Abstract:
A revolver for firing high velocity ammunition includes a frame, a cylinder, a barrel, and a firing mechanism. The revolver may include one or more of the following, each of which is especially adapted for use in the context of firing high velocity ammunition: spacers for adjusting a barrel-cylinder gap, for eliminating broaching of the rearward surface(s) of the barrel; a forcing cone formed in the rearward opening of the barrel for accommodating deformed projectiles; a reflective surface (e.g., mirrored surface) provided on the cone and/or barrel rearward surfaces, for reducing erosion resulting from using high velocity ammunition; gain-twist rifling in the barrel for a smoother transition to full projectile velocity; a larger diameter, hardened firing pin bushing for minimizing brass flow in the rearward direction; and a front sight assembly that minimizes lateral shift or drift of the sight pin during firing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 60/627,491, filed Nov. 12, 2004; and U.S. Utility application Ser. No. 11/270,944, filed Nov. 10, 2005, both of the foregoing hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to firearms and, more particularly, to revolvers having modified structures that are adapted for the firing of high velocity ammunition. 
       BACKGROUND OF THE INVENTION 
       [0003]    High velocity ammunition is well known for use in rifles and other long guns. Ammunition of this type is characterized by muzzle velocities in excess of 2,500 feet per second (fps). Handguns, however, have not been capable of muzzle velocities of this magnitude, and have an upper bound of about 1,500 fps. Revolvers present the added challenge of a barrel-cylinder (BC) gap to allow for cylinder rotation. In such revolvers, the hot gases generated by the ignition of the powder are vented out the cylinder and down the barrel, with some venting at the BC gap, with a concomitant loss of pressure and bullet velocity. The BC gap must be established and uniformly maintained between the forward-most surface of the chamber and the rearward-most surface of the barrel to ensure that proper cylinder pressures are maintained during firing. In revolvers in which the barrels are threaded to the frame so as to extend through a rearward-facing portion of the frame, methods for setting the BC gap include broaching the rearward surface of the barrel after the barrel is threaded into the frame. This broaching method produces tool marks on the end surface of the barrel adjacent the cylinder and oftentimes mars the finish of the barrel. 
         [0004]    The use of high velocity ammunition causes a more powerful and intense release of the high-pressure gases from the cartridge casings upon firing. Correspondingly, a greater acceleration of the bullet from the cartridge is realized with the projectile traveling from the cylinder across the BC gap to the barrel. The greater force necessary to achieve muzzle velocities in the range of 2,500 fps generates forces of a magnitude that can cause cartridge brass to flow in a rearward direction and somewhat increased bullet deformation. Standard geometries at the rearward end of the barrel (at which the bullet enters) include tapered or chamfered surfaces to facilitate the engagement of the deformed projectile. Standard constant twist rifling allows the projectile to be sufficiently engaged and longitudinally rotated at a constant rate as the projectile traverses the length of the barrel. 
         [0005]    Certain high-powered revolvers have a shroud placed over the barrel and can therefore have a releasably secured sight assembly mounted at the forward end of the shroud. Such sight assemblies usually employ known mounting arrangements to ensure proper sight alignment and positive sight retention. These replaceable sight assemblies generally comprise sights with a dovetail base that are urged by springs in the forward direction such that forward edges of the sights engage laterally-positioned mounting pins. With this releasable sight configuration, there sometimes is displayed an undesirable lateral shift or drift of the laterally-positioned pin due to the forces associated with high velocity ammunition. In such cases, the sights correspondingly shift with the laterally-positioned mounting pins. 
         [0006]    What is needed is a revolver firearm that is capable of reliably firing high velocity ammunition and that addresses these and other special circumstances found with operating a handgun in this extreme range of muzzle velocities. 
       SUMMARY OF THE INVENTION 
       [0007]    An embodiment of the present invention relates to a firearm for firing high velocity ammunition, provided in the form of a revolver that includes a frame, a cylinder, a firing mechanism, and a barrel, all of which are operably interconnected in a manner similar to a standard revolver. For example, the cylinder is pivotally mounted in the frame and includes a plurality of chambers configured to receive and align cartridges with the barrel, while the firing mechanism includes a trigger and a hammer, wherein upon a user pressing the trigger in a rearward direction, the hammer is operated to discharge a cartridge loaded into one of the chambers. 
         [0008]    One advantage of the revolver of the present invention is that a space between a rearward portion of the barrel and a forward surface of the cylinder can be adjusted longitudinally within a shroud housing the barrel from a forward end of the barrel. Such adjustment is typically effected by the use of one or more spacers. By allowing the position of the barrel to be adjusted in such a manner, the need to broach the rearward surfaces of the barrel is eliminated. 
         [0009]    Another advantage is that the barrel is provided with a forcing cone integrally formed at the rearward opening thereof. The forcing cone (and/or the rear surface of the barrel) can be polished or otherwise finished to provide a reflective surface that reduces the amount of erosion that can result from using the revolver with high velocity ammunition. Thus, because the surface of the cone is subject to less erosion, the barrel life of the handgun can be extended. Furthermore, the geometry of the surface of the cone in conjunction with the reflective finish allows the projectile of the high velocity ammunition to show a smoother translation across the BC gap, thereby showing improved performance results in the revolver. 
         [0010]    Another advantage of the present invention is the use of gain-twist rifling in the barrel that allows for a more gradual engagement of the high velocity projectile with the rifling and further allows for a smoother transition to the full velocity of the projectile as the projectile exits the barrel. Moreover, by using a preferred electrochemical process to produce the rifling, variations in land width and profile, as well as a smoother transition to the full twist rate, can be realized. 
         [0011]    Yet another advantage of the present invention is the optional provision of a larger diameter, hardened firing pin bushing that allows for improved support at the head of the cartridge casing. By utilizing a larger bushing (e.g., a bushing in which the diameter thereof is at least as large as the casing head), brass flow in the rearward direction may be minimized when high velocity ammunition is fired. 
         [0012]    Still another advantage of the present invention is an interchangeable front sight assembly with a lateral locating pin having a dumbbell-shaped configuration. Such a configuration minimizes lateral shift or drift of the sight pin during the firing of high velocity ammunition from the handgun. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0013]      FIG. 1  is a simplified schematic representation of a handgun made in accordance with the present invention. 
           [0014]      FIG. 2  is a perspective view of a cylinder and ejector of the handgun of  FIG. 1 . 
           [0015]      FIG. 3  is a simplified schematic representation of the handgun of  FIG. 1  in exploded cutaway view. 
           [0016]      FIGS. 4 ,  4 A, and  5  are simplified schematic representations of the handgun of  FIG. 1  in cutaway view. 
           [0017]      FIG. 6  is a simplified schematic representation of a barrel of the handgun of  FIG. 1  showing a forcing cone. 
           [0018]      FIG. 7  is a simplified schematic representation of a barrel of the handgun of  FIG. 1  showing gain-twist rifling. 
           [0019]      FIG. 8  is a perspective view of a portion of a frame of the handgun of  FIG. 1 . 
           [0020]      FIG. 9  is a perspective view of the frame of the handgun of  FIG. 8  showing a firing pin bushing mounted in a yoke of the frame. 
           [0021]      FIG. 10  is a perspective view of the firing pin bushing of the handgun of  FIG. 9  mounted in the yoke of the frame and shown in cutaway view. 
           [0022]      FIGS. 11 and 12  are perspective views of the firing pin bushing for a revolver made in accordance with the present invention. 
           [0023]      FIG. 13  is a side elevation view of the frame and firing pin bushing of  FIG. 9 . 
           [0024]      FIG. 14  is a side elevation view of a front sight assembly on the forward end of the barrel of a revolver made in accordance with the present invention. 
           [0025]      FIG. 15  is a perspective view of the front sight assembly of  FIG. 14 . 
           [0026]      FIGS. 16 and 17  are perspective and side elevation cross-section views, respectively, of a bushing-less, hardened frame according to an alternative embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    Referring to  FIG. 1 , one exemplary embodiment of a firearm incorporating the present invention is shown generally at  10  and is hereinafter referred to as “firearm  10 .” The firearm  10  is preferably a revolver (as described in U.S. Pat. Nos. 6,330,761 and 6,523,294, which are incorporated herein by reference) that includes a frame  12 , a cylinder  14 , a firing mechanism  16 , and a barrel  18 . A firing axis  19  extends coaxially with the barrel  18 . High velocity ammunition is the preferred type of ammunition for use in the firearm  10 , such ammunition typically being capable of attaining bullet muzzle velocities of about 2,500 feet per second or greater. 
         [0028]    The cylinder  14  is pivotally mounted in the frame  12  and includes an ejector  20 , a ratchet  22 , and a plurality of chambers, two of which are shown at  26 . The chambers  26  are configured to receive and align cartridges with the barrel  18 . The cylinder  14  is pivotally mounted on a yoke  28  that is attached to the frame  12 . A top strap  29  extends across a top portion of the frame  12  from a forward portion to a rearward portion to define a generally rectangular aperture. When the cylinder  14  is closed with respect to the yoke  28 , the cylinder  14  is positioned in the rectangular aperture such that a chamber  26  of the cylinder  14  is longitudinally aligned with the barrel  18 . A retaining mechanism  30  maintains the cylinder  14  within the rectangular aperture. A cylinder release bar actuated by a thumb piece  36  allows the cylinder  14  to be rotated out of the rectangular aperture into a cylinder-open position. 
         [0029]    The firing mechanism  16  includes a trigger  40  and a hammer  42 . Upon a user pressing the trigger  40  in a rearward direction, the hammer  42  is operated to discharge a cartridge loaded into the firearm  10 . 
         [0030]    Referring now to  FIG. 2 , the ejector  20  includes a rod  21  about which the cylinder  14  rotates. The ratchet  22  is attached at a rearward end of the rod  21  and has a plurality of detent or cut out portions  25  that correspond to the respective rearward edges of each chamber  26 . The ratchet  22  is dimensioned such that it is received in a recess at the rear surface of the cylinder  14  so as not to obstruct the rotation of the cylinder  14  on the yoke  28  or the opening and closing of the cylinder  14  in the rectangular aperture. Upon loading a cartridge into any chamber  26 , a rim on a base of the casing of the cartridge engages the cut out portion  25  of the ratchet  22 . To eject cartridges from the cylinder  14 , the firearm is placed in the cylinder-open position and a forward end of the rod  21  is urged in the rearward direction. The defining edges of each cut out portion  25  engage the rims of the casings, and the casings are pulled out of the rear of the cylinder  14 . 
         [0031]    Referring now to  FIGS. 3-5 , the barrel  18  is mounted in a shroud  44  attached to a forward portion of the frame  12 . (The shroud  44  may be considered part of the frame  12 , i.e., part of the support structure of the firearm.) The barrel  18  comprises an elongated, substantially cylindrical member having a cylindrical bore  46  extending longitudinally there through. The surfaces of the barrel  18 , namely, the rearward-most edge surface at which the projectile enters the barrel and the wall of the cylindrical bore  46 , are polished or otherwise finished to provide a reflective surface such that the hot gases generated during the firing of ammunition are less likely to have an effect on the barrel surfaces. For example, the reflective surface may be a highly reflective surface (by which it is meant a surface with a reflectance or albedo of at least 0.85) or a mirrored surface (a reflectance/albedo of at least 0.95). Upon assembly of the revolver, the cylindrical bore  46  registers with the respective chambers  26  of the cylinder  14  and forms the longitudinal firing axis  19 . 
         [0032]    The clearance between the forward-most surface of the cylinder  14  and the rearward-most surface of the barrel  18  is the barrel-cylinder (BC) gap. The barrel  18  is mounted in the shroud  44  using a spacer  48  positioned at a forward end of the barrel  18  to give the desired BC gap (see  FIG. 4A  for a detail view). The spacer  48 , which may be annular-shaped, washer like device, is positioned against a flange  50  on the shroud  44 . The fore end of the barrel  18  may also be provided with a flange  51  for abutting the spacer  48  when the firearm  10  is assembled. Alternatively, the spacer  48  may be removably connected to the barrel in a standard manner. The width of the spacer  48  is selected to give the desired BC gap. Alternatively, two or more spacers  48  can be stacked together on the barrel  18  to adjust the BC gap. Thus, because the BC gap is adjusted via the spacer(s)  48 , the threading of the barrel into the frame and the broaching operation in which the rearward portion of the barrel is cut off (potentially marring the polished barrel surface) is avoided. A muzzle brake  52  ( FIG. 5 ) fits over the forward end of the barrel  18  and is positioned in the shroud  44 . The muzzle brake  52  is held in the shroud  44  using a screw  54  or similar device. 
         [0033]    Referring now to  FIG. 6 , a forcing cone  60  is integrally formed with the barrel  18  at the rearward opening thereof. The forcing cone  60 , which accommodates for the deformation of the projectile as the projectile traverses the BC gap, comprises a rearward edge  62  that is defined by the perimeter of the rearward opening of the barrel  18 . The forcing cone  60  extends radially inward toward the firing axis  19  to terminate at the inner wall  64  of the barrel  18 . Thus, the forcing cone  60  has a slightly larger entry diameter as compared to the central bore diameter of the barrel  18 , thereby providing a clearance between the cylinder and the barrel  18  to facilitate movement of a projectile (e.g., bullet) from the cylinder to the barrel  18 . In particular, the slightly larger entry diameter of the forcing cone  60  enables the projectile to enter the barrel  18  with a reduced probability that the projectile will engage a rearward-facing surface  66  of the barrel  18 . 
         [0034]    The rearward edge  62  of the forcing cone  60  is configured to have a radius (e.g., it is rounded) to further facilitate the movement of the projectile from the cylinder into the forcing cone  60 . A forward edge  68  of the forcing cone  60  may be likewise configured to have a radius to even further facilitate the movement of the projectile from the forcing cone  60  to the barrel  18 . A wall  70  of the forcing cone  60  adjacent the rearward edge  62  may be provided with a reflective finish (e.g., a highly reflective or mirrored surface) to allow hot gases to flow more smoothly and to reduce the opportunity for the surface of the forcing cone  60  to erode. 
         [0035]    Referring now to  FIG. 7 , lands  74  and grooves  76  are disposed on an inner wall  78  of the cylindrical bore  46  of the barrel  18  to form gain-twist rifling. Gain-twist rifling is characterized by a twist rate (turns per unit distance) that varies along the length of the barrel from a slow twist at the breech/rear end of the barrel to a tighter twist at the muzzle/fore end of the barrel, e.g., from a slow rate such as one twist per 100 inches to a higher rate such as one twist per 20 inches. The gain-twist rifling of the present invention may be produced on the inner wall  78  using an electrochemical process that produces rifling in which the width of the lands  74  increases as the twist rate increases, thereby allowing more of the bullet surface to be engraved as the bullet traverses the length of the barrel  18 . Essentially, as the lands get wider, the bullet is gripped tighter as it spins faster. This is different from conventional grain-twist rifling, where the full land and groove profiles are engraved initially, and then the twist rate is increased. One exemplary electrochemical process for producing rifling in gun barrels is disclosed in U.S. Pat. No. 5,819,400, which is incorporated herein by reference in its entirety. Gain-twist rifling lessens the abrupt transition from zero angular velocity to the nominal or maximum angular velocity. The smoother transition up to the nominal or maximum angular velocity has been found to increase accuracy by minimizing bullet deformation as it engraves the rifling. Furthermore, users may feel less recoil torque because of the bullets&#39; smoother transition to maximum angular velocity. 
         [0036]    As noted, the lands  74  closest to the breech end of the barrel (near the forcing cone  60 ) may be smaller in width. The edges of these lands will typically not be as sharp as those of the lands further down the barrel where the twist rate is increased. In particular, the edges of the lands proximate to the forcing cone may be provided with smoother or more rounded edges, as a result of the electrochemical process or otherwise. This results in a reduction of bore erosion ahead of the forcing cone. 
         [0037]    Referring now to  FIGS. 8-13 , the firearm also incorporates a firing pin bushing  80  having a diameter (or other widest dimension if the bushing is non-circular) that meets or exceeds the diameter of the head of the cartridge casing used in the handgun. As is shown in  FIG. 8 , the firing pin bushing  80  is mounted in a recess  82  in a forward-facing, bolster face portion  81  of the frame  12 . The recess  82  is defined by a first vertical surface  84 , a first land  86 , a second vertical surface  88 , and a second land  90 . A chamfered rim  89  defines the edge between the first land  86  and the second vertical surface  88 . The lands and vertical surfaces of the recess  82  are sufficient to accommodate the firing pin bushing  80  with a degree of precision such that the firing pin bushing  80  can be mounted with a minimum amount of angular displacement from the flush surface of the bolster face  81  at the upper portion thereof. Referring to  FIG. 9 , a lower portion of the firing pin bushing  80  extends into a cavity or recess  91  in the bolster face  81 . 
         [0038]    Referring now to  FIGS. 11-13 , the firing pin bushing  80  comprises a primary member  92  having a planar front face  94 , a firing pin aperture  96  drilled, bored, machined, cast, or otherwise formed in the center of the primary member  92  so as to extend therethrough, and a seating member  98  extending from a rearward face  100  of the primary member  92 . The primary member  92  may be disc- or plate-shaped, i.e., shaped akin to a washer or squat cylinder, and the seating member  98  is preferably generally cylindrical in shape and concentrically positioned relative to the firing pin aperture  96 . 
         [0039]    The width dimension of the front face  94  is at least as great as the diameter of a cartridge casing head used in the firearm to prevent brass flow during the use of high-pressure ammunition. As can be best seen in  FIGS. 11 and 13 , the perimeter of the front face  94  has a radius, i.e., its outer edge is rounded. The perimeter of the rearward face  100  ( FIGS. 12 and 13 ) is chamfered to facilitate the insertion of the firing pin bushing  80  into the recess. A transition surface  104  between the rearward face  100  and the outer wall of the seating member  98  is concavely radiused to provide a space between the chamfered rim  89  and the firing pin bushing  80 . The rearward-most edge of the seating member  98  is chamfered at an angle of about 30 degrees to even further facilitate the insertion of the firing pin bushing  80  into the recess. As can best be seen in  FIG. 13 , the diameter of the aperture of the seating member  98  is greater than the diameter of the firing pin aperture. The aperture of the seating member  98  registers with a bore  108  in the yoke  28  through which the firing pin (not shown) translates to extend through the firing pin aperture  96  to engage a cartridge. 
         [0040]    Referring to  FIG. 14 , the firearm incorporates a front sight assembly  120  that is mountable into the shroud  44 . The sight assembly  120  of the present invention is an improvement on the sight assembly of U.S. Pat. No. 5,802,757, which is incorporated herein by reference in its entirety. The sight assembly  120  of the present invention includes a sight  123  having a sight pin portion  121  and an anchor portion  122 . The anchor  122  is attached to or connected to the sight pin  121  via a connector  124 , which is of a lesser width-wise dimension than either the sight pin  121  or the anchor  122 . The anchor  122  is received in a slot  126  on the uppermost surface of the forward portion of the shroud  44 . The anchor  122  and the receiving slot  126  extend longitudinally in the direction of the longitudinal firing axis of the firearm. In mounting the sight  123 , the anchor  122  is press-fitted into the receiving slot  126  such that the connector  124  and the anchor  122  engage a laterally mounted dumbbell-shaped pin  125  that is positioned across the receiving slot  126  perpendicular to the direction in which the slot  126  and the longitudinal firing axis extend. A spring  130  mounted in the rearward portion of the receiving slot  126  is configured to urge the anchor  122  (and, accordingly, the connector  124  and the sight  121 ) in a forward direction against the dumbbell-shaped pin  125 . 
         [0041]    Referring now to  FIG. 15 , the dumbbell-shaped pin  125  comprises a dowel-shaped connection member  131 , a first protrusion  132  attached to a first end of the connection member  131 , and a second protrusion  134  attached to a second end of the connection member  131 . A forward surface of the connector is substantially vertical and perpendicular to the longitudinal firing axis when the sight  123  is mounted in the shroud. A forward surface of the anchor  122  is tapered such that when the connector  124  and the anchor  122  are attached to each other or integrally formed, an angle A is defined. Upon urging the anchor  122  and the connector  124  against the dumbbell-shaped pin  125 , the dowel-shaped connection member  131  is received in a vertex of the angle A. The first protrusion  132  and the second protrusion  134  capture the anchor  122  and the connector  124  there between, thereby facilitating the retention of the sight assembly  120  in place. 
         [0042]      FIGS. 16 and 17  show a “bushing-less” frame  140  according to an alternative embodiment of the present invention. The frame  140  is not provided with an enlarged firing pin bushing  80  (as shown in  FIGS. 8-13 ) or other type of firing pin bushing. Instead, the frame  140  has a firing pin aperture  142  formed directly in the frame and extending there through, and the area  144  of the frame around the aperture (e.g., the bolster face  81 ) is hardened using standard methods. Optionally, the entire frame  140  may be hardened. As should be appreciated, traditional firing pin bushings present a “seam” in the bolster face proximate the casing head, as between the bushing and frame. With high velocity ammunition, the brass casing may start to flow into the seam, jamming the cylinder. With the enlarged bushing  80 , the seam is moved away from the casing head. With the bushing-less frame  140 , the seam is eliminated entirely. 
         [0043]    Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the above disclosure.