US2570772A - Recoil operated firearm with pivoted bolt lock - Google Patents

Description

Oct. 9, 1951 R. cRlTTENDoN RECOIL OPERATED FIREARM WITH PIVOTED BOLT LOCK 5 Sheets-Sheet l Filed March 3, 1949 'JNVENTORQ LEX/5 RAY CHUTE/mom www ATTORNEYS Oct. 9, 1951 1 R. cRlTTENDoN RECOIL OPERATED F'IREARM WITH PIVOTED BOLT LOCK' 5 Sheets-Sheet 2 l Filed March 5, 1949 illy. 11.14 1

' INVENToR. LEX/E RAY CR/rrf/Voo/v ATTORNEYS Oct. 9, 1951 1 R. CRITTENDON REcoIL OPERATED FIREARM WITH PIvoTED BOLT Loox 3 SheetS-Sheet 5 Filed March 3, 1949 All" h..

F 7 Y l INVENToR. LEX/E RAV CR/rEA/o o/V ATTORNEYS Patented Oct. 9, 1951 RECOIL OPERATED FIR-EARM WITH PIV OTED BQLT LOCK Lexie Ray Crittendon, Ilion, N. Y., assigner to Remington Arms Company, Inc., Bridgeport, Conn., a corporation of Delaware Application March 3, 1949, Serial No. 79,368

(Cl. Sil-190) 13 Claims.

This invention relates particularly to a nrearm of the type which is automatically reloaded and made ready for a subsequent shot by utilizing the energy of recoil imparted to a movably mounted barrel. Typical rearms of the prior art having these characteristics are shown, for example, in the following patents of the late John M. Browning: Nos, 659,507, 689,283, and 710,094, to which reference may be made for the general principles underlying the construction of such firearms. Reference will also be made to Rutherford Patent No. 2,278,589 for certain features incorporated in the firearm exemplifying the invention.

The principal objects of this invention are the .provision of a rearm of this type having an @improved streamlined appearance and the provision of such a rearm which can be eiciently and economically manufactured.

In general, these objectives have been accomplished without change in the operating principles exemplied in the Browning patents and largely by such expedients as changing the exterior shape of the receiver and fitting thereinto parts of simplified design having functions equivalent to those of the Browning designs.

The exact points where the improved arm differs inventively fromV the Browning designs, as well as other objects and advantages thereof, will appear from consideration of the following specification and claims, referring to the attached drawings in which:

Fig. 1 is a vertical longitudinal sectional view showing the action in breech closed and locked position. l Fig. 2 is a similar view showing the action in breech open position.

Fig. 3 is a similar view showing the action in an intermediate position during the closing of the breech.

Fig. 4 is a cross-sectiona1 view taken on the plane indicated by the line 4--4 in Fig. 2.

- Fig. 5 is a longitudinal horizontal sectional Vview taken on the plane indicated by the line section of the trigger plate assembly, portions General description Referring to the `drawings by characters of reference, it may be seen that the firearm comprises a receiver I0 to which a buttr stock Il is secured. The receiver serves as the main frame of the rearm and .at the same time provides a casing to enclose the working parts thereof. Secured in a'bore in the lower forward wall of the receiver and extending forwardly therefrom is the cylindrical magazine tube I2. A barrel I3 is provided with a barrel guide ring I4 encircling the magazine tube and with a barrel extension I5 which isl received within the receiver and guided for reciprocation therein by feet I6 and II received respectively in tracks I8 and I9 formed in the inner side walls of the receiver, As in the Browning patents, a recoil .spring 20 encircles the magazine tube and by engagement between the receiver and barrel guide ring, acts to maintain the barrel in a forward position.

Within the receiver a breech Vbolt 2l is slidably supported on feet 22 and 23 engaging the receiver tracks I8 and I9 in position to close the breech end of the barrel. A breech bolt slide 24 provides a pivotal mounting for a breech bolt locking block 25 and is supported for reciprocation in the tracks I8 and I9 by rails 26 and 27 formed on the sides of the slide. Right and left links 28 and 29 are pivotally attached to the slide in laterally spaced relation and extend rearwardly into engagement within the cupped end of the action spring follower 30. The action spring follower 30 is supported for reciprocation in an action spring tube 3I which has the double function of serving as a butt stock bolt and as a housing for theaction spring 32. This spring acts\ to urge the breech bolt into breech closed position.

The bottom of the receiver is partially closed by a trigger plate 33 in which there are mounted the trigger 34, hammer 35, carrier 36, and their associated parts. Front and rear trigger plate pins, 3l and 38, respectively, pass through the opposite side walls of the receiver and through holes in the trigger plate bushed respectively by bushings 82 and 38a to retain the assembly. The trigger plate `is provided with suitable de- 3 tents to prevent the accidental removal of either of the pins.

Barrel mounting The arrangement for supporting the recoiling barrel I3 is probably obvious from the foregoing general description' but a few details may be added for completeness. Between the barrel guide ring I4 and the barrel recoil spring 20 there may conveniently be located a friction brake assembly which is a modification of those employed by Browning. This brake consists of a split cylindrical friction piece 39 received inr a counterbore 40 in the guide ring in engagement with a conical shoulder 4I dening the end of the counterbore.

surfaces 42 or 43 on a friction control ring 44. By the selection of the conical surface '42 making the smaller angle with the axis of the magazine tube, a greater percentage of the recoil forcewill appear as a radial component, causing the friction piece to grasp the tube more firmly andl compensate for the more severe recoil of heavy loads. A wooden fore-end 45 slips over the magazine tube to provide a gripping surface and to serve as a housing for the barrel recoil spring. This fore-end is preferably lined .with a sheet metal liner.46 which fits over a fore-end support block 41 on the front wall of the receiver and which has formed integrally therewith a barrel return stop bushing 48. A magazine cap 49 screws onto the end of the mag- The rear end of theV friction piece is engaged by one of `the conical azine tube and is there retained by any suitable detent means, not shown, to secure thevfore-end in place and provide a positive stop for the barrel return. Within the magazine tube there are provided the usual magazine spring 58 and magazine follower I. Stop shoulders 5Ia, provided in' the receiver adjacent the rear end of the magazine tube I2, serve to prevent expulsion of the' follower.

f :As noted in the general description, the forces 'of' recoil serve to move the barrel rearwardly pinto the receiver against the opposition of the barrel recoil spring as each shot is fired. Some "of the energy vof recoil is frictionally absorbed by the engagement of the friction ring with the magazine tube and the remainder is utilized to operate the action, as'will presently appear.

Breach locking action Asnoted in the general description, the barrel "extension I5, breech bolt 2I, and breech-bolt s1ide24'are all arranged' for linear reciprcat'ion guided in the tracks I8 and I9 formed in the receiver. slide 24 has capacity for limited fore and aft Vvmovement relative to the breech bolt and that 'the locking `block 25 is pivotally mounted there- "on. f"The forward end of the locking block is `formed to'deflne a flat surface 52, and a smoothly rounded corner surface 53. which the parts are shown in Fig. 1, the flat surface 52 is in engagement with a substantially `vertical rearwardly facing surface' 54 formed in It lwillA be noted that the breech bolt In the position in the breech bolt and the locking lug 55 is engaged within the slightly undercut locking recess 56 in 'the barrel extension. The action spring 32 act- ?-ing through the links 28 and 29 against the slide v24 tends to' maintain the parts in this condition.

Obviously, the breech bolt cannot be unlocked vpressure has dropped to a safe level.

a component of this force acting in the under= cut recess 56 tends to force the lug 55 on the block Y of their recoil excursion, the breech bolt slide 24 will be caught and retained in the rearward vposition'shown in Fig. 2. In this position a notch 51 in the lower surface of the slide 24 is engaged `by the detent 58 on the carrier dog 59. The car- Arier dog is pivotally mounted on the carrier 36,

which at this `point in the cycle 0f operations is locked in place by means to be later described in connection with the shell feeding cycle. A carrier dog spring 68 acting through a follower 6I urges the carrier dog to swing clockwise as viewed in Figs. l, 2, and 3, to insure that the slide will be caught thereon.

If the recoiling barrel has any excess of momentum above that absorbed by the friction piece and required to carry the mechanism rearwardly, toa point where the slide will be picked Aup by the carrier dog, the barrel and breech bolt will be stopped by the rear wall of the receiver, and the barrel recoil springY 2D will immediately return the barrel to its normal forward position. As it does so, it will be apparent that, with the `slide held on the carrier` dog detent 58, the locking lug recess 56 in the barrel extension will pull forward on the lug 55 and a force will be exerted tending to rotate the locking block clockwise about the point of its pivotal support on the then stationary slide 24 which will unlock the breech bolt from the barrel extension. Asa function o f this unlocking movement, the breech bolt 2| will move forward relative to the slide 24, then locked by the carrier dog 58, for a distance slightly under 1/8 inch and, in the event that the firing pin 62 has not been retracted by its retracting spring 63y the safety abutments 64 on the slide will en- Y gage the enlarged head 65 of the firing pin to positively cause such retraction. This engagement also has an important safety function in that it positively prevents forward movement of -the firing pin sucient to re a shot shell primer until the breech bolt is positively 'locked to the barrel extension. A firing pin retainer pin 56 seated in a vertical bore in the breech bolt engages a cut-away portion Blof the firing pin hea to vprevent disassembly thereof.`

A conventional extractor 68 spring-loadediby spring 691acting throughplunger I0 serves by engagement with a shot shell rim to retain a red Shot shell in rearward position engaged `with the face of the bolt 24 as the forwardly moving barrel is stripped from it. Immediately after the open .end of the shell clears the chamber mouth, an ejector II mounted onthe rear end of the barrel extension hooks the rear face of the shell at a point almost diametrically. opposite the extractor and flips the shell laterally through a conventional ejection port in the side wall of the receiver.

To avoid complicating consideration of the breech lockingr action with other-operations, it will only be noted that the carrier is released soon afterI the barrel returns to its forward posi-V -tion by means which will be more fully described Vvin connection with the shell feeding operation.

When the carrier is so released, the breech bolt slide 24`and breech bolt 2I are driven forward by the action spring 32 through the position shown in Fig. 3 to return to the position shown in Fig. 1. AAs the parts reach the position shown in Fig. 3, the rounded corner 53 on the locking block is in engagement with the surface 54 of the breech bolt at a, point such that a line between this point of contact and the point at which the locking block is pivotally attached to the slide makes an angle a, shown between the dot-dash lines von Fig. Y3, of substantially less than '90 degrees with the surface 54. The resultant force R, applied by the -spring 32 acting through the links 28 and 29, the slide 24, and the locking block 25 pivotally mounted on the slide, may, as shown in Fig. l1, be resolved into two components.` One component H acts along the axis of movement of the slide, tending to move the rbreech block forward. The other component V acts vertically upward at right angles t0 the movement of the slide and tends to rotate the locking block upward or counter-clockwise. At the forward limit of movement of the breech bolt, the locking lug 55 is opposite the recess 55 in lthe barrel extension and the force component V. referred to above, rotates the llocking block to lock bolt and barrel extension together. Ibe noted that as the lug 55 enters the recess 55 the angle a becomes more acute and the cornponent V increases proportionately, accelerating -and insuring the completion of the movement into locked position.

The cycle described above is repeated after each shell is fired.

To permit manual opening of the breech bolt, an elongated opening 13 is formed -in the side of the breech bolt, which is exposed through the ejection port. An operating handle 14 passes through this opening into engagement with a Vsnug-ly fitting aperture 15 in the breech bolt slide. Spring-urged detent means 16 in the slide engage an appropriate depression in the handle shank to releasably secure the parts. Theoversize opening 13 permits the relative movement between slide and breech bolt required to unlock the action. To permit the full length of recoil of the breech bolt, an operating handle slot as used in the Browning designs may intersect the ejection port and extend rearwardly therefrom. Whenever the barrel is removed, asin taking down the gun for cleaning or packing, the breech closing spring will urge the slide forwardly and the oper--V -atinghandle may engage the forward edge of the "ejection port, thus preventing inadvertent rer'noval of the breech bolt. A deliberate effort to remove the operating handle will overcome the detent 16, allowing the handle to come free,

whereupon the breech bolt assembly with the attached links may be removed from the receiver for cleaning or inspection.

Obviously the utility of this breech locking arrangement is not confined to a long recoil operated firearm, for it may be applied with equal facility to a short recoil action. Further, without modification of its essential locking principle, it may be applied to fixed barrel rearms of the gas operated or manually actuated types by coupling to the breech bolt slide either a gas pressure actuated operating rod or a manually actuated action bar or bars leading to a slidable fore-end.

Yiin the case of such a fixed barrel action, the recess in which the locking block lug is received might be formed either in the top wall of the receiver or in a stationary barrel extension. The essential feature is that the recess be located in vsome member of adequate strength which has a Afixed relationship to the breech face of the barrel.

It will 1 Shell handling The carrier 3B and carrier dog 59 have been y previously referred to in regard to their incdental function of temporarily locking the breech bolt slide in 'its rearward position. The primary function of 'the carrier is to effect a properly timed transfer of a loaded shell from the maga- Vzine tube i2 to a position infront of the forwardly moving breech bolt which then chambers the shell in the barrel. 'In performing this function, the carrier is assisted by the shell latch 18 and the combined shell latch and carrier latch v19. For more detailed discussion of the construction and operation of the carrier latch, reference may be had to Rutherford Patent No. 2,278,589. For the purpose of this specification, reference may best be made to Fig. 5 herein, which shows that the combined shell and carrier latch 19 is a long'itudinally extending member Lpivoted intermediate its ends on a carrier latch pivot pin supported in the right side wall of the receiver. A flat leaf carrier lat-ch spring '8l is .riveted or otherwise secured to the latch and engages the wall of the receiver to the rear of the pivot pin 8i), tending to swing the rear end of the latch into the receiver in a position in which it overlies the carrier 36 forward of the bushingI 82 which passes laterally through the trigger plate 33 and forms the pivot on which the carrier is supported. When the breech bolt, however, is in any other than its rearward or action-open position, as shown in Fig. 2, the carrier latch is held against the urging of its spring by means of an upwardly extending rib 83 formed at each end with a cam portion 8&3 and engageable with a downwardly extending control rib 85 formed on the lower surface of the breech bolt slide. Thus, when the action is open as in Fig. 2, the carrier latch is free to swing at its rear end into the receiver. In this position the carrier latch prevents the carrier from rising, and the carrier, through the medium of the carrier dog- 55, retains the breech bolt slide and breech bolt in action open position.

Two means are provided for releasing the carrier latch and hence allowing the action to close under 'the urging of the action spring 32. The rst of these means is manual, through the agency of the carrier latch button 86 which extends through a hole in the right side wall of the receiver and engages the carrier latch at a point forward of the pivot. The other means of releasing the carrier latch is automatic in operation and functions as a result of the release of a shell from the magazine by the shell latch 18 in a manner which will soon be described. When such a shell is released it springs rearwardly into the receiver on top of the lcarrier and since the rim at the head ofthe shell lis of a diameter nearly equal to the inside width of the receiver, engages the inner face 81 of the rear end of the carrier latch 19 and cams that portion outward and out of engagement with the upper surface of the carrier.

When the carrier is released, either manually or automatically, a component of action spring force acting through the carrier dog swings the carrier upwardly to position a shell in front of the forwardly moving breech bolt. After a short forward movement, the carrier dog tail 88 comes into engagement with the lower face of the breech bolt slide and causes the detent 58 to unhook from the notch 51 in the lower face of the slide. The carrier, however, remains raised until it is over-ridden by the slide, which occurs shortly after the complete disengagement of the carrier log from the lower face of the slide. At that point the carrier dog snaps upwardly, bringing the spring lthrust member 6| squarely under the step 89 on the carrier dog and applying the full force of the spring 60 to lowering the carrier. The carrier latch, however, does not snap out to lock the carrier down, as in the Browning guns previously referred to, but is held out by the control rib 85 on the slide. Thusl with the action closed, the carrier may be manually raised against the urging of the spring 60 to facilitate loading in the manner described in the Rutherford patent referred to.

With the carrier latch held against its spring by the control rib, the forward end thereof extends into the receiver and renders the shell latch portion 90 operative in retaining shells in the magazine. Since the carrier latch, as a whole, is made of fairly thin material and spring tempered, it will yield to permit a shell being loaded into the magazine to pass by, whereupon it will spring back to retain the shell.

The shell latch 18 comprises an elongated leaf spring received in a clearance cut in the left wall of the receiver and secured therein by engagement of a hole in its rear end with the forward trigger plate pin 31 and by lateral Yconnement between the trigger plate and the receiver. This latch is formed so that the natural tendency of its spring construction is to cause its front end 9| to extend into the receiver in position to oppose the release of shells from the magazine. This forward end is disposed fore and aft in a position to stop a shell at a position rearward of that in which it is supported by the latch end 99 on the carrier latch by a distance not materially greater than the thickness of a shell rim. An upward and forwardly extending finger 92 in the shell latch is disposed in the path of a downwardly extending control cam 93 on the lower surface of the left barrel extension foot |1. The interengagement of the control cam 93 and finger 92 is such as to retain the shell latch in an inoperative position whenever the barrel occupies its normal forward position. However, at any time during the recoil movement of the barrel, the shell latch is operative and serves to prevent the release of shells from the magazine. Y

In review of operations during the shell feeding cycle, it may be assumed that we start as would normally be the case with an empty gun in which the breech bolt is latched rearwardly in open position. One shell may be dropped through the ejection port 12, either into thecharnber of the barrel or on top of the carrier. AWhen the carrier latch .button is depressed,l the` carrier will swing upwardly and the breech bolt will moveto closed position. During the closing movement, the carrier will retire to its lower position where itrwill be held by its spring. One, or more additional shells may then be sequentially fed into the magazine through the open bottom vof the receiver, the carrier being raised during this operation usually by the engagement of the incoming shell with the lower face of the carrier. Each shell, in turn, is fed into the magazine past the shell latch 90 on the front end of the carrier latch and will be there retained.

When the chambered shell is fired, the barrel will recoil and the red shell will be ejected during counter recoil as described in connection with the breech locking operation. As soon as the barrel has recoiled about the shell latch controlled from the barrel extension will move out into position to stop the release of shells from the magazine. At a position of substantially full recoil, the carrier latch will be released from the control rib on the lower face of the breech bolt slide and its forward end willrrelease the rearmost shell in the magazine tothe shell latch 18. During the counter recoil of the barrel, the parts associated with shell feeding remain stationary until the control cam 93 on the barrel extension engages the shell latch linger 92. The rearmost shell is thereupon released and springs rearwardly into the receiver. As it does so, it encounters the face 81 of the carrier latch which it forces out o f engagement with the carrier. Simultaneously, the front end of the carrierlatch moves in to position the shell latch portion 90 in the path of the succeding shell in the magazine. As the carrier rises, it lifts the shell into a position in front of the forwardly moving breech bolt which chambers it and locks to the barrel extension, as previously described. While the carrier is raised, it serves to hold the carrier latch against the carrier latch spring 8|, and before the carrier has been lowered the control rib 85 on the slide will have engaged the retaining rib 83 on the carrier latch to take over this function.

The operation just described may be repeated until the last shell in the magazine has been chambered and i'lred. At that time, the same sequence is started again, but since there are no more shells in the magazine the carrier latch will not be disengaged from the carrier and the breech will remain open.

Fire control Referring particularly to Figs. 5 and 10, it will be observed that the trigger plate 33 forms with the carrier Vand fire control mechanism a complete sub-assembly which is removably secured in the receiver. This construction greatly facilitates manufacture, inspection, and assembly. The trigger plate proper is conveniently a die casting upon which a minimum of machine operations are necessary.

The trigger 34 is supported on a pivot pin 94 and is provided above the pivot with a pair of laterally spaced upwardly extending arms 95. A pivot pin 99 passes laterally through these arms and serves to pivotally mount a connector assembly comprising a right hand arm 91 and a left handV arm 98, both extendinggenerally forward from a point below the pivot pin 96. These arms` are secured together to act as a unit by means of their` common engagement upon pivot 96 and between the trigger arms 95, while they are required to rotate together as a result of the engagement of a button 99 struck up from the left hand arm with a hole |09 in the right hand arm. Intermediate the forwardly extending arms 91 and 98and the pivot 96, a spring seat button IUI is formed to receive one end of the combined trigger and sear spring |02. The other end of the sear spring has asimilar engagement with the scar |93 which is swingably supported on scar pin |04` and arranged to engage a hammer hook |95 formed onthe hammer 35. Obviously, the spring |02 acts between the trigger and Sear to urge the finger engaging portion of the trigger forward and to urge the sear forwardly into hammer lretaining position. At the same time, it acts to rotate the connector assembly clockwise as viewed in Fig. 10, with the result that the toeat the forward end of the right hand connector arm 91 tends to engage the bottom surface |03 of a recess c ut in the sear below the Sear pivot and, in rearof a connector abutment Il formed in the Searv surface |96. In thisA condition a normal pull upon the trigger serves to move the end. of connector arm 9.1 into engagement with the abutment IO'I and further movement causes the sear to. turn counter-clockwise on the sear pivot and release the hammer.

Doubling or the ring of repeated shots from one operation of the trigger is prevented by the provision of a clearance recess IBS in the sear to receive the. end of the connector arm after it has been disconnected from the abutment Illf. When this, has occurred, the trigger may be held back without eiect upon the sear, which will catch and retain the hammer the next, time it is cocked. Disconnection at each fall of the hammer is brought about by the disconnector H39, which has arearwardly extending tail I.I ll formed to engage beneath the. forward endof the left handv arm 98 of the connector assembly. The disconnector is supported by a disconnector pin II I ttedi in the trigger plate in a position which disposes an. arm I I2 on the disconnector in the path of the plunger H3, which communicates the force of the spring III to the hammer. Whenever the hammer falls, the plunger II3 engages the arm I I2, raising the tail I I and thus swinging the connector assembly counter-clockwise to disengage it from the sear.

To; furnish. additional safety, the disconnector I 09 is also. provided with a safety arm II5', which extends, forwardly and upwardly into a position whichwillbe. over-run by the breech bolt slide 24 whenever the slide is materially tothe rear of its fully'locked position. To insure thatthis control :y

is maintained atr all times except when locking is substantially complete, an inturned extension Ilia' is provided on the arm I I5 and disposed beneath a cam 29a formed on the breech bolt link.. Before the cam 29a, disengages from the extension II5a, the lower face of the slide will have engaged the arm proper.

summarizing, disconnection. will take place as a. result of hammer fall, and during the period in which the automatic loading cycle is being completed, willv be maintained by theengagement of the link cams or the` lower face of the slide with the arm II'5. The connector can only re-engage the sear after the breech is closed and locked, and even then, it cannot re-engage until the trigger has been released and allowed to return to its normal position. If, at any time thereafter, the breech is partially or fully opened, the cam 29a and the lower rear corner IIS of the breech bolt slide act in succession to urge the disconnectorto operate and disconnect the trigger from the'sear, thus preventing inadvertent firing from an open breech.

The normal type of cross bolt safety comprising a slidable bolt II'I in the trigger guard II8 is provided. This bolt is, in the usual way, provided with a body portion having two diameters and when disposed to extend to the right of the guard and obstructing the usual position of a trigger finger, the large diameter portion will obstruct the rearward movement of the trigger finger piece. A spring-urged detent I I9 mounted in the trigger plate releasably retains the safety in either position selected.

Summary The foregoing specification has been divided into sections each dealing with one of the principal trains of directly related parts and operations. In View of the general similarity of functioning between this arm and the prior artv arms, ex.- emplied by the Browning patents, it does not appear necessary to provide here av detailed account of the over-all operations of the gun. Each of the sections referred to above has included a summary of the operation of that mechansim, and the interrelation is believed to be obvious.

1 While a specific firearm embodying the invention has been described in detail, it is not intended that the invention should be considered as` limited to the exact structure illustrated. It is intendedv to include all equivalent devices and combinations within the scope of the claims appended hereto.

I claim:

l. In a firearm comprising a barrel having 'therein a cartridge receiving chamber, means rigidly securedv to said barrel and extending rearwardly from the mouth of said chamber, a charnber closing breech bolt reciprocable between a forward breech closing position and a rearward breechV open position, and an operator for said breech bolt comprising a slide reciprocable with and movable relative to said bolt; the combination of means for locking said' bolt in breech closing position comprising a locking block supported for rotation about a pivot on said slide from a breech locking position engaged with said barrel means to a breech unlocking position, and means for rotating said locking block to breech locking position comprising elements defining c0- operating surfaces on said locking block and breech bolt respectively, said surfaces being so rclativeiy inclined that pressure of either one upon the other urges said locking block toward breech locking position.

2. In a firearm comprising a barrel having therein a cartridge receiving chamber, means rigidly secured to said barrel and extending rearwardly from the mouth of said chamber, a cha-mber closing breech bolt reciprocable between a forward breech closing position and a rearward breech open position, and an operator for said breech bolt comprising a slide reciprocable with and movable relative to said bolt; the combination of means for locking said bolt in breech closing position comprising a locking block supported for rotation about a pivot on said slide from a breech locking position in engagement with saidI barrel means to a breech unlocking position, and means for rotating said locking block to breech locking position comprising an element of said bolt defining a rearwardly facing surface and an element of said locking block defining a surface adapted for line contact with said rearwardly facing surface,l the relative inclination of said surfaces being such that pressure of either surface upon the other surface urges said locking block toward breech locking position with a torque that increases as said locking block moves toward breech locking position.

' '3.' In a rearm comprising a barrel having therein a cartridge receiving chamber, means rigidly securedl to said barrel and extending rearwardly from the mouth of said chamber, ra

chamber closing breechbolt reciprocable between 'a forward breech closing position and a rearward breech open position, and an operator for said breech bolt -comprising a slide reciprocable with and movable relative to said bolt; the combination of means for locking said bolt in breech closing position comprising a locking block supported for rotation about a pivot in said slide from a breech locking position to a breech unlocking position, means for rotating said locking block to breech locking position comprising an element of said bolt dening a'rearwardly facingv surface adjacent the forward end of said breech bolt and an element of said locking block defining a surface adapted for line -contact with said rearwardly facing surface, the relative inclination of said surfaces being such that pressure of either one of said surfaces upon the other one of said surfaces urges said locking block toward breech locking position with a torque that increases as said locking block moves toward breech locking position, a lug on said locking block, and a shoulder on' said barrel means adapted for engagement by said lug when said locking block is in breech locking position'.

4. The combination described in claim 3, the relative inclination between said rearwardly facing surface and a line connecting said pivot with the point of line contact of said locking block surface with said rearwardly facing surface being substantially less than ninety degrees when said locking block is in breech unlocking position and reduced to a more acute angle when saidlocking block is in breech locking position.

5. The combination described in claim 4, including spring means -arranged for moving said slide toward breech locking position.

6. The combination described in claim 5, including means actuated by firing of a cartridge in said chamber for automatically moving said slide toward breech unlocking position and a manual operator directly connected to said slide for manually moving said slide toward breech unlocking position.

7. In a rearm comprising a spring-opposed recoiling barrel having therein a cartridge receving chamber, barrel extension means rigidly secured to said barrel and extending rearwardly from the mouth of said chamber, a chamber closing breech bolt reciprocable withl and relative to said barrel along a path parallel to the line of recoil of said barrel between a forward breech closing position and a rearward breech open position, an operator for said breech bolt comprising a slide reciprocable with and relative to both said barrel and bolt along a path parallel to the line of recoil of said barrel, and spring means arranged to urge said -slide forwardly; the combination of means for locking said bolt to said barrel extension in breech closing position comprising a locking block supported for rotation about a pivot in said slide from a breech locking position to a breech unlocking position, means for rotating said block to breech locking position comprising an element of said bolt defining a rearwardly facing surface and an ele- 1- tion, whereby when said spring urges the slide 12 forwardly said locking block lug will' engage in front of the shoulder on said barrel extension as a result of the contact between said surfaces and will remain so engaged as long as one of said surfaces exerts pressure on the other of said surfaces. Y

8. The combination described in claim 7, the relative inclination and dispositionof said contacting surfaces being such thatthe torque urging said locking block toward breech locking position will increase to a maximum as said locking block'reaches breech locking position.

9. The combination described in claim 8, the relative inclination between said rearwardly' facing surfaceand a line connecting saidpivot with the point of sliding contact of said locking block with the rearwardly facing surface being substantially less than'ninety degrees when the locking block is in breech unlocking. position and reduced to a substantiallyV more acute angle when said locking block is in breech unlocking position. r

10. The combination described in claim 9, including a manually operable member directly attached to said slide to` manually move same rearwardly, whereby said surfaces no longer exert pressure upon each other vand said locking block may move to breech unlocking position. l

11. The combination described in claim 10, said slide having limited capacity for reciprocation with respect tosaid breech bolt andv arranged to move the bolt rearwardly with the'slide Vwhen said locking block is in breech unlocking position.

12. The combination described in claim 1l, wherein said breech bolt has a'laterallyf extending slot' formed therein and said manually operable member passes through said 'slot with 'sufcient clearance'to permit relative reciprocation between said slide and the breech bolt while preventing inadvertent disassembly of said slide and bolt.

13. The combination described in claim 12, wherein a firing pin having a shoulder is mounted in said breech bolt and safety abutments are provided on said slide enga'geable 'with said shoulder to positively retract-and to retain said firing pin in a rearward position in the bolt when the locking block is in breech unlocking position.

` LEXIE RAY CRITTENDON.

REFERENCES CITED The following references areof record 'in the file of this patent:

UNITED STATES PATENTS..

OTHER REFERENCES f ser. No. 306,568, Prola (A. P. o. ,vpub1ished April 27, 1943.

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