US3098311A - Bolt stop for semiautomatic firearm - Google Patents

Description

y 3, 1963 e. v. SAVIOLI BOLT STOP FOR SEMIAUTOMATIC FIREARM 3 Sheets-Sheet 1 Filed. Feb. 27, 1962 JNVENTOR. Giulia V Exuvinli BY J} $4M? .1 Pa

July 23, 1963 G. v. SAVIOLI 3,098,311

BOLT STOP FOR SEMIAUTOMATIC FIREARM Filed Feb. 27, 1962 3 Sheets-Sheet 2 Ill") 1 4 IN V EN TOR.

' EiuliuVSnvinli BY 1. 4. firtml 0. J. Q1?

July 23, 1963 s. v. SAVIOLI v3,093,311

BOLT STOP FOR SEMIAUTOMATIC FIREARM Filed Feb. 27, 1962 s Sheets-Sheet a FigiE- 74 IN V EN TOR.

Giulia V Euvi 01;: BY

BOLT STU? FGR SEIVHAUTOMATIC FIREARM Giulio V. Savioii, Westfield, Mass assignor to the United States of America as represented by the Secretary of the Army Filed Feb. 27, 1962, Ser. No. 176,164

(Ilaims. (ill. 42-18) (Granted under Title 35, US. Code (1952-), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to firearms with longitudinally reciprocal bolts and is more particularly directed to improved means for holding the bolt in the own or retracted position thereof.

In military firearms of the type wherein the ammunition therefor is vertically stacked in a removable box magazine from which each cartridge is successively fed into firing position by the forward stroke of a reciprocal bolt, it is frequently desirable to hold such bolt in the open position to which it is adapted to be recoiled or manually retracted after the last cartridge in the magazine has been fired. In the 7.62 mm. M14 Springfield rifle, for example, this holding function is currently accomplished by a stop which is pivotally mounted in the side of the receiver and is normally biased to lie beneath the longitudinal path of the bolt. As the last cartridge is stripped from the magazine, the corresponding rise of the cartridge follower therein is employed to pivot and hold such stop in engagement with the front face of the bolt. However, subsequent removal of the magazine from the rifle terminates this locking function of the magazine follower and the bolt stop is thereafter held in engagement with the bolt solely through the forward bias imparted thereto by the operating spring therefor.

However, extensive use of the rifle in the field has clearly demonstrated the necessity for improving this bolt holding arrangement to substantially reduce the ease with which the engagement between the bolt and the bolt stop may be nullified once the magazine has been withdrawn from the firearm for reloading or other purposes. It has been found that even a slight jar or impact to the rifle can cause the operating spring therein to surge rearwardly and reduce the forward bias thereof to such an extent that the bolt stop will be prematurely pivoted out of holding engagement with the bolt. Such accidental release of the open bolt will not only inconvenience the operator in his inspection or cleaning of the exposed parts of the rifle but may even result in physical injury if the release occurs while the fingers of the operator are in the path of travel of the bolt.

It is, therefore, an object of this invention to provide means for locking the bolt of a firearm, such as the M14 Springfield rifle, against inadvertent release from the open position thereof once the locking effect of the magazine follower has been Withdrawn.

It is a further object of this invention to provide an improved bolt holding means of the aforesaid type which Will be automatically locked in place upon the removal of the magazine from the rifle and automatically unlocked upon the reinsertion of the magazine for subsequent manual release by the operator.

It has also been found expedient in some instances to hold the bolt in the open position thereof prior to the release of the last cartridge in the magazine. While Patent No. 2,499,378 to John C. Garand teaches a bolt stop which is adapted to be actuated into bolt holding position independently of the presence or absence of the magazine in the firearm, such arrangement is inadequate from a military standpoint in that the firing of the last cartridge in the magazine does not automatinited States Patent 3,698,311 Patented July 23, 1963 "ice cally initiate the retention of the bolt in retracted position.

Accordingly, it is another object of the present invention to provide improved means for locking a longitudinally reciprocal firearm bolt in the open position at the option of the operator at any time prior to the withdrawal of the last cartridge from the magazine.

It is a specific object of this invention to provide a simple and reliable device for holding the bolt of the 7.62 mm. Springfield M14 rifle in the open position with equal positiveness in the presence or absence of a cartridge magazine.

These objects have been accomplished through the provision of a separate bolt lock pivotally mounted on the same pin employed for operation of the type of pivotal bolt stop normally employed in firearms of this kind. Suitable spring means are associated with this bolt lock in such manner as to automatically ensure positive locking of the bolt stop whenever the magazine is removed from the firearm at the time the bolt stop is holding the bolt in the open position. In addition, the bolt stop lock of the present invention also includes means for continuing the locking function thereof despite the subsequent reinsertion of a loaded magazine into the firearm. Each of the foregoing results is achieved without interfering with the essential military requirement that the bolt be automatically locked in the open or recoiled position upon the firing of the last cartridge in the magazine.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

'FIG. 1 is an elevational side view of the M14 Springfield rifle, partially in section, with the bolt in battery position and the bolt holding means of the present invention in the inoperative position thereof;

FIG. 2 is a fragmentary sectional view taken along line 22 in FIG. 1 to illustrate the relationship of the bolt stop and lock therefor in the inoperative position;

FIG. 3 is a full cross-sectional view taken along the same line as FIG. 2 but showing the bolt stop holding the bolt in the open position and being locked in place by the follower of the empty cartridge magazine;

FIG. 4 is a fragmentary sectional view taken along the same line as FIG. 2 but showing the bolt stop and the lock therefor in the operative position while the magazine is being withdrawn from or replaced in the firearm;

FIG. 5 is a cross-sectional view similar vto that of FIG. 3 but showing the bolt stop and the lock therefor in the operative position while the magazine is still in the firearm and prior to the complete emptying thereof; and

FIG. 6 is an exploded perspective view of the bolt stop assembly.

Although the structure and function of the present invention is here illustrated in connection with the 7.62 mm. Springfield M14 rifle, it should be understood that the principles demonstrated are equally applicable to any semiautomatic or automatic rifle in which a plurality of cartridges 12 are vertically stacked in a removable boxtype magazine 14'- suitably latched into the underside of a receiver 16. Cartridges 12 are arranged tobe successively chambered into a barrel 18 by a bolt 20 slidably mounted for reciprocal longitudinal movement in suitable ways 22 formed within receiver 16. In the firearm here illustrated, the face of bolt 2t) is provided with opposed outwardly projecting locking lugs 21 and is normally urged forwardly into battery position by an operating rod 24 slidably disposed in one side of receiver 16 and normally biased forwardly by an elongated spring 26.

The opposite side of receiver 16 is provided with a reverse L-shaped cutout section 28 which, as best shown in FIG. 6, is disposed adjacent the rearwardmost position of the face of bolt 2% and slightly below the longitudinal path of travel thereof. The forward and rearward ends of cutout section 28 are formed by outwardly proiecting ears or lugs 30 having axially aligned mounting holes 32 therethrough for a bolt stop pin 34. As illustrated in FIG. 6, pin 34 is preferably of the split type and slightly larger in diameter than that of mounting holes 32; to ensure adequate retention of the ends thereof in lugs 38.

A bolt stop 36 is provided with an axial hole 38 therethrough of sufiicient diameter to permit pivotal mounting thereof on pin 34. The inner end of stop 36 is formed with a projecting substantially rectangular portion 4% arranged to extend through cutout section 28 into the interior of receiver to. The outer end of stop 36 is provided with a depending tail portion 47. having a downwardly and outwardly inclined inner face 44 arranged, in the inoperative position thereof, to clear a substantially rectangular shelf at extending from the side of receiver 16 between lugs 36. The lower end of tail portion 42 terminates in an outwardly projecting step 43 while the upper end thereof extends above rectangular portion 40 for a purpose to be later shown. Bolt stop 36 is normally urged toward the inoperative position by a suitable spring contained within a hole 52 in the side of receiver shelf 46 and bearing against bolt stop inner face 44.

The underside of bolt stop portion 443 is notched, as shown at 54-, to receive a corner of the magazine follower 56 employed to raise cartridges 12 into position to be chambered by the forward movement of bolt 26 into battery position. The final upward movement of this magazine follower 56 is employed to pivot portion 49 of bolt stop 36 in front of the adjacent one of tie opposed locking lugs 21 on bolt 20 which was recoi-led to the open position thereof upon the firing of the last cartridge 12 in magazine 14. As long as magazine 14 is left in the firearm, follower 56 therein serves to positively hold bolt stop 36 in engagement with the forwardly biased bolt 29. However, once magazine 14 is removed from the firearm and the holding function of follower 56 is withdrawn, even a relatively light jar or impact on the firearm may be sufficient to cause enough surge in operating rod spring 26 to lower the pressure between bolt stop 36 and lug 21 on bolt 20 beyond the amount required to overcome the bias of bolt stop spring Stl. In such event, bolt stop 36 will be pivoted to release bolt 20 against the wish of the operator with resulting annoyance and even the possibility of injury.

Accordingly, a separate bolt stop lock 60 is pivoted on pin 34 in adjacent relation to bolt stop 36 for movement into and out of the vertical leg of cutout section 28 in receiver 16. The upper end of lock 60 is formed with a channel 62 opening toward receiver 16, and immediately below channel 62 there is provided a projecting shelf 64. The lower end of lock 6%) terminates in a hook portion 66 having an arcuate exterior periphery and disposed in vertical alignment with shelf 64- to form an open portion 67 therebetween. A torsion spring 68 having elongated ends 70 is seated in a suitable recess 72 formed into the top of shelf 64-. One end of spring 68 bears against the floor of channel 62 while the other end of spring 68 bears against the exterior surface of receiver 16 thereby normally urging hook 66 of lock ea in a clockwise direction into the interior of receiver 16.

When a magazine 14 which is fully or partially loaded with cartridges 12 is latched in the firearm, the side wall of such magazine will block the full locking movement of bolt stop lock 69 as best shown in FIG. 5. Accordingly, the side of bolt stop 35 adjacent lock 69 is provided with a spring-biased plunger 74 arranged to be retained in place by any simple expedient, such as a hole 76 whose edges are peened to reduce the size of the opening below the diameter of plunger 7 If a more positive retention is The outer end of plunger 74 is pref- 4 erably formed with a conical taper 82 to ensure positive operation thereof. When bolt stop 36 is pivoted to raise stop portion 49 thereon in front of bolt lug 21, end 82 of plunger 74 is positioned to be engaged by the front face of bolt stop lock 60 whereby the greater bias imparted to bolt stop lock 6% by torsion spring 68 overcomes the bias of spring 50 to hold bolt stop 36 against inadvertent disengagement from bolt lug 21. However, when bolt stop 36 is manually pivoted out of engagement with bolt lug 21, tapered end 82 of plunger 74 rides over the corner formed by the front and side surfaces of bolt stop lock 60 and is, consequently, forced back into hole 76.

As previously explained, retention of bolt 2% in the open position shown in FIG. 3 is automatically accomplished upon the firing of the last cartridge in magazine 14 by the final upward movement of the magazine follower 56. Upon subsequent removal of the empty magazine 14 from the rifle, torsion spring 68 automatically pivots bolt stop lock 60 inwardly of receiver 16 to bring shelf 64 into contact with the underside of bolt stop portion 4% and thereby hold bolt stop 36 in the operative position, as shown in FIG. 4, despite any variation in the forward thrust of bolt 20. Although bolt stop spring 50 urges stop 36 in a counterclockwise direction, such result is of course, completely nullified by the greater clockwise rotation imparted to bolt stop lock 6!) by spring 68.

When magazine 14 is replaced in the rifle in either a loaded or empty condition, the outer corner thereof will strike the arcuate periphery of hook 66 and force bolt stop lock 60 in a counterclockwise direction. Although this movement of bolt stop lock 60 removes the particular locking support given to bolt stop 36 by shelf 64, the required locking of bolt stop 36 will not be completely withdrawn as has been the case in similar bolt stops of prior art construction. Instead, the counterclockwise movemcnt of bolt stop lock 60 uncovers plunger 74 which moves outwardly of hole 76 to the extent permitted b retaining pin 86). Thus, the locking function of bolt stop lock 66 is continued through the engagement thereof with plunger 74 instead of being directly imparted thereto by the contact of shelf 64 against bolt step portion 40.

In the event the operator of the rifle should find it necessary to release bolt 20 for return to the locked battery position thereof, this may be readily accomplished merely by exerting sufiicient manual force on the projecting upper end of bolt stop 36 to pivot stop portion 40 out of engagement with bolt lug 21 as shown in FIG. 2. Subsequent locking of bolt 20 in the open position can be accomplished with equal facility merely by retracting bolt 20 and applying the required manual force against the protruding step 43 on bolt stop 36 to pivot the latter to the operative position shown in FIG. 3.

Accordingly, the present invention provides an improved bolt stop mechanism which oan be readily locked to retain the bolt in the open position and can be as readily unlocked to release the bolt for movement into battery position. Furthermore, the means for locking the bolt stop is specifically designed to accomplish this f LlBCtlOn in automatic response to the insertion and withdrawal of the magazine from the firearm. What is more important, the aforementioned locking and unlocking operation of the bolt stop can be carried out without the necessity of tampering with or eliminating such essential military requirements as the automatic retention of the bolt in open position upon the firing of the last cartridge in the magazine and the necessity for manual actuation of the bolt stop at the option of the operator of the rifle without any removal of the magazine therefrom.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the following claims are intended to include such variations.

I claim:

1. In a firearm having a slidable bolt disposed for longitudinal reciprocation between battery and recoil positions, a releasable magazine for holding a vertical stack of cartridges, and a spring-biased follower in the magazine for successively lifting the uppermost cartridge in the stack into the path of the bolt upon movement thereof into recoil position, the improvement of means for retaining the bolt in the recoil position independently of the magazine comprising in combination, a bolt stop pivoted below the longitudinal path of the bolt and adjacent the recoil position thereof, spring means normally urging said stop in a counterclockwise direction away from engagement with the bolt, a lock pivotally mounted in adjacent coaxial relation with said bolt stop, spring means normally urging said lock in a clockwise direction into supporting engagement with said bolt stop for locking the bolt in the recoil position thereof in the absence of the magazine in the firearm, and means for transferring the pivotal movement of said lock to said bolt stop following the withdrawal of the supporting engagement therebe tween upon the rein'sertion of the magazine into the firearm.

2. In a firearm having a receiver, a bolt slidably disposed therein for longitudinal reciprocation between battery and recoil positions, a magazine releasably latched in the underside of the receiver for holding a vertical stack of cartridges, a spring-biased follower in the magazine for successively lifting reach cartridge in front of the bolt, and a stop pivotally mounted in the side of the receiver to lie in the path of the magazine follower for actuation thereby into the path of the bolt toward battery position upon the removal of the last cartridge from the magazine, the improvement of a lock pivotally mounted in adjacent coaxial alignment with the bolt stop, a spring normally urging said lock into the interior of the receiver into supporting engagement with the bolt stop, in the absence of the magazine in the receiver, to substitute for the locking function previously afforded by the magazine follower, and a compressible plunger slidably disposed in the side of the bolt stop for engagement with the front of said lock at the conclusion of the pivotal movement imparted thereto by the reinsertion of the magazine in the receiver whereby said plunger transfers the bias of said bolt stop lock spring to the bolt stop to continue the retention of the bolt in the recoil position thereof.

3. The combination defined in claim 2 wherein the upper and lower ends of the bolt stop extend beyond the periphery of said bolt stop lock to permit manual actuation of said stop into and out of engagement with the bolt independently of the magazine.

4. In a firearm having a receiver, a bolt slidably disposed therein for longitudinal reciprocation between battery and recoil positions, a magazine releasably latched in the underside of the receiver for holding a vertical stack of cartridges, and a spring-biased follower in the magazine for successively lifting each cartridge into the path of the bolt toward battery position, the improvement of means for locking the bolt in the recoil position comprising, in combination, a stop pivotally mounted in the side of the receiver with a stop portion extending into the interior thereof to lie in the path of the magazine follower for actuation thereby into the path of the bolt upon the removal of the last cartridge from the magazine, a lock pivotally mounted in the side of the receiver in adjacent coaxial alignment with said bolt stop, said lock having a projecting shelf extending into the receiver to lie beneath the projecting stop portion on said bolt stop, first spring means disposed between said bolt stop and the receiver for pivoting said bolt stop portion away from engagement with the bolt, second spring means disposed between said bolt stop lock and the receiver and of greater bias than said first spring means for pivoting said bolt stop lock into contact with the side of the magazine and into supporting engagement with said bolt stop portion in the absence of the magazine in the receiver, and a compressible plunger slidably retained in the side of the bolt stop adjacent said bolt lock, said plunger being positioned to engage the front of said bolt stop lock during the con tact between said lock and the side of the magazine whereby the greater bias of said bolt stop lock is transferred to said bolt stop to retain the latter in engagement with the bolt.

5. The combination defined in claim 4 wherein said bolt stop extends upwardly beyond said shelf thereon to provide a lever for manual release of the bolt from the recoil position thereof while the magazine remains in the firearm and wherein said bolt stop is formed with an outwardly projecting step adapted to protrude beyond the rear end of said bolt stop lock prior to removal of the magazine from the firearm and thereby permit the manual actuation of said bolt stop into engagement with the bolt in the recoil position thereof.

6. The combination defined in claim 4 wherein said compressible plunger is formed with an annular retaining notch and wherein a retaining pin of lesser width than said notch is transversely mounted in said bolt stop for engagement in said retaining notch to prevent ejection of said plunger from said bolt stop when said bolt stop lock is pivoted outwardly to expose said plunger during the reinsertion of the magazine into the firearm.

References Cited in the file of this patent UNITED STATES PATENTS 944,606 Frommer Dec. 28, 1909 FOREIGN PATENTS 215,425 Switzerland Sept. 16, 1941

Claims (1)

1. IN A FIREARM HAVING A SLIDABLE BOLT DISPOSED FOR LONGITUDINAL RECIPROCATION BETWEEN BATTERY AND RECOIL POSITIONS, A RELEASABLE MAGAZINE FOR HOLDING A VERTICAL STACK OF CARTRIDGES, AND A SPRING-BIASED FOLLOWER IN THE MAGAZINE FOR SUCCESSIVELY LIFTING THE UPPERMOST CARTRIDGE IN THE STACJ INTO THE PATH OF THE BOLT UPON MOVEMENT THEREOF INTO RECOIL POSITION, THE IMPROVEMENT OF MEANS FOR RETRAINING THE BOLT IN THE RECOIL POSITION INDEPENDENTLY OF THE MAGAZINE COMPRISING IN COMBINATION, A BOLT STOP PIVOTED BELOW THE LONGITUDINAL PATH OF THE BOLT AND ADJACENT THE RECOIL POSITION THEREOF, SPRING MEAND NORMALLY URGING SAID STOP IN A COUNTERCLOCKWISE DIRECTION AWAY FROM ENGAGEMENT WITH THE BOLT, A LOCK PIVOTALLY MOUNTED IN ADJACENT COAXIAL RELATION WITH SAID BOLT STOP, SPRING MEANS NORMALLY URGING ENGAGEMENT WITH SAID BOLT STOP FOR LOCKING THE PORTING ENGAGEMENT WITH SAID STOP FOR LOCKING THE BOLT IN THE RECOIL POSITION THEREOF IN THE ABSENCE OF THE MAGAZINE IN THE FIREARM, AND MEANS FOR TRANSFERRING THE PIVOTAL MOVEMENT OF SAID LOCK TO SAID BOLT STOP FOLLOWING THE WITHDRAWAL OF THE SUPPORTING ENGAGEMENT THEREBETWEEN UPON THE REINSERTION OF THE MAGAZINE INTO THE FIREARM.

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