US 3633302 A
A revolver-type of firearm includes a frame having a cylinder recess, a barrel located at the forward end of the frame, a crane pivotally connected to the frame and a cylinder rotatably mounted on the crane and normally received in the cylinder recess. A spring-biased extractor is slidably mounted in the cylinder and includes a cartridge rim-engaging member and a ratchet located at the rear end of the cylinder. A spring-biased detent element positioned in the frame cooperates with a detent recess in the center of the ratchet to resiliently hold the rear end of the cylinder in position relative to the frame. A hand operated by the hammer acts upon the ratchet to rotate the cylinder to bring succeeding cylinder chambers into alignment with the barrel each time the hammer is moved from a fired to a cocked position and the spring-biased ball yields, if necessary, to allow a slight lateral movement of the cylinder to accommodate any mechanical mismatch or interference between the hand and the ratchet. A thumb operated latch on the crane releasably locks the crane to the frame.
Claims available in
Description (OCR text may contain errors)
ilnite States atent Karl R. Lewis 77 Olney Road, Wethersfield, Conn. 06109  Appl. No. 15,070
 Filed Feb. 27, 1970  Patented Jan. 11, 1972  Inventor  CYLINDER MECHANISM FOR REVOLVER-TYPE 1,518,027 12/1924 Vosmek 42/62 Primary Examiner-Benjamin A. Borchelt Assistant Examiner-Cv T. Jordan Attorney-McCormick, Paulding & Huber ABSTRACT: A revolver-type of firearm includes a frame having a cylinder recess, a barrel located at the forward end of the frame, a crane pivotally connected to the frame and a cylinder rotatably mounted on the crane and normally received in the cylinder recess. A spring-biased extractor is slidably mounted in the cylinder and includes a cartridge rim-engaging member and a ratchet located at the rear end of the cylinder. A springbiased detent element positioned in the frame cooperates with a detent recess in the center of the ratchet to resiliently hold the rear end of the cylinder in position relative to the frame. A hand operated by the hammer acts upon the ratchet to rotate the cylinder to bring succeeding cylinder chambers into alignment with the barrel each time the hammer is moved from a fired to a cocked position and the spring-biased ball yields, if necessary, to allow a slight lateral movement of the cylinder to accommodate any mechanical mismatch or interference between the hand and the ratchet. A thumb operated latch on the crane releasably locks the crane to the frame.
BACKGROUND OF THE INVENTION This invention relates to revolver type of firearms, and more particularly to a cylinder mounting and operating mechanism for such firearms.
Revolver-type firearms have a rotating cylinder with chambers therein which carry the cartridges to be fired. One of a revolvers basic functions isto align a new chamber of the cylinder with the barrel during each cocking movement of the hammer so that a fresh cartridge is brought into firing position for firing when the hammer is next released from its cocked position. To achieve this the cylinder is usually rotated by a ratchet and hand mechanism which angularly indexes the cylinder one chamber position each time the hammer is cocked, the hand usually being connected with the hammer for movement therewith. A common malfunction of a revolver type of firearm is its failure to index properly or to accurately line up a new cylinder chamber with the barrel each time the cylinder is rotated. When such a malfunction is present the revolver is said to be out of time. Proper timing or indexing of the cylinder motion can usually only be achieved by hand filing and fitting of the ratchet-hand mechanism, usually at the firearm factory. Due to wear a revolver-type firearm may become out of time after repeated usage, and if this occurs the ratchet usually must be replaced, preferably at the factory, and this again requires expert workmanship to properly fit and adjust the ratchet-hand relationship to reestablish a proper timing.
In most revolvers the hammer operates the hand in such a manner that the hand travels in a given straight line path of movement as the hammer is cocked. During its excursion along this path of movement the hand first engages a first abutment surface of a dog on the ratchet and through such engagement rotates the cylinder to its new position, after which the cylinder latch engages the cylinder to hold it in its new position. The cylinder reaches its new position, and the cylinder latch is moved into latching engagement with the cylinder, before the hand completes its movement, and after the new position is reached the hand, in continuing on its movement, slides past the same or another abutment surface. One of the ratchet-hand relationships which it is normally necessary to maintain is the relationship between the hand and this latter abutment surface since if the latter abutment surface is improperly located a lateral force will be exerted on the ratchet tending to push the rear end of the cylinder sideways out of the cylinder recess thereby possibly producing binding or jamming and quickly producing undesirable wear on the hand and abutment surfaces. In such revolvers it is therefore extremely desirable that the cylinder at the end thereof containing the ratchet, which is normally its rear end, be able to move resiliently laterally after being indexed to and locked in its proper angular position while the hand continues the remainder of its movement so that undue wear or jamming of the mechanism does not result.
In addition, many revolvers have undesirable vibrations associated with the discharge of the firearm. This is partially due to the fact that there is usually some small clearance or looseness between the cylinder and the frame or other adjacent structure with the result that when a cartridge is fired the cylinder is suddenly thrust forwardly against the frame or other adjacent structure with great force causing it to rebound and vibrate.
The general object of this invention is therefore to provide a cylinder mechanism for a revolver type of firearm which among other things allows the cylinder to move slightly laterally under a resilient bias as the hand moves along its path of travel to accommodate any slight misfits existing in the ratchet-hand relationship, this means therefore eliminating the need for precise hand adjustment of the ratchet-hand relationship at the time of manufacture and/or repair and also reducing wear on the parts so as to reduce the frequency of required repairs.
Another object of the invention is to provide a cylinder mechanism of the aforementioned character which also acts to exert a forwardly directed bias on the rear end of the cylinder so as to resiliently hold the front end of the cylinder against the frame or other adjacent stop structure to thereby minimize undesired vibrations at the time of firing.
SUMMARY OF THE INVENTION The present invention involves a revolver type of firearm having a frame and a cylinder rotatably supported in a frame recess by a crane pivotally connected to the frame for loading and unloading the cylinder chambers. The invention resides in a spring-biased detent element carried by the frame and normally received in a cooperating detent recess in the center of the rear end of the cylinder. The spring-biased detent element in cooperation with the detent recess biases the rear end of the cylinder laterally to a neutral position from which the rear end of the cylinder may move slight distances to either side to accommodate slight misfits or maladjustments between the dog or abutment surfaces on the ratchet and the hand which moves the ratchet. The spring-biased detent element exerts a resilient restoring force on the rear end of the cylinder to return it to its neutral position after it is displaced to accommodate the hand travel, and it also exerts a forwardly directed biasing force on the cylinder tending to hold the front end of the cylinder tightly against the frame or other stop structure so as to reduce vibrations when a cartridge is fired.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side-elevational view of a revolver type of firearm embodying the present invention.
FIG. 2 is another view of the firearm of FIG. 1 with the upper portion thereof being shown in vertical longitudinal section and with the lower portion being shown in elevation, the illustrated grip side plate being partially broken away to reveal more of the structure of the frame.
FIG. 3 is an enlarged view of the cylinder mechanism portion of FIG. 2.
FIG. 4 is a sectional view taken on the line 44 of FIG. 3.
FIG. 5 is a sectional view taken on the line S5 of FIG. 3.
FIG. 6 is a sectional view taken on the line 6-6 of FIG. 3.
FIG. 7 is a sectional view taken on the line 77 of FIG. 6.
FIG. 8 is a fragmentary sectional view taken on a plane equivalent to that of FIG. 3 through a firearm comprising another embodiment of this invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention in its preferred form, and as illustrated herein, relates to a revolver type of a hand gun. However, it should be understood that the invention is also applicable to revolver type of shoulder guns and other revolver firearms. Except as it relates to the cylinder support and operating mechanism the illustrated firearm is generally similar to that shown and described in US. Pat. No. 3,163,951, entitled Firearm Firing Mechanism, to which reference may be made for a more complete understanding of the construction and operation of the firing mechanism and other pans which do not by themselves constitute a part of the present invention.
Referring first to FIGS. 1, 2 and 3, the revolver illustrated therein is shown generally at 10. This revolver has a frame 12 with a mechanism cavity 14, a cylinder recess 16 and a crane cavity 18. An intermediate wall 20 separates the mechanism cavity 14 from the cylinder recess 16. A crane 24 is pivotally mounted on the frame 12 by means of a cylindrical stem 26 which is integral with the remainder of the crane and which is received in a conforming bore formed in the frame. The crane rotatably supports a cylinder 28, as hereinafter explained in more detail, for rotation about an axis extending longitudinally of the frame and the crane is pivotally movable relative to the frame from its illustrated normal position, at which the cylinder is located within the cylinder recess, to a position at mounted on the frame 12 within the mechanism cavity 14, by
being received on a pin-48, and is spring biased. toward the illustrated fired oruncocked position of FIG. 2 by a Ushaped mainspring 50. The hammer cooperates with a firing pinv 52 which is slidably mounted. in a herein the intermediate frame wall 20. It is held in the bore by'a press-fit plug 56 having an opening therein through which its forward end passes to strike a cartridge, and is biasedrearwardly by aspring 58 so as to be tioned in front thereof by the cylinder. The hammer 46 also has mounted thereon a hand 60having a finger 64 atits free end which engages a ratchet 65 at the rear end of the cylinder 28 to rotate the cylinder one chamber position each time the hammer is cocked to bring a new chamber'of the cylinderinto, alignment with the firing pin 52 and the barrel 66 which is v located in front of the cylinder. The'hand is biased toward the- I rear end of the cylinder by a spring 67 received in the hammer and acting on a pin 68 connected with the hand, the hand being pivotally connected to the hammer by'another pin 69;
The hammer, 46 is operated ,by' a trigger-actuated. firing mechanism indicated generally at 70 in FIG. 2. The mechanism 70 includes a trigger 72 pivotally connected to the frame 12 by a pin '74 and having a lip 84 thereon which operatively engages a lip-85 on a cylinder latch 86. The cylinder latch in turn is mounted forsliding and angular movement relative to the frameby means of a pin: 90 fixed to the frame and anelongated slot in they latch through which the pin extends. The latch 86 has a head 92 which protrudes into the cylinder recess and normally engages one of a series 'of notches 100, 100 in the cylinder to hold the cylinder in an angularly position at which one of its chambers is aligned with the barrel. The head 92 of the latch 66 is biased toward the cylinderby a spring 96. When the trigger is pulled rearwardly its lip 84 first pivots the cylinder latch 66, in the counterclockwise direction as viewed in FIG. 2, to withdraw the head 92 from the associated notch 100 and thereby to free the cylinder for rotation by the hand 60. After the trigger has moved some distance rearwardly its lip 84 passes beyond the lip 85 of the latch and allows the latch to be returned to its locked position by the spring 96, the cylinder at this time having been rotated to a new chamber position and the head 92 of the latch being received in a new notch 100 to lock the cylinder in such new position. Also, as the trigger 72 is moved to a rearward position the hammer is also moved to a cocked position and then, at the end of the rearward trigger movement, the hammer is released for movement to its forward position under the influence of the main spring 50 to cause the firing of the cartridge positioned in front of the firing pin 52. This is assuming that the firearm is set for operation in a socalled double action manner wherein one pull of the trigger both cocks and releases the hammer. The illustrated firearm may also be set for operation in a single action" manner wherein one pull of the trigger cocks the hammer and a second pull of the trigger releases the hammer for firing. As mentioned, the illustrated firearm is similar to that shown in US. Pat. No. 3,163,951 and reference may be made to said patent for a more complete understanding of the construction and operation of the firing mechanism.
The barrel 66 has a threaded rear end portion 102 which is threadably received in the frame 12. Forwardly of the frame 12 is a shroud 104 having a bore therein which receives the barrel, the barrel having a flange 106 on its forward end so that the shroud is axially held in place between the flange 106 and the forward end of the frame. By engagement with the crane 24 the shroud also holds the crane in place in its recess.
. normally held away from the rear surface of the cartridge posi-' cylinder bore and the flange 204 and normally biases the rods I I 108 and 114i forwardly to hold the retractor plate [16in engagement with the rear face of thecylinder as iliustrated.
The retractor plate 116, as shown in'Fl'GS. 3 and 5, includes I I radially extending fingers E20, 120 which lie adjacent and par- I The shroud is prevented from rotating relative to the frame and'barrel by means of a locking pin. (not shown) passing between the forward end of the frame and the rear end of the shroud.
I I Turning now to FIGS. 3 to 7 for a more detailed description of the cylinder mountingand operating mechanism of the firearm 110, the cylinder28 has alongitudinal bore 108 passing therethrough and'is mounted on the crane 24. for rotation about a longitudinal axis by means of a cylindrical sleeve 110 fixed at its forward end to the'crane and rotatably receiving the cylinder bore'along its rear end portion. Slidably mounted I in the sleeve 110 is an ejector mechanism consisting of a forward rod 112 and a'rear rod IN. The forward rod 112 is threadably connected at its rear end to the forward end of the rear rod, as shown best in FIG. 3, and includes a fiange'ZM fixed thereto slightly forwardly of the forward end of the rear rod. The rear end of the rear rod 116 passes through the rear end of the cylinder and has integrally connected thereto a I I I I retractor plate 116. A biasing spring 118 surrounding the rear rod 114 is compressed between the rear end wall of the tially surround the rear ends of the chambers 30,30 and are received in appropriate depressions'in the rear face of the cylinder. These fingers are normally located in front of therims of the'cartridges received in the chambers and upon the rearward movement of the extractor plate engages such car-' tridge rims to pull thecartridges, or the empty shells thereof, fromthe chambers. Of course, in order. to extract the cartridges from the chambers the crane and'cylinder are first pivoted to a position at'which the cylinder is located at one side of the frame as is conventional. 'When the crane and cylinder are moved to such sidewise displaced position the forward ejector rod 112 may be grasped manually and pushed rearwardly to movethe'retractor plate 116 rearwardly to remove the cartridges from the chambers. The firearm may then be reloaded and the crane'member and cylinder returned to their normal positions as illustrated. I I I The crane 24 is locked in its illustrated normal position by means of a manually operated latch shown best in FIGS. 6 and 7. This latch comprises a thumb-engagable member 122 which is slidably receivable in a slot 124 in the crane for movement in a generally vertical direction relative thereto as viewed in FIG. 6, the slot and the portion of the latch member received therein being generally T-shaped. A compression spring 126 of a generally rectangular shape as viewed from either end is also received in a part of the slot and engages the latch member, as shown best in FIG. 6, to urge it upwardly, and a pin 128 passing through the crane and a vertically elongated notch in the latch member limits the vertical movement of the latch member in each direction. At its upper end the latch member includes a tongue 130 which is receivable in a notch 132 in the frame 12 to releasably hold the crane in its illustrated normal position. From FIG. 6 it will of course be understood that the latch member 122 may be moved downwardly from its illustrated position to remove the tongue 130 from the notch 1132 thereby freeing the crane 24 for movement to its sidewise displaced position for loading and unloading of the cylinder.
The retractor plate 116 also includes the ratchet 65 which, as shown best in FIG. 5, is comprised ofa number of dogs 134, 134, there being one such dog for each of the cylinder chambers 30, 30. Each dog is separated from the next succeeding dog by a recess 136 and includes a first abutment surface 138 and a second abutment surface M0. As shown in FIG. 5 the finger 64 of the hand 60 travels in a vertical path displaced slightly to the right of the center of the barrel of the cylinder and rotates the cylinder 23 in the counterclockwise direction as indicated by the arrow. In FIG. 4, the solid lines show the hand 64 in the lowermost extent of its path of travel and the broken lines show it in the uppermost extent of its travel, and it will be noted from this figure that the finger 64 travels in a vertical slot 141 of the frame which engages both of its sides and restrains it against lateral displacement. In FIG. 5 the dog 134 indicated at A is the one positioned to be next engaged and driven by the finer 64 as such finger is raised from its illustrated lowered to its illustrated raised position. In considering the dog A it will be noted that its abutment surface 138 is so located as to be initially perpendicular to the path of movement of the finger 64. Therefore as the finger 64 moves upwardly it engages the surface 138 and through engagement with such surface rotates the ratchet and the cylinder. As the ratchet and cylinder are rotated by the upward movement of the finger 64 the dog A is eventually brought to the position at which its second abutment surface 140 is in line with the path of the movement of the left-hand side of the finger 64, as is the case with the corresponding surface of the illustrated dog B. Thereafter the finger 64 slides past the surface 140 in continuing its upward movement but causes no further rotation of the ratchet and cylinder. Also, as the cylinder reaches its new position the head 92 of the cylinder latch 86 is moved into locking relationship with the cylinder 28 to lock it against any further rotation. In order that the finger 64 may continue its upward movement after the cylinder is locked by the cylinder latch it is normally necessary that the surface 140 be accurately aligned with the path of travel of the finger 64, and if the proper relationship is not present the hand will tend to displace the ratchet and the cylinder sidewise or to the left in FIG. 5 causing undue wear of the hand and dogs and possibly causing a jamming of the parts.
To avoid the above-stated requirement for an accurate relationship between the dog surfaces 140, I40 and the path of travel of the hand 64 the rear end of the cylinder 28 of the illustrated firearm is supported relative to the frame 12 by a spring-biased ball detent which allows such rear end of the ratchet and cylinder to move a slight distance laterally under a bias force to accommodate any slight interference between the hand finger and the ratchet dogs. Referring to FIG. 3, this spring-biased ball is indicated at 142 and is received in a recess 144 in the intermediate wall 20 of the firearm frame. The forward end of the bore 144 is of a slightly smaller diameter than the ball 142 so that a portion of the ball extends forwardly beyond the forward face of the wall. Behind the ball is a helical compression spring 146 which works between the ball and a plug 148 press fitted or otherwise fixed in the rear end of the bore.
For cooperation with the ball 142 the retractor plate 116 of the cylinder 28 includes a conforming spherically or conically shaped detent recess 150. Under normal conditions the ball 142 is pressed by the spring 146 into the detent recess 150 and rests against the surface of such recess to hold the rear end of the cylinder and the retractor plate in a truly centered position relative to the frame. However, due to the cooperation between the ball and the detent recess the rear end of the cylinder may be displaced a slight distance to either side of its truly centered position to accommodate a mismatch in the fit between the ratchet dogs and the finger 64 of the ratchet operating hand 60, the ball 142 during such movement being slightly displaced in the rearward direction.
As mentioned, the ball 142 normally rests against the surface of the detent recess 150 and therefore it exerts a forwardly directed biasing force against the rear end of the retractor plate and, through the retractor plate, against the cylinder to urge the cylinder forwardly. The forward end of the cylinder in turn includes an annular shoulder 152 which is held by the biasing resiliently in engagement with the adjacent stop structure. Actually the forward face of the shoulder 152 overlies part of the frame 12 and part of the crane 24 and either the frame or the crane may be designed to absorb the forward force applied to the cylinder, or both parts may share such force.
The ball 142 represents one type of detent element which may be used in firearms embodying this invention, and such detent element may take various other forms without departing from the broader aspects of the invention. FIG. 8, by way of example, shows one such other form of detent element. Referring to this figure, the detent element there shown constitutes a part 154 received in the frame 20 and having a head 156 with a forwardly directed spherical face which engages the detent recess in the retractor plate 116. Rearwardl y of the head 156 the part includes a stem I58 surrounded by a spring 160 which biases the part forwardly. The rear end of the stem 158 passes through a reduced diameter section of the associated frame bore and has a collar 162 threaded or otherwise fixed thereto. The collar 162 is located beyond the rear face of the adjacent frame wall 20 and is engageable therewith to limit the forward movement of the part 156 when the cylinder is swung to its loading position and out of engagement with the part 156.
I. In a revolver type of firearm the combination comprising a frame having a cylinder recess, a cylinder, means for supporting said cylinder so as to normally reside in said cylinder recess and to be rotatable about a longitudinal axis extending generally longitudinally of said frame, a ratchet at one end of said cylinder, means defining a detent recess at said one end of said cylinder located generally centrally thereof, a detent element carried by said frame adjacent said detent recess for movement relative to said frame generally parallel to said longitudinal axis toward and away from said detent recess, a spring for urging said detent element toward and into engagement with the said detent recess, said detent recess and said detent element having such shapes in the vicinity of their points of coengagement that as a result of a force tending to move said recess laterally relative to said detent element said detent element is moved by a camming action relative to said frame in the direction away from said recess to permit said recess and said one end of said cylinder in which it is formed to move laterally of said frame under the influence of said lateral force, and a hand supported in said frame and engageable with said ratchet to rotate said ratchet and said cylinder at a predetermined time in the operating cycle of said firearm.
2. In a firearm the combination defined in claim 1 further characterized by said detent element have a generally spherical face for reception by said detent recess.
3. In a firearm the combination defined in claim 1 further characterized by said detent element comprising a ball.
4. In a firearm the combination defined in claim 1 further characterized by said detent element comprising a part slidably received in a bore in said frame, said part including an enlarged head having a generally spherical face for reception by said detent recess and a stem of smaller diameter than said head, said frame bore including one portion for slidably engaging said head and a smaller diameter portion for slidably engaging said stem, a spring surrounding said stem and located in said one portion of said frame bore between said head and one end of said smaller diameter portion of said frame bore, and a collar means connected to the end of said stem opposite from said head for engaging said frame to limit movement of said part relative to said frame in the direction toward said detent recess.
5. In a firearm the combination defined in claim 1 further characterized by said means for rotatably supporting said cylinder comprising a crane pivotally connected to said frame, said crane being located adjacent the forward end of said cylinder, said ratchet being located at the rear end of said cylinder, said frame including a wall behind said rear end of said cylinder, said detent element and said spring being received in a bore in said wall and said detent element having a forwardly directed generally spherical face which protrudes forwardly beyond said wall, and stop means for limiting the forward movement of said detent element, said detent recess being so shaped and placed that when said detent element is in engagement therewith it is held out of engagement with said stop means that the full force of said spring is applied through said detent element to said cylinder.
6. In a revolver type of firearm the combination defined in claim further characterized by a barrel received in said frame and extending forwardly from the forward end of said cylinder, said cylinder being engageable at its forward end with the rear end of said barrel and normally held in such engagement by the bias force exerted thereon by said spring through said ball.
7. In a revolver-type firearm the combination as defined in claim 5 further characterized by said crane being movable relative to said frame between a normal position and a second position at which second position said cylinder is positioned to one side of said frame to permit the loading and unloading of cartridges, said crane including a normally operable latch engageable with said frame for releasably retaining said crane in said normal position.
8. In a revolver-type firearm the combination defined in claim 5 further characterized by said cylinder having connected therewith an extractor mechanism comprising a retractor plate located at the rear end of said cylinder and a rod means connected with said retractor plate and passing forwardly through and beyond said cylinder and said crane, and a compression spring located within said cylinder and surrounding said rod means for urging said rod means and said retractor plate forwardly relative to said cylinder, said retractor plate including said ratchet and said detent recess.
9. In a revolver-type firearm the combination defined in claim 8 further characterized by said retractor plate including fingers positioned to engage the rims of cartridges received in the chambers of said cylinder for extracting such cartridges as said retractor plate is moved rearwardly relative to said cylinder.
10. In a revolver-type firearm the combination defined in claim 1 further characterized by said cylinder having a plurality of chambers, said ratchet including a dog for each of said chambers of said cylinder with each of said dogs having a first surface and a second surface which first and second surfaces are engaged by said hand at different times throughout the movement of said hand in one direction along its path of movement, the first of said surfaces being arranged so as to initially be arranged generally perpendicular to said path of 40 Said cylinder" movement of said hand so as to be engaged thereby and to cause rotation of said ratchet and said cylinder while said hand remains in moving engagement therewith, and the second of said surfaces being arranged so as to reside generally parallel to said path of movement of said hand and to be engaged by the side of said hand as said hand traverses the final portion of its path of movement.
Ill. In a revolver-type firearm the combination comprising a frame having a cylinder recess, a cylinder, means for supporting said cylinder in said cylinder recess for rotation about an axis extending longitudinally of said frame, a barrel connected with said frame and extending forwardly from the forward end of said cylinder, stop means engageable with said cylinder to limit its forward movement toward said barrel, said frame including a wall located adjacent the rear end of said cylinder, a detent element received in said wall and having a generally spherical face which protrudes forwardly therebeyond, means defining a detent recess at the rear end of said cylinder for receiving said protruding face of said detent element, and a spring for urging said detent element forwardly into engagement with said detent recess to thereby exert a biasing force on said cylinder urging it forwardly and resiliently holding it in engagement with said stop means, said detent recess having such a shape that said detent element when urged forwardly against said recess it biases said rear end of said cylinder to a normal centered position relative to said frame and so that as a result of a lateral force applied to said rear end of said cylinder said detent element is cammed rearwardly to permit said rear end of said cylinder to move laterally under the influence of said lateral force.
12. In a firearm the combination defined in claim I1 further characterized by said stop means comprising at least in part a rearwardly facing surface on said frame which surface is en gageable with said forward end of said cylinder.
3. In a firearm the combination defined in claim ll further characterized by said means for supporting said cylinder including a crane pivotally connected to said frame and located adjacent the forward end of said cylinder, and said stop means comprising at least in part a rearwardly facing surface on said crane which surface is engageable with said forward end of