinson Jr
Original assignee: Marlin Firearms Co
Current assignee: Marlin Firearms Co
Priority date: 1967-07-03
Filing date: 1967-07-03
Publication date: 1969-02-11
Anticipated expiration: 1986-02-11

Description

1969 1-. R. ROBINSON, JR 3,426,465

FIREARM WITH NON-BINDING MANUAL BOLT ACTION Filed July 5, 1967 Sheet of 2 g Z 1 2 v N i T. R. ROBINSON, JR

Feb. 11', 19,69

' 'FIREARM wnn NON-BINDING MANUAL sow ACTION Sheet g 0T2 Filed July 3. 1967 BY &

12 Claims ABSTRACT OF THE DISCLOSURE The disclosure deals with a breech bolt having with its cylindrical body and conventional front locking lugs the usual relatively loose fit in the receiver bore and side channels therein for its excursions into open and closed position, with the closed bolt being turnable into and from firm interlock with the receiver in usual manner. Featured is a longitudinal groove in the bolt and a key in the rear part of the receiver, of which the key has on the bolt excursions into open and closed position a sufficiently close sliding fit in the groove at least to prevent such canting of the bolt in the receiver as would cause binding of the former in the latter especially on opening the bolt, with the groove and key being otherwise arranged to permit turning of the closed bolt into and from interlock 'with the receiver.

This invention relates to bolt-action firearms in general, and to firearms with manually operated breech bolts in particular.

While the relatively loose fit of the breech bolt in the receiver on its opening and closing excursions makes for ease or bolt manipulation and other advantages, it also gives rise to objectionable binding of the bolt in the receiver especially on attempting rapid reloading of the firearm. The cause of such binding is almost invariably an attempt by the operator of the firearm rapidly to retract the bolt to its open position while he continues to exert on the bolt most, if not all, of the turning force which unlocked the bolt. Such action is entirely spontaneous by any operator attempting quick bolt opening. What happens under these circumstances is that the moment the bolt leaves on its rearward excursion the full-ring front confines of the receiver and enters the region of the ejector port therein, and also a cartridge injector port if provided therein, the continued turning force on the bolt will cant the latter, with its left front lug formation bearing against the lower wall of the side channel in the receiver in which it passes, and with its cylindrical body bearing against the top of the full-ring rear confines of the receiver, with the result that a long-arm and, hence powerful, couple on the bolt holds the latter with wedge-like resistance to further retraction. To avoid such binding, recourse has been had in the past to different devices with generally good results, but these devices have entailed rather high, and in some cases prohibitive, cost.

It is the primary aim and object of the present invention to provide in a firearm of this type a device which not only obviates binding of the breech bolt on any manipulation thereof, including its aforementioned quick opening, but which is also of exceedingly low cost, and in any event of much lower cost than any of the prior devices.

It is another object of the present invention to provide in a firearm of this type the aforementioned device which neither ordinarily interferes with, nor requires any particular coordination with any of the bolt and receiver formations that provide for, the usual relatively loose fit of the bolt in the receiver for its excursions into open and closed position, and which acts, independently and only on such bolt manipulation that would ordinarily be connited States Patent ductive to binding in the receiver to tighten the fit of the bolt in the receiver only to the extent of preventing canting of the same into the binding tightness with the receiver.

It is a further object of the present invention to provide in a firearm of this type the aforementioned independent device in the structurally simple form of a longitudinally groove in the bolt and a key in the receiver, of which the key is provided in the receiver significantly in the fullring rear confines thereof, and has on the bolt excursions into open and closed position with the groove a sliding fit which may be fair but is closer than that of the bolt in the receiver, with the groove and key being otherwise arranged to permit turning of the closed bolt into and from its locked position. With this arrangement, one side of the groove will, on binding-conductive bolt manipulation, ride firmly on the key, with the groove and key than cooperating to take up at least that bolt play in the receiver which would otherwise permit the bolt to respond to such manipulation in canting into binding tightness with the receiver. Therefore, the only resistance to bolt excursion under these conditions is simple sliding friction of the bolt in the receiver which, moreover, is largely confined to the axially short region of the full-ring rear confines of the receiver and, hence, has no binding effect on the bolt under the worst conditions. Also, while it is apparent that the groove and key require no particular coordination with any of the bolt and receiver formations that provide for the usual relatively loose fit of the bolt in the receiver, such general coordination of the bolt and receiver with the groove and key as is required to bring about the abovementioned relative fit conditions, is obtained quite easily and within readily maintained tolerances. In this connection, it is even in mass production of the bolts and receivers a simple matter to keep the machining of the groove in the bolt and the location of the key in the receiver within easily maintained tolerances at which the grooves and keys will, in subsequent action of the bolts and receivers, take up binding-conductive play of the bolts in the receivers. Still further, with the present device taking over actual control over the angular position of the locking lugs on the bolt on the latters excursions, the side channels in the receiver through which these lugs pass need not be guide channels, but may be mere clearance channels, for these lugs and hence, may be made still wider than usual with ensuing still greater facility to arrange the grooves and keys in mass production of the bolts and receivers at the aforementioned general coordination with the latter.

Another object of the present invention is to provide in a firearm of this type the aforementioned groove and associated key in the breech bolt and receiver, of which the key is received in a radial slot in the receiver and normally spring-urged into the bolt groove, and this groove is at some distance from the forward end of the bolt run out to the periphery of the latter to cam the key into its slot sufficiently to clear the bolt for withdrawal from the receiver on first rectracting the usual bolt stop to this end. With this arrangement, the groove is terminated short of the forward end of the bolt and, hence, affords no rearward leakage path for powder gases, and the key requires no manipulation to clear the belt for withdrawal of the latter from the receiver.

A further object of the present invention is to provide in a firearm of this type the aforementioned groove and associated spring-urged key in the breech bolt and receiver, of which the key has also a cam formation for its depression into its slot by the forward end of the bolt on reentry of the latter into the receiver, whereby the key also clears the reentering bolt Without requiring any manipulation.

Further objects and advantages will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

FIG. 1 is a fragmentary longitudinal sectional view, partly in elevation, of a firearm embodying the present invention;

FIG. 2 is a fragmentary section through the firearm taken substantially on the line 22 of FIG. 1;

FIG. 3 is a section similar to FIG. 2, but showing a prominent operating part of the firearm in a different position;

FIG. 4 is a fragmentary section through the firearm taken substantially on the line 44 of FIG. 3;

FIG. 5 is a fragmentary section through the firearm taken substantially on the line 55 of FIG. 3;

FIG. 6 is a fragment longitudinal section through the firearm taken substantially on the line 6-6 of FIG. 5;

FIG. 7 is a fragmentary section through the firearm taken substantially on the line 77 of FIG. 1; and

FIG. 8 is a fragmentary section similar to FIG. 7 and showing a modified form of the invention.

Referring to the drawings, and more particularly to FIGS. 1 to 5 thereof, the reference numeral 10 designates a firearm having as its principal components a barrel 12, a stock 14 with a removable box magazine 16, a receiver 18 and a breech bolt 26.

The receiver 18, which at 22 is mounted on the stock 14 and at 24 is connected with the barrel 12 in usual manner, has a longitudinal bore 26 with conventional opposite front locking grooves 28 and

opposite side channels

30 and 32, as well as a cartridge ejector port 34 and in this instance also a cartridge injector port 36 in line with the box magazine 16. The receiver 18 further has a bottom slot 38 (FIGS. 1 and 5) into which extends a mounting bracket 40 for parts, including a pivoted sear 42, a scar spring 44 and a trigger 46, with the bracket 40 being received in an aperture 48 in the stock 14 and suitably mounted in the latter.

The breech bolt 20, which is operationally slidable and turnable in the receiver 18, is provided with a rear operating handle 50 and with conventional opposite front locking lugs'52 and 54. Provided on and in the bolt is a conventional firing unit 56 comprising a firing pin 58 and a main spring 60 therefor (FIG. 5), a cocking piece 62 (FIG. 1) which is connected with the firing pin, and a bolt sleeve 64 threadedly received in the bolt 20 and having the usual rear knob 66. The firing unit 56 is, as such, axially slidable with the bolt 20 into its open and closed positions, but is, by register of the cocking piece 62 in a guide groove 68 in the receiver 18 held against rotation with the closed bolt 20 into and from its locked position (FIG. 1).

FIG. 1 shows the firearm ready for firing. Thus the bolt 20 is in its closed position locked to the receiver 18 by virtue of interlock of the bolt lugs 52, 54 with the locking grooves 28 in the receiver, and the piece 62 and therewith connected firing pin 58 are held in cocked condition by the sear 42. Therefore, on pulling the trigger 46, the cocking piece 62 will, under the force of the main spring 60, cam the sear 42 out of the way against the weaker sear spring 44, and the main spring 60 will project the firing pin 58 into forward firing position in which to fire the chambered cartridge c. After firing this cartridge, the bolt 20 is at its handle 50 turned from its locked position, anticlockwise as viewed in the direction of the arrow 70 in FIG. 2, into its unlocked, but still closed, position, in the course of which the bolt lugs 52, 54 are moved out of the locking grooves 28 and into the front part of the respective side channels and 32 in the receiver 18, and the piece 62 with the firing pin is cocked on cooperation between a cam formation 72 on the thus turning bolt 20 and a follower shoulder 74 on the non-turning piece 62. The bolt 20 is thereupon retracted from its unlocked closed position to its fully open position in which the bolt lugs 52 bear against a bolt stop 78 to prevent further retraction of the bolt in the receiver. During such excursion of the bolt from closed to fully open position, an extractor and ejector (neither shown) on the bolt will retract the fired cartridge shell 0 from the firing chamber 72 and eject it through the port 34, and the topmost cartridge 0 in the magazine 16 will by the usual cartridge follower (not shown) be lifted in the injector port 36 into position to be chambered by the bolt on its following excursion from open into closed position. After next closing the bolt 20 and, in consequence, chambering the next cartridge c and bringing the cocked piece 62 to bear against the sear nose 80 (FIG. 1), the bolt 20 is at its handle 50 turned, clockwise as viewed in the direction of the arrow 70 in FIG. 2, into its locked position, in the course of which the bolt lugs 52 and 54 leave their

channels

30 and 32 and move into interlock with the grooves 28 in the receiver, and the cam formation 72 on the bolt moves out of operative relation with the follower shoulder 74 on the cocking piece 62 (FIG. 2). The firearm is now ready for firing the chambered cartridge on pulling the trigger 46. The explained cycle of extracting and ejecting the fired cartridge shell and chambering the next cartridge from the magazine is repeated on unlocking the bolt 20, retracting the same from its closed unlocked position to its fully open position, then returning the same to its closed position and finally locking the same in its closed position, as well be readily understood.

The breech bolt 20 with its front locking lugs 52, 54 has the customary relatively loose fit in the receiver bore 26 and

side channels

30, 32 therein. While this is of advantage in that it makes for ease of manipulation of the bolt on its excursions into open and closed position, and further makes for low cost of the receiver and bolt owing to relatively widely permissible tolerances in their machining, it also entails on occasion more or less severe binding of the bolt in the receiver, especially when the operator of the firearm attempts rapid reloading of the same, with ensuing annoyance, if not dire consequences, to the operator. Thus, in attempting rapid reloading of a firearm, it is virtually spontaneous for any operator to unlock the bolt with considerable force and maintain most, if not all, of this turning force on the bolt while suddenly adding to this turning force a powerful axial force for bolt retraction. While these combined forces on the bolt have little tendency to cause binding of the latter in the receiver on its initial rearward excursion through the full-ring confines of the receiver bore 26 immediately in front of the ejector port 34, these forces will exert themselves to the fullest in tending to cause binding of the bolt in the receiver with optimum effect the moment the bolt leaves on its continued rearward excursion the full-ring confines of the receiver bore and enters the foremost region of the latter where interrupted by the ejector port 34, i.e., when the bolt reaches on its rearward excursion a position in the receiver like or similar to that shown in FIG. 3. Keeping in mind that the bolt 20 with its front lugs has in the receiver a relatively loose fit to the extent of having some rotational and also lateral play in the receiver bore 26 and

side channels

32 and 34 therein, the bolt will nevertheless not bind in the receiver on the exertion of any, and even on exceptionally large, turning force on the bolt while the same is retracted within the frontal circumferentially closed confines of the receiver bore, for therewithin the applied turning force on the bolt will cause the front lugs 52 and 54 to bear with equal and opposed forces against the bottom wall 82 and top wall 84 of the respective side channels 30 and 32 (FIG. 4) and thus preclude binding of the bolt in the receiver. However, when the bolt reaches on its rearward excursion a position like or similar to that shown in FIGS. 3 and 4 in which part of the side channel 32, including its top wall 84 is missing owing to the provision of the ejector port 34 thereat, the applied anticlockwise turning force on the bolt (FIG. 4) will cant the bolt in the receiver to the maximum extent permissible by the play of the former in the latter, with the left bolt lugs 52 then bearing with a force F1 against the bottom wall 82 of the side channel 30 and the bolt further bearing with an equal but opposed force F2 against the upper part of the rear end of the receiver bore (FIG. 5). These opposed forces form a couple of considerable moment in any event owing to the long arm a of the couple (FIG. 3), with this couple being particularly apt to cause binding of the bolt in the receiver on maintaining even a moderate turning force on the bolt on its retraction, and to cause binding of the bolt in the receiver with wedge-like resistance to further bolt retraction on maintaining on the bolt a greater turning force such as that usually maintained on rapid bolt opening attempts. Thus, on rapid bolt opening attempts with spontaneous maintenance of the bolt-unlocking force or torque on the bolt on its attempted quick retraction from closed to open position, binding of the bolt in the receiver will usually occur in a bolt position like or similar to that shown in FIG. 3, but bolt-binding in the receiver may occur at any stage of the bolts rearward excursion beyond the position in FIG. 3, though at decreasing binding tightness the more the bolt approaches its open position.

Featured in the firearm is a device which is designed to obviate binding of the breech bolt 20 in the receiver 18 on any manipulation, including quick opening, of the bolt without, however, requiring any closer than the customary relatively loose fit of the bolt in the receiver. This device is in the exceedingly simple form of a key 90 in the receiver 18 and an associated longitudinal groove formation 92 in the breech bolt 20 (FIGS. 5 and 6). Preferably and advantageously, the key 90 is provided in the circumferentially closed confines of the receiver bore 26 rearwardly of the ejector port 34 and in this instance also rearwardly of the injector port 36 in the receiver, and the groove 92 in the bolt 20 is preferably of suflicient longitudinal extent to register with the key 90 throughout the bolts excursions into open and closed position. While the key 90 need have but a fair fit in the groove 92 at easily maintained tolerances, its fit therein must be closer than the customary relatively loose fit of the bolt in the receiver. Preferably also, the groove 92 and key 90 are rectangular in cross-section and have median planes radially of the bolt 20 and receiver bore 26, respectively. Further, while the key 90 may be fixed in the receiver 18 and the groove 92 continued to the front end of the bolt 20 to permit rearward retraction of the latter from the receiver, the key 90 is preferably and advantageously yieldingly depressible in the receiver from the confines of the bore 26 therein. To this end, the key 90 is mounted for movement into and from the receiver bore 26 in a recess 94 in the receiver which preferably is a readily milled through-slot from the outer periphery to the bore 26 in the receiver (FIGS. 5 and 6), and this key is normally urged into the receiver bore 26 and into the bolt groove 92 by a spring 96. The key 90 is in this instance pivoted at 98 in the slot 94, and the spring 96 is received in a bored recess 100 in the slot 94 and interposed between a crosspin 102 in the slot and a socket-like depression 104 in the key (FIG. 6). With the key 90 being thus depressible from the confines of the receiver bore 26, the groove 92 in the bolt 20 need not extend to the front end of the latter, but is advantageously run out in front to the cylindrical periphery of the bolt in cam-like fashion like or similarly as indicated at 106. In thus terminating the groove 92 short of the front end 0 fthe bolt 20, the groove affords no rearward leakage path for powder gases, yet in no wise interferes with removal of the bolt from the receiver in the course of which the groove-end 106 simply cams the key from the groove and the key rides on the cylindrical periphery of the bolt to the front end of the latter. The bolt 20 may thus be removed from the receiver 18 on first retracting the bolt stop 78 from the path of the bolt lugs 52 by depressing a finger piece 108 on the receiver (FIGS. 2 and 3). On removal of the bolt from the receiver, the key will be spring-urged into the receiver bore 26 somewhat deeper than when riding in the bolt groove 92, and held against further inward motion by the edge 110 of the slot 94 (FIG. 6), and the key has a preferred cam-like formation 112 which cooperates with the front end of the bolt in depressing the key from the confines of the receiver bore 26 on reentering the bolt into the latter. Thus, the key 90 requires no manipulation for the removal of the bolt from, and its reentry into, the receiver.

With the key 90 being in register with the groove 92 throughout excursions of the bolt into open and closed position in the receiver, provision is made in the bolt for clearing the key 90 when on turning the closed bolt into and from its locked position the bolt groove 92 turns relative to the key 90. To this end, the groove 92 has at or near its rear end a lateral branch 114 which is preferably run out to the cylindrical bolt periphery in cam-like fashion like or similarly as indicated at 116 in FIG. 7, so that the key 90 is cammed onto the periphery of the bolt on turning the latter into its locked position (FIG. 1), and the key will reenter the groove 92 on turning the closed bolt from its locked position into its release position for retraction (FIG. 3). The key-receiving slot 94 in the receiver 18 is preferably angularly spaced from the ejector port 34 and from the

side channels

30 and 32 so that the bolt groove 92 is out of communication with this port and side channels on the bolt excursions into open and closed position and on turning the bolt into and from its locked position, so that no dirt or other foreign matter has ready access to the bolt groove 92 (FIGS. 5 and 7).

As an alternative to running the lateral groove branch 114 in the bolt 20 out to the cylindrical bolt periphery (FIG. 7), the lateral branch 114a of the groove 92a in the bolt 20a (FIG. 8) may be of the same depth as the groove 92a and extend peripherally of the bolt sufficiently to clear the key 900: when the bolt is in its locked position.

It is the principal designated function of the key and groove connection 90, 92 between the receiver 18 and breech bolt 20 to assume control over the angular position of the locking lugs on the bolt on the latters excursions into open and closed position at least to such an extent as to obviate canting of the bolt into the aforementioned binding tightness with the receiver on any manipulation, including quick and forceful opening, of the bolt. To achieve this, the key 90 has a fit in the bolt groove 92 which may be fair but must be closer than that of the bolt in the receiver, as already mentioned. Further, the coordination between the key 90 and bolt groove 92 on the one hand, and between the bolt lugs 52, 54 and the

respective side channels

30 and 32 in the receiver on the other hand, must be such that the key 90 and bolt groove 92 may perform their control over the angular bolt lug positions in the receiver to the abovementioned extent without interference from the

side channels

30, 32 in the receiver. Such coordination is readily achieved even in mass production of breech bolts and receivers on machining the grooves 92 in the bolts and the keyreceiving slots 94 in the receivers relative to the lugs 52, 54 on the bolts and the

side channels

30, 32 in the receivers within tolerances that need not be overly close and are easily maintained, so that on random assembly of mass-produced bolts with mass-produced receivers nonbinding performance of the bolts in the receivers is assured on any manipulation of the bolts. Indeed, since the key 90 and bolt groove 92 are to assume control, over the angular position of the bolt lugs in the side channels in the receiver, this is achieved with particular facility if the side channels are kept at greater width than usual with respect to the width of the bolt lugs, and this is entirely feasible since these side channels are not at all guide channels, but are mere clearance channels, for the bolt lugs.

With the key 90 and bolt groove 92 on the one hand, and the bolt lugs 52, 54 and

side channels

30, 32 in the receiver on the other hand, coordinated as described, the one side 120 of the groove 92 Will, on binding-conductive manipulation, and espectially quick-opening, of the bolt, ride firmly on the key 90 (FIG. with the groove and key then cooperating to take up at least that bolt play in the receiver which would otherwise permit the bolt to respond to such manipulation in appreciable canting in the receiver. Therefore, the only resistance to bolt excursion under these conditions is simple sliding friction of the bolt in the receiver which, moreover, is largely confined to the axially short region of the circumferentially closed confines of the receiver bore behind the ejector port 34 and, hence, has no appreciable binding effect on the bolt under the worst conditions.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

What is claimed is:

1. In a firearm, the combination with a receiver having a bore with open front and rear ends, opposite longitudinal channels with side walls, and opposite front locking grooves, in said bore of which said grooves extend between and lead to said channels, and an ejector port interrupting part of one of said channels including one side wall thereof over an intermediate length of said one channel; and a cylindrical breech bolt having outwardly projecting front locking lugs and a rear handle with which to slide said bolt in said receiver bore into open and closed positions and in said closed position turn said bolt into and from locked position in which said lugs and grooves are interlocked, with said lugs passing in said channels on bolt excursions int-o said open and closed positions, of a key in said receiver projecting into said bore thereof between said open rear end and ejector port; and a longitudinal groove formation in said bolt into which said key projects on said bolt excursions, with said key having in said groove formation a closer fit than said lugs in said channels to restrain said bolt on torque exertion thereon from moving with said lugs into binding tightness with any of said channel side walls, and said groove formation having a lateral branch to provide clearance for said key on turning said bolt into and from said locked position.

2. The combination in a firearm as in claim 1, in which said key projects radially into said receiver bore, and said groove formation has a median plane radially of said bolt.

3. The combination in a firearm as in claim 1, in which said key and groove formation are rectangular in crosssection.

4. The combination in a firearm as in claim 1, in which said receiver has in said bore a recess in which said key is received for movement into and from said bore and is spring-urged into said groove formation in said bolt, said bolt has a forward end, and an end length of said groove formation nearest said forward end runs in inclined cam fashion out to the cylindrical bolt periphery at a distance rearwardly from said forward bolt end so as to cam said key from said groove formation in said bolt on retraction of the latter from said receiver.

5. The combination in a firearm as in claim 4, in which said key has a cam portion cooperating with said forward bolt end in camming said key from said receiver bore on reentry of said bolt into said receiver.

6. The combination in a firearm as in claim 4, in which said key is pivotally mounted in said recess.

7. The combination in a firearm as in claim 4, in which said recess in said receiver is a slot therein leading from the outer periphery of said receiver to said bore therein.

'8. The combination in a firearm as in claim 1, in which said receiver has in said bore a recess in which said key is received for movement into and from said bore and is spring-urged into said groove formation in said bolt, and said lateral branch of said groove formation runs from the latter in inclined cam fashion out to the cylindrical bolt periphery so as to cam said key from said receiver bore on turning said bolt into said locked position.

9. The combination in a firearm as in claim 8, in which said bolt has a forward end, and an end length of said groove formation nearest said forward end runs in inclined cam fashion out to the cylindrical bolt periphery at a distance rearwardly from said forward bolt end so as to cam said key from said groove formation in said bolt on retraction of the latter from said receiver.

10. The combination in a firearm as in claim 9, in which said key has a cam portion cooperating with said forward bolt end in camming said key from said receiver bore on reentry of said bolt into said receiver.

11. The combination in a firearm as in claim 1, in which said key in said receiver is angularly spaced from said ejector port therein.

12. The combination in a firearm as in claim 1, in which said key in said receiver is angularly spaced from said ejector port and channels therein so that said groove formation in said bolt is out of communication with said port and channels on said bolt excursions and on turning said bolt into and from said locked position.

References Cited UNITED STATES PATENTS 1,161,172 11/1915 Von Frommer 42-16 SAMUEL FEINBERG, Primary Examiner.