Abstract:
A laser precision bore sight assembly and method aligns a laser beam along the longitudinal axis of a gun barrel. At the proximate end of an elongated bore shaft is rotatably mounted a compressible barrel insert with a continuous outer surface which resiliently engages the inside wall of the gun barrel to coaxially align the longitudinal axis of the proximate end of the shaft with the longitudinal axis of the gun barrel. The exterior surface of an alignment cone is provided on the distal end of the bore shaft. A battery/switch housing, containing a switch assembly, cooperates with a laser housing assembly to provide an enclosure for a battery. A laser source in the laser housing assembly provides a laser beam in a direction coaxial with the longitudinal axis of the shaft. Matching threads provide for relative longitudinal movement such that a terminal of the battery engages the switch assembly to activate the laser source. The compressible barrel-shaped insert is a cylinder formed of a machined acetal material. Different sizes of compressible barrel inserts are provided for different gun-barrel calibers. A three point laser alignment mechanism directs the laser beam along the longitudinal axes of the shaft and the bore of the gun barrel, even when the shaft is rotated. The invention also provides a method for aligning a laser beam along the longitudinal axis of the bore of a gun barrel.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to techniques for calibration of gun sights and, more particularly, to a laser precision bore sight assembly. 
     2. Prior Art 
     Previously, several different systems have been used for calibration of gun sights. To obtain an accurate alignment of a weapon bore sight or of a training device attached to a weapon, the first step in using a bore sight device is to rotate the bore sight device a minimum of 360 degrees to confirm that the alignment of the bore sight is concentric to the bore of the weapon. If the laser point that is projected from the bore sight device onto a target 10 meters away traces a circle on the target, then the axis of the bore sight device is not concentric with the bore of the weapon. 
     One type of alignment device, as disclosed in U.S. Pat. No. 4,825,258, uses a light source, such as a laser, which is coaxially mounted outside of the gun barrel on the outer end of a hollow cylindrical metal rod, the inner end of which extends into the bore of a gun barrel. The outer end of the hollow cylindrical rod is a larger cylinder which engages the inside wall of the gun barrel. The inner end of the hollow rod is smaller in diameter than the bore of the gun barrel and has an expandable, split end formed into a number of longitudinal metal fingers. The free ends of the longitudinal fingers are expanded outwardly using a cone-shaped mandrel which is drawn into the metal fingers with a screw which extends out through the hollow rod mechanism to force the cone-shaped mandrel into the fingers. In this manner, the ends of the metal fingers are pushed outwardly to engage the inner wall of the bore of the gun barrel. This arrangement is supposed to fix the inner end of the rod in position in the bore of the gun barrel and to maintain the axis of the rod in alignment with the axis of the bore of the gun barrel. 
     Note that, this type of a system can be rotated prior to the metal fingers engaging the walls of the gun barrel, but the fit of the fingers is too loose to maintain concentric alignment. If the metal fingers fully contact the barrel, the fingers catch upon the rifling grooves making it difficult to rotate the device while maintaining concentric alignment of a laser beam. When this arrangement is axially rotated in the gun barrel, some of the metal fingers engage the rifling grooves formed in the inside walls of the gun barrel while other metal fingers directly engage the walls of the gun barrel, which causes the inner end of a rotated rod to change its alignments in the gun barrel. The type of metal material used for the fingers also has an effect of the performance of such an arrangement. Use of a material, which is softer than the hard steel of a gun barrel, such as brass, results in wear of the metal fingers and uneven alignment of the metal fingers within the gun barrel so that the inner end of the rod does not remain coaxially aligned with the gun barrel. On the other hand, use of a harder material for the metal fingers results in wear and damage to the rifling within the gun barrel. 
     U.S. Pat. No. 5,365,669 discloses another system which uses a laser light source mounted in a cartridge-shaped housing that is contained in a cartridge chamber of a gun. This system is not adjustable and is subject to the axial offsets and misalignments between the axis of the cartridge chamber and the axis of the bore of the gun barrel. 
     What is needed is a system which maintains direct coaxial alignment of a laser light source along the axis of the bore of a gun barrel, particularly when that laser light source is axially rotated. 
     SUMMARY OF THE INVENTION 
     The present invention provides a bore sight assembly which is used for aligning optical scopes, mechanical firearm sights, laser sighting devices, firearm training systems, or other devices that are aligned with a target point, such that a projectile or a simulated projectile fired from a weapon or a training device strikes the target point. The present invention provides a precision bore sight alignment assembly which remains in coaxial alignment with the axis of the bore of a gun barrel, particularly when the rod is rotated within the gun barrel, to thoroughly maintain concentric alignment of an alignment laser beam. 
     The present invention provides a laser precision bore sight system for bore sight alignment of a laser beam along the longitudinal axis of a gun barrel. As mentioned above, this system is suitable for alignment of various types of weapon sights. This system is also suitable for simulating firing of a weapon in a training system using a laser beam to simulate the path of an actual projectile or bullet. 
     A system according to the invention includes an elongated bore shaft with a longitudinal axis. The bore shaft is adapted to having its proximate end inserted into the bore of the gun barrel. At the proximate end of the elongated shaft is rotatably mounted a compressible barrel insert which has a continuous outer surface. The barrel insert is adapted to be inserted in the gun barrel so that the outer surface thereof resiliently engages the inside wall of the gun barrel. In this way the longitudinal axis of the proximate end of the bore shaft is coaxially aligned with the longitudinal axis of the gun barrel. 
     The distal end of the bore shaft is also coaxially aligned with the axis of the gun barrel. One embodiment of the invention includes an alignment cone which is fixed to the distal end of the bore shaft. The surface of the alignment cone increases in diameter as it extends distally away from the bore shaft. Depending on the caliber of the gun, a certain area of the conical surface of the alignment cone engages the distal inner edge of the gun barrel. In this way the distal end of the shaft is aligned with the longitudinal axis of the gun barrel. 
     Coaxially mounted adjacent to the alignment cone is a battery/switch housing which contains a switch assembly. A laser housing assembly is coaxially mounted adjacent to the battery/switch housing and contains a laser subassembly having a laser source which provides a laser beam in a direction coaxial with the longitudinal axis of the shaft. The battery/switch housing and the laser housing assembly have longitudinal end bores formed therein to provide an enclosure for a battery. The battery/switch housing and the laser housing assembly also have corresponding matching threads formed thereon to provide for relative longitudinal axial movement therebetween when they are rotated with respect to each other such that a terminal of the battery engages the switch assembly to activate the laser source. 
     In one preferred embodiment of the invention, the compressible barrel insert is a cylinder formed of a machined acetal material. In one preferred embodiment, the compressible cylindrical barrel insert is rotatably mounted on the cylindrical bearing surface of a barrel insert retainer shaft which is coaxially screwed to the end of the elongated shaft. 
     To accommodate a number of gun barrel sizes, the compressible barrel insert is selected from a group of cylindrical barrel inserts, corresponding to a particular gun-barrel caliber. 
     The laser housing assembly also includes a three point laser alignment mechanism for adjusting the alignment of the laser subassembly so that the laser beam is directed along the longitudinal axes of the shaft and the bore of the gun barrel when the shaft is rotated. One preferred embodiment of the three-point alignment mechanism includes fixed adjustments made at a factory or a service station. Another preferred embodiment of the three-point alignment mechanism is manually adjustable by a user in the field and includes two manually adjustable screw mechanisms, the ends of which contacts the laser subassembly and a spring-loaded bushing, which is fixed to a set screw and which biases the laser subassembly against the first and the second manually adjustable adjustment screws. The two manual adjustment screw mechanisms each includes a fine adjustment screw which moves radially with respect to the axis of the shaft and a detent mechanism provides for stepped manual adjustment of the adjustable screws. 
     The battery/switch housing switch assembly is contained in a cavity formed in a battery/switch housing and includes a compression spring having flat ends and contained within the cavity. A cup-shaped fiber washer has a center bore formed therethrough to receive a contact pin which is a flat-head brass screw or a smooth sided pin, both with a conical head and an end contact surface. The contact pin is held in the center bore of the fiber washer with the head of the pin on one wide of the fiber washer and a nickel-plated washer on the other side of the fiber washer. A solder blob covers the top surface of the conical head to serve as a contact area for the positive terminal of a battery. The contact pin is soldered to the nickel plated washer. Relative twisting of the battery/switch housing with respect to the laser housing assembly pushes the positive battery terminal into the head of the contact pin such that the contact end of the contact pin contacts the housing to activate the laser source. 
     The barrel-shaped insert includes a cylindrical base, which is rotatably mounted to the shaft and an attached radially resilient section which resiliently positions the axis of the end of the shaft along the longitudinal axis of the gun barrel. In one preferred embodiment of the invention, the radially resilient section has a peaked cylindrical area which has a maximum diameter which is greater than the diameter of the gun barrel such that when the barrel-shaped insert is inserted into the gun barrel, the external surface of peaked cylindrical area contacts the interior wall of the gun barrel and is pushed radially inwardly to conform to the smaller diameter of the gun barrel. The peaked cylindrical area of the barrel insert snugly engages the wall of the gun barrel to precisely position the one end of the shaft within the gun barrel along the longitudinal axis of the gun barrel and the peaked cylindrical area of the barrel insert provides continuously contact with the inner wall of the gun barrel in spite of the rifling grooves formed in the gun barrel and the tough material of the barrel insert does not damage the interior surface or the rifling of the gun barrel. 
     One embodiment of the radially resilient barrel-shaped insert has a section which has an interior diameter larger than the interior diameter of the cylindrical base section and a peaked cylindrical area with a maximum diameter which is greater than the diameter of the gun barrel. 
     Another embodiment of the radially resilient section includes an integral radially outwardly extending support flange from which longitudinally extends an integral cantilevered resilient ring with a peaked cylindrical area which has a maximum diameter greater than the diameter of the gun barrel to prove a snug fit within the barrel of a gun. The integral cantilevered resilient ring is spaced apart from the main cylindrical section and has a ring-shaped space formed beneath it. 
     The three-point alignment mechanism mounted to the universal housing for adjusting the alignment of the laser subassembly includes two orthogonally aligned adjustable screw mechanisms and a spring-loaded bushing aligned for movement in a direction to bias the laser subassembly against the ends of the first and the second adjustment screws. 
     A fine adjustment retainer ring has a number of pairs of opposing internal recesses formed therein which are engaged by at least one spring-loaded ball to provide stepped adjustments. 
     The invention also provides a method for aligning a laser beam along the longitudinal axis of the bore of a gun barrel and includes the following steps: rotatably mounting a cylindrical barrel insert, which has a flexible outer cylindrical surface, to one end of a shaft having a longitudinal axis; inserting the cylindrical barrel insert into the bore of the gun barrel having a longitudinal axis and engaging the inside wall of the gun barrel bore with the outer cylindrical surface of the cylindrical barrel insert; engaging an alignment cone located at the outer end of the shaft with the outer inside edge of the gun barrel such that the longitudinal axis of the shaft is coaxially aligned with the longitudinal axis of the gun barrel when the shaft is inserted and rotated in the gun barrel; mounting a laser housing, which contains a laser source assembly, to the outer end of the shaft; directing a laser beam from the laser source assembly in a direction coaxial with the longitudinal axis of the shaft; and adjusting a three point laser alignment mechanism mounted to the universal housing for adjusting and truing the alignment of the laser beam along the longitudinal axes of the shaft and the bore of the gun barrel, even when the shaft is rotated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a laser precision bore sight assembly for insertion into the end of a gun barrel and for alignment of a laser beam along the axis of the gun barrel. 
     FIG. 2 is a partially sectional view of a section of a gun barrel with a laser precision bore sight assembly barrel according to the invention inserted therein. 
     FIGS. 3 is an exploded view showing a bore sight assembly shaft, into the end of which is inserted a retainer screw on which is axially mounted for rotation a selected one of a number of illustrated barrel inserts, each corresponding to a particular gun-barrel caliber. 
     FIG. 4A is an enlarged perspective view of one type of typical barrel insert for use with a smaller caliber gun, such as a 0.270 caliber or 7 mm. 
     FIG. 4B is an enlarged sectional view of the barrel insert of FIG.  4 A. 
     FIG. 4C is a cross sectional view of the barrel insert of FIG.  4 A. 
     FIG. 5A is an enlarged perspective view of another type of typical barrel insert for use with a larger caliber gun barrel, such as a 0.50 caliber. 
     FIG. 5B is an enlarged sectional view of the barrel insert of FIG.  5 A. 
     FIG. 5C is a cross sectional view of the barrel insert of FIG.  5 A. 
     FIG. 6A is an end view of an alternative metal spring barrel insert for a small caliber gun. 
     FIG. 6B is a partially sectional view of the alternative metal spring barrel insert FIG.  6 A. 
     FIG. 7 is an exploded, perspective view of a laser precision bore sight assembly according to the invention. 
     FIG. 8 is a sectional view showing a battery/switch housing with a battery switch assembled therein which is actuated by rotating the battery switch housing with respect to the laser housing so as push a battery terminal against one end of a contact pin so that the other end of the contact pin contacts the housing to complete the battery circuit to the laser source. 
     FIG. 9 is an exploded view showing the battery/switch housing and the battery switch components. 
     FIG. 10 is a perspective view of a laser housing. 
     FIG. 11 is an exploded end view showing a laser housing along with a fixed set screw and two adjustable windage/elevation assemblies. 
     FIG. 12 is an exploded, partially sectional view of an adjustable windage/elevation assembly. 
     FIG. 13 is a perspective view of an adjustment screw for the windage/elevation assembly of FIG.  12 . 
     FIG. 14 is a perspective view of a cap for the windage/elevation assembly of FIG.  12 . 
     FIG. 15A is a perspective view of a bonnet for the windage/elevation assembly of FIG.  12 . 
     FIG. 15B is a sectional, perspective view of the bonnet, taken along section line  15 B— 15 B of FIG. 15A, for the windage/elevation adjustment assembly of FIG.  15 A. 
     FIG. 16 is a perspective view of a retainer ring which provides fine adjustment steps for the windage/elevation adjustment assembly of FIG.  12 . 
     FIG. 17 is a plan view of a base for the windage/elevation assembly of FIG.  12 . 
     FIG. 18 is a cross sectional view of the laser housing showing a fixed adjustment assembly, which includes a bushing, a spring, and a set screw for biasing a laser module against a pair of adjustable windage/elevation assemblies. 
     FIG. 19 is an exploded, perspective view of a laser module subassembly. 
     FIG. 20 is an assembled sectional view of the laser module subassembly of FIG.  19 . 
     FIG. 21 is a sectional view of laser housing with a showing two windage/elevation adjustment assemblies and a spring loaded bushing for alignment of a laser beam from a laser housing assembly. 
     FIG. 22 is a sectional view, taken along section line  22 — 22  of FIG. 21, of a laser housing containing a laser assembly, having a windage/elevation adjustment assembly and a spring loaded bushing. 
     FIG. 23 is an exploded, partially sectional view of a front cap and lens. 
     FIG. 24 is a sectional view of an assembled front cap and lens. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it should be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which are included within the spirit and scope of the invention as defined by the appended claims. 
     FIGS. 1 and 2 illustrate a laser precision bore sight assembly  10  for insertion into the bore  12  of a gun barrel  14 , of, for example, a rifle pistol, or shotgun for alignment of the gun sights. The laser precision bore sight assembly  10  includes a rotatable barrel insert  15  which is mounted on the proximate end of a bore shaft  16  and inserted into the gun barrel. At the distal end of the shaft  16  are coaxially attached a series of elements aligned along a longitudinal axis. These elements include an alignment cone  18 , a coaxial battery/switch housing  20 , and a coaxial laser housing  22 . The function of the laser precision bore sight assembly  10  is to provide a laser beam  23  which is aligned with the longitudinal axis of the gun barrel. 
     The length of the bore shaft  16  is optionally long or short depending upon whether it is used with a rifle or a pistol. A proximate end  24  of the bore shaft  16  has the rotatable barrel insert  15  mounted thereto. The proximate end of the shaft  16  is inserted into the bore  12  of the gun barrel  14  to align the proximate end of the laser precision bore sight assembly  10  along the axis of the gun barrel. The distal end  26  of the bore shaft  16  is attached to the alignment cone by being press fit into a bore formed through a smaller end face of the alignment cone  18 . The coaxial alignment cone  18  is a truncated cone which increases in diameter as it extends away from the smaller proximate end face to terminate in a larger distal end. 
     FIG. 2 illustrates that the conical surface of the coaxial alignment cone  18  is adapted to engage the inside edge of the bore  12  of the gun barrel in order to longitudinally position the distal end of the bore shaft  16  along the axis of the gun barrel. For each barrel diameter, somewhere along the alignment cone  18  is a circumference which matches the circumference of the inside edge of the gun barrel to concentrically align the distal end of the shaft with the longitudinal axis of the gun barrel. 
     FIG. 3 illustrates that the proximate end  24  of the bore shaft  16  has an axial bore  30  which extends 0.060 inches into the end of the bore shaft. A smooth interior surface  31  is followed by a threaded countersink interior, which accommodates external threads  32  formed at one end of a coaxial barrel insert retainer shaft  34 . The barrel insert retainer shaft  34  has a smooth external surface  33 , which is approximately 0.04 inches in length and which is located adjacent to and inboard of the threads  32 . When the external threads of the retainer shaft  34  are screwed into the internal threads in the end of the bore shaft  15 , the surface  33  slip fits inside the surface  31 , with the surfaces overlapping about approximately 0.040 inches to maintain axial alignment of the two shafts. The tolerances on the diameters of the overlapping surfaces  31 ,  33  are tightly held to create a very close slip fit therebetween. This helps to lock the retainer shaft  34  to the bore shaft  16  so that the retainer shaft  34  will not back out if the bore sight assembly  10  is counter rotated in the gun barrel. 
     The barrel insert retainer shaft  34  has an external cylindrical bearing surface  36 . The diameter of the bearing surface  36  is smaller than the diameter of the bore shaft  16  to provide a step or shoulder therebetween. These shoulders hold the rotatable barrel insert  15  in position on the shaft  34 . 
     FIG. 3 also illustrates a number of cylindrical barrel inserts  41 - 47  each of which is rotatably mountable on the smaller cylindrical bearing surface of the barrel insert retainer shaft  34  between the steps or shoulders formed by the larger shaft  16  and the larger end portion  38  of the barrel insert retainer shaft  34 . The space between the shoulders allows the barrel insert to freely rotate with the rifling in a gun barrel to facilitate insertion of the barrel insert  15  into the gun barrel and to prevent the sharp edges of the barrel rifling from shaving off bits of the barrel insert. Each one of the cylindrical barrel inserts  41 - 47  corresponds to a particular gun-barrel caliber. Barrel insert  41  is used for a 0.22 caliber, 0.223 caliber, or 5.36 mm. gun barrel. Barrel insert  42  is used for a, which extends 0.270 caliber or 7 mm. gun barrel. Barrel insert  43  is used for a 0.30, 3006, 308, or 7.62 mm. gun barrel. Barrel insert  44  is used for a 0.38 caliber, 0.357 caliber, or 9 mm. gun barrel. Barrel insert  45  is used for a 0.40 caliber or 10 mm. gun barrel. Barrel insert  46  is used for a 0.44 caliber or 0.45 caliber gun barrel. Barrel insert  47  is used for a 0.50 caliber gun barrel. 
     The barrel inserts  41 - 47  are precision machined from a black acetal material. Acetal material, trademarked a Delrin®, is a crystalline thermoplastic polymer with a high melting point which provides a high modulus of elasticity combined with great strength, stiffness and resistance to abrasion. It provides dimensional stability for fabrication of close tolerance items. It has a low coefficient of friction, excellent machinability, good impact and abrasion resistance, and natural lubricity. The barrel inserts are machined from this flexible, resilient, tough, durable material. Acetal provides good slip characteristics over the steel material of a gun barrel without being deformed or marring the gun barrel or rifling. The barrel inserts are slightly oversized to accommodate worn, oversized gun barrels. 
     Instead of using the cylindrical barrel insert  41  for a 0.22, 0.223, or 5.56 mm. gun barrel, external threads  50  of an alternative metal spring barrel insert  52  are threaded into the internally threaded bore  30  of the shaft  16 . 
     FIG. 4A, FIG.  4 B and FIG. 4C illustrate in greater detail an exemplary embodiment of one type of typical barrel insert  42  for a smaller caliber gun barrel, such as a 0.270 caliber or 7 mm. gun barrel. The barrel insert  42  has two integral coaxial cylindrical symmetric sections, including a cylindrical base  60  and an attached radially resilient end section  62 . The cylindrical base  60  rotatably mounts the barrel insert  42  to the end of the shaft  16  while the attached radially resilient end section  62  resiliently positions the axis of the end of the shaft  16  coaxially along the longitudinal axis of the gun barrel. 
     For this exemplary embodiment of a barrel insert, the cylindrical base  60  has a central bore  66  formed therein with an internal diameter D 1  of 0.148+001−0.000 inches. To provide precision rotation of the barrel insert  42  around the retainer shaft  34 , the interior wall defined by the central bore  66  in the section  60  engages the bearing surface  36  of the barrel insert retainer shaft  34 , where the bearing surface  6  of the retainer shaft has a diameter of 0.148+/−0.0005 inches. The smaller external diameter D 2  of the base section  60  is 0.246 inches to accommodate the 0.270 inch diameter of the gun barrel bore. 
     The external diameter of the radially resilient end section  62  increases from the 0.246 inches of the external diameter D 2  of the base  60  to a peaked cylindrical ridge area  64  which has a maximum diameter D 3  of 0.274 inches. The external diameter of the radially resilient end section  62  then tapers back down to a diameter D 5 , which is the same as the smaller diameter D 2  of the base  60 . The outer end of the resilient end section  62  has an internal bore  70  formed approximately half way through with a diameter D 4  of 0.160 inches. The inner portion of the end section  64  has an internal bore formed therein which decreases in diameter from diameter D 4  to diameter D 1 . 
     When the barrel insert  42  is positioned in the gun barrel for rotation about the longitudinal axis of the barrel insert retainer shaft  16 , the interior walls of the main cylindrical section  60  of the barrel insert  42  snugly engage the cylindrical bearing surface  36  of the barrel insert retainer shaft  34  to provide precise rotation of the barrel insert  42 . Note that the interior surface of the bores in the end section  64  do not engage the bearing surface  36  of the barrel insert retainer shaft  16 . 
     When the barrel insert  42  is inserted into the 0.270 diameter gun barrel, the external surface of peaked cylindrical ridge area  64  with the maximum diameter D 3  of 0.274 inches contacts the wall of the gun barrel and is pushed radially inwardly to conform to the smaller 0.270 diameter of the gun barrel. In this manner, the external contact area of the peaked cylindrical ridge area  64  of the barrel insert  42  snugly engages the wall of the gun barrel to precisely coaxially position the one end  24  of the shaft  16  within the gun barrel  14  along the longitudinal axis of the gun barrel. 
     The smooth cylindrical surface of the peaked cylindrical ridge area  64  of the barrel insert  42  provides continuous contact with the inner wall of the gun barrel in spite of the rifling grooves formed in the gun barrel. The tough black acetal material of the barrel insert  42  does not damage the interior surface or the rifling of the gun barrel. 
     FIG. 5A, FIG.  5 B and FIG. 5C illustrate in greater detail another embodiment of a barrel insert for a larger caliber gun, i.e., the barrel insert  47  for a 0.50 caliber gun barrel. The barrel insert  47  includes two cylindrically symmetric, coaxial, and partially concentric sections including a main cylindrical section  80  with smaller internal and external diameters and a radially resilient cantilevered section  82  with larger internal and external diameters. The main cylindrical section  80  has a central bore  86  formed there through with an internal diameter D 10  of 0.148+001−0.000 inches to provide precision rotation of the barrel insert  47  around the retainer shaft  34 . The interior wall defined by the central bore  86  in the section  80  engages the bearing surface  36  of the barrel insert retainer shaft  34 , where the bearing surface  34  of the retainer shaft has a diameter of 0.148+/−0.005 inches. The external diameter D 11  of the main cylindrical section  80  is 0.246 inches to clear the wall of a 0.500 caliber gun barrel. 
     The radially resilient cantilevered section  82  is formed integral with the main cylindrical section  80  and includes an integral radially outwardly extending support flange section  84  from which longitudinally extends an integral cantilevered resilient ring  86 . The support flange  84  has an outside diameter which steadily increases from the external diameter D 11  to a diameter D 12  which is 0.470 inches. The integral cantilevered resilient ring  86  increases in diameter to a peaked cylindrical ridge area  88  which has a maximum diameter D 13  of 0.502 inches. The external diameter of the integral cantilevered resilient ring  86  then tapers back down to a diameter D 14 , which is the same as D 12 . The integral cantilevered resilient ring  86  is spaced apart from the main cylindrical section  80  by having a ring-shaped open space  87  formed beneath it to allow the cantilevered resilient ring  82  to flex inwardly. 
     When the barrel insert  47  is guided into a 0.500 diameter gun barrel, the external surface of peaked cylindrical ridge area  88  with the maximum diameter D 13  of 0.502 inches contacts the wall of the gun barrel and is pushed radially inwardly to conform to the smaller 0.500 diameter of the gun barrel. In this manner the external contact area of the peaked cylindrical ridge area  88  of the barrel insert  47  snugly engages the wall of the gun barrel to precisely position the proximate end  24  of the shaft  16  within the gun barrel  14  along the longitudinal axis of the gun barrel. The smooth cylindrical shape of the barrel insert peaked cylindrical ridge area  88  provides smooth contact with the inner wall of the gun barrel in spite of the rifling grooves formed in the gun barrel. The tough material of the barrel insert  47  does not damage the interior surface or the rifling of the gun barrel. 
     FIG.  6 A and FIG. 6B illustrate an alternative metal spring barrel insert  52  for a gun having a small caliber such as a 0.22, 0.223, or 5.56 mm caliber. The spring barrel insert  52  is formed of a rod-shaped body having a diameter of 0.210 inches. External threads  100  are formed at one end of the spring barrel insert  52  for engagement with the internal threads of the bore  30  formed in the one end  24  of the shaft  16 . A longitudinal bore  102  is formed through the other end of the spring barrel insert  52  and three evenly spaced longitudinal slots  104 ,  105 ,  106  are formed along part of the length of the spring barrel insert to provide flexible longitudinally extending prongs  108 ,  109 ,  110 . A 0.093 chrome-plated ball  112  is pressed between the prongs to expand the prongs to fit within the barrel of a 0.22, 0.223, or 5.56 mm caliber gun. 
     FIG. 7 illustrates the various components assembled on the distal end  26  of the shaft  16  of the laser precision bore sight assembly  10 . A bore in the narrow end of the coaxial alignment cone  18  is press fit onto the end of the shaft  16 , where the coaxial alignment cone  18  provides for coaxial alignment of the distal end of the shaft  16  with the distal end of various different caliber gun barrels. 
     The other larger, distal end of the coaxial cone  18  has an externally threaded stud  118  formed thereon which engages corresponding internal screw threads formed in the proximate end of the battery/switch housing  20 . A battery  120  is contained in a central cavity formed between the distal end of the battery/switch housing  20  and the proximate end of the coaxial laser housing  22 . Internal screw threads  124  in the battery/switch housing  20  engage corresponding external threads  126  formed in the proximate end of the laser housing  22 . Rotation of the laser housing  22  with respect to the battery/switch housing  20  causes a positive terminal of the battery  120  to activate a switch in the battery/switch housing  20 . 
     The laser housing  22  contains a laser subassembly  122  having a laser source and collimating lens to provide a collimating laser beam which is coaxially aligned along the axis of the gun barrel. Adjustments to the alignment of the laser beam are made with a 3-point adjustment system which includes a pair of windage/elevation adjustment assemblies  127   a,    127   b  and one fixed adjustment screw mechanism  128 . A front cap and lens assembly  130  fixed to the end of the laser housing covers the laser subassembly  122 . 
     FIGS. 8 and 9 illustrate in more detail the battery/switch housing  20  and its contents. The battery/switch housing  20  includes an internally threaded axial bore  132  formed at one end for engagement with the externally threaded stud  118  on the distal end of the coaxial cone  18  shown in FIG. 7. A preferred embodiment has the battery/switch housing  20  and the laser housing  22  made of aluminum. The exterior surfaces of the aluminum battery/switch housing  20  and the laser housing  22  are anodized. All of the threaded surfaces and the interior surfaces are not anodized to facilitate electrical conduction. The distal end of the battery/switch housing  20  includes an innermost cylindrical cavity  134  for containing the components of a switch assembly  136 . The switch assembly  136  includes a compression spring  138  which is contained in the cavity  134  and which has flattened ends. A cup-shaped fiber washer  140  with a counter bore is contained in the cavity  134  and has a center bore  142  formed therethrough for receiving the threads of a contact pin,  144  such as a flat-head brass screw or a smooth pin. The flat-head brass screw  144  has a conical head  146  at one end and an end contact surface  148  at the other end. Solder covers the top surface of the conical head  146  the contact pin is fixed to the fiber washer  14  by being soldered to a nickle-plated washer  149  on the side of the fiber washer  140  opposite the head of the pin  144 . 
     The compression spring  138  is contained within the cavity  134  and pushes against the inside peripheral surface of the fiber washer  140 . The fiber washer  140  is held inside the cavity  134  with a C-ring retainer which is locked into a circumferential groove  148  formed in the wall of the cylindrical cavity  134 . When the compression spring  138  is extended so that the outside edge of the fiber washer  140  contacts the inside surface of the C-ring retainer, the far end  148  of the flat-head screw  144  does not contact the interior end wall  154  of the cavity  134 . 
     The external threads  126  of the laser housing  22  engage the internal threads  124  of the battery/switch housing  20 . Rotation of the screw threads of the laser housing  22  into the screw threads of the battery/switch housing  20  causes the positive terminal  160  of the battery  120  to push against the top  146  of the screw  144  to compress the compression spring  138  such that the end surface  148  of the screw  144  contacts the aluminum surface of the interior end wall  154 . This connects the positive terminal  160  of the battery  120  to the aluminum housing  20 . Rotation of the battery and switch housing  20  in the opposite direction with respect to the laser housing  22  causes the compression spring to extend such that the far end  148  of the flat-head screw  144  or contact pin does not contact the interior end wall  154  of the cavity  134 . This breaks the connection of the positive terminal  160  of the battery  120  to the aluminum housing  20 . 
     FIGS. 10 and 11 illustrate the body of the laser housing  22 . The distal end of the laser housing  22  has a longitudinal central bore  170  formed therein for receiving the cylindrical body of the laser subassembly  122  shown in FIG.  7 . As described herein below, alignment of the laser beam in the laser subassembly  122  is provided using a three-point alignment mechanism which is mounted to the laser housing  22 . The external surface of the distal end of the laser housing  22  has two orthogonal external flat-surfaced dovetailed keyways  172 ,  174  formed thereupon for receiving corresponding dovetailed bases of two windage/elevation adjustment assemblies  176 ,  178 . The windage/elevation adjustment assemblies  176 ,  178  are fixed to the laser housing with bonnet screw threads  180 ,  182 . Each bonnet screw thread  180 ,  182  screw passes through a respective threaded aperture  184 ,  186  in the laser housing  22  such that the ends of respective adjustment screws (not shown) for each windage/elevation adjustment assembly contact the laser subassembly  122  for alignment of the laser beam. One adjustment screw is aligned for movement in a first direction perpendicular to the longitudinal axis of the shaft. A second adjustment screw is aligned for movement in a second direction perpendicular to the longitudinal axis of the shaft and also orthogonal to the first direction of movement of the one adjustment screw. 
     FIG. 11 also illustrates a third element of the three-point alignment mechanism for the optical assembly which is a spring-loaded fixed screw assembly  190 . The spring-loaded fixed screw assembly  190  is screwed into position in a threaded aperture in the laser housing  22  opposite the adjustment screws and at equal obtuse angles with the directions of the adjustment screws to bias the laser subassembly  122  against the ends of the first and the second adjustment screws. 
     FIG. 12 illustrates a typical windage/elevation adjustment assembly, which includes an adjustment screw  192 , a cap  194 , a bonnet  196 , and a fine adjustment retainer ring  198 . Waterproofing of the windage  1  elevation adjustment assembly is accomplished with a first O-ring  200  which engages a circumferential slot  201  formed in the bonnet  196  and a second O-ring  202  which engages another circumferential slot  203  formed in the bonnet  196 . Each one of a pair of springs  204 ,  205  outwardly biases a respective ball of a pair of 1.5 mm. stainless steel balls  206 ,  207 . 
     FIG. 13 shows that the adjustment screw  192  has external threads  210  formed on its midsection with a slot  212  through its upper end. The adjustment screw  192  includes an end contact surface  215  at its bottom end for contact with the laser subassembly  122 . The external threads  210  of the adjustment screw  192  do not extend to the bottom end of the adjustment screw, which provides an unthreaded, smooth side surface  215  at the lower end of the adjustment screw  192 . FIG. 14 shows that the cap  194  has a cupped body  216  with a centrally located depending rectangular tang  218  which engages the slot  212  in the upper end of the adjustment screw. 
     FIGS. 12,  15 A, and  15 B show the bonnet  196  with the external threads  800  which are formed on its lower end and which are then threaded into one of the threaded apertures  184 ,  186  of the laser housing  22  to anchor the windage/elevation adjustment assemblies  176 ,  178  in place. The O-ring  202  in slot  203  provides a water seal between the bonnet and the laser housing. The external threads  210  of the adjustment screw  192  engage internal threads  222  in the bonnet  196  for relative movement of the contact surface  215  at the end of the adjustment screw  192  against the laser subassembly  122 . A horizontal screwdriver slot  221  across the top of the bonnet  196  is used to screw the bonnet  196  to the laser housing  22 . The bonnet has a pair of opposing horizontal radial slots  224 ,  226  formed near its top end for containing one of the springs  204 ,  205 , which outwardly bias the steel balls  205 , 206 . 
     FIGS. 12 and 16 show the fine adjustment retainer ring  198  with a number of pairs of opposing recesses, typically shown as  230 , formed near the top of its inside surface. The fine adjustment retainer ring  198  fits around the bonnet  196 . After assembly of the windage/elevation adjustment assembly, an external cylindrical surface of the retainer ring  198  is press fit inside an inner cylindrical surface of the cupped body  216  of the cap  194 . Each of the springs  204 ,  205  is retained in one of the slots  224 ,  226  and biases one of the pair of steel balls  206 ,  207  into engagement with one of the recesses  230  to provide detented or indexed fine adjustment steps for the adjustment screw  192  as the cap  194  is rotated. A water seal protecting the threads of the screw  192  against moisture is provided with the O-ring  200  which is in the slot  201  of the bonnet and which engages an inside circumferential surface  232  in the retainer ring  198 . 
     FIG. 17 illustrates a base  240  for a windage/elevation adjustment assembly The side edges and the rounded front edge of the base are dovetailed and are received in one of the dovetailed keyways  172 ,  174  formed on the laser housing  22 . A through hole  242  accommodates a windage/elevation adjustment assembly and a recessed ring  244  accommodates the cap  194 . 
     FIG. 18 illustrates the spring-loaded fixed screw assembly  190  which includes a set screw  250  which is screwed into a threaded aperture  260  in the laser housing  22 . A spring  262  is located between the inner end of the screw  250  and a cup-shaped cap, or bushing,  264  which contacts the surface of the laser to bias the laser subassembly  122  against the first and the second adjustment screws  180 ,  182 . 
     FIGS. 19 and 20 illustrate the components of the laser subassembly  122 , which include a hollow pear-shaped laser heatsink  270  which contains a laser diode assembly  272  and an associated circuit board  274  that is soldered to three pins on the laser diode assembly. A disk module  276  is a laminated circuit board with a gold-plated copper layer and apertures which are typically formed therethrough to allow passage of wires  280 ,  281 . The space  284  connects to the negative terminal of the battery. The components of the laser subassembly  272  are fixed in position by encapsulation with a block  282  of an epoxy material. The distal end of the laser heatsink  270  contain a lens  290  attached to an end plug  292 , which is adjusted to collimate a laser beam from the laser diode assembly  272 . 
     A rounded proximate end  294  of the pear-shaped laser heatsink  270  has the largest diameter and is dimensioned to provide a friction fit with a corresponding inner surface of the laser housing  22 . An O-ring  296  is located adjacent to a step  298  at the midsection of the pear-shaped laser heatsink  270 . 
     FIGS. 21 and 22 illustrate a structural arrangement which provides for three-point adjustment of the laser beam from the laser source in the pear-shaped laser heatsink  270 . The inner surface  299  of the laser housing  22  is shaped to provide a close friction fit with the rounded end  294  of the pear-shaped laser housing  294 . This structural arrangement allows precise pivotal movement of the distal end of the laser module  122  as illustrated in FIG. 11 with the three-point alignment produced by the two windage/elevation adjustment assemblies  176 ,  178  and the spring-loaded fixed screw assembly  190 . This allows precise alignment of and orients the laser beam along the axis of the precision bore sight assembly  10  and along the bore of a gun barrel. FIG. 22 shows that the unthreaded, smooth side surfaces  215  at the lower end of the adjustment screws  192  contacts the forward side of the O-ring  296  and compresses the O-ring 10 to 20 per cent to provide friction loading on the ends of the adjustment screws. 
     FIGS. 23 and 24 illustrate an optional lens assembly  300  which includes an end cap  302  and a lens  304  is an exploded, partially sectional view of a front cap and lens. FIG. 22 is a sectional view of an assembled front cap and lens assembly. 
     Another embodiment of a different coaxial laser housing is provided where the windage and elevation settings for a bore sight assembly are initially made with set screws which are then sealed with a locking adhesive. This allows a bore sight assembly to be prealigned at, for example, a factory or a service location. A modified coaxial laser housing is provided which is similar to the housing  22 , but which is smaller in diameter and does not have dovetailed sections for mounting manual adjustment assemblies. Bores for the windage and elevation set screws are provided which correspond to the orthongonally aligned bores  184 ,  186  but which are smaller in size to directly receive the fixed adjustment screws without a bonnet. A plunger biasing assembly, similar to the plunger assembly  190  is also used. The fixed adjustment screws and the plunger assembly are locked in position with a suitable locking material. 
     Note that the bore sight assembly according to the invention is useful for sight alignment of optical scopes, mechanical firearm sights, and laser sighting devices. The bore sight assembly according to the invention is also useful for simulating alignment and firing of a weapon use in a firearms training system. 
     The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.