Abstract:
An apparatus, system, and method for bore sighting a gun. A hollow shell casing is attached to a single light source and then placed in the breech of a gun. Light is projected from the gun onto a pre-calibrated target. The user is then able to adjust the gun sights accordingly. There are a plurality of shell casings interchangeably mountable to the single light source, enabling the user to sight in a variety of guns using only one system. The shell casings may be the same shape as standard shells for the type of gun being sighted in.

Description:
“This application is a continuation of U.S. Ser. No. 09/286,390, filed Apr. 5, 1999 now U.S. Pat. No. 6,061,918.” 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to a gun bore sighting apparatus, and more particularly to a system for using a housing to hold the light source that is used for bore sighting. 
     BACKGROUND 
     It is important to sight in, or adjust, the mechanical or telescopic sight of a gun to be assured that the bullet goes to the exact point that the shooter was aiming at through the sights. Sighting in a gun is usually accomplished by mounting the gun to a fixed stand, aiming at a target, firing a shot, and then adjusting the sight of the gun depending on where the bullet hit the target. The process is repeated until the shooter is satisfied with the accuracy of the sight. 
     Bore sighting using a light source was developed so that a gun could be sighted in without expenditure of ammunition and without the need to go to an area that was safe enough to shoot in. In this method, a light is projected down the barrel of the gun. When the light is emitted, it hits a target placed a predetermined distance away. The center of the light beam is ascertained and the user then adjusts the gun sights accordingly. 
     One problem encountered using bore sighting systems is that the housing holding the light source does not always fit accurately inside the gun chamber to provide an accurate beam of light. Since every different caliber gun has a different size barrel, the user may only get an approximate fitting of housing to chamber, or the user may have to buy a different apparatus for each of their guns. 
     U.S. Pat. No. 5,454,168 to Langner is one bore sighting apparatus which uses a light source. In Langner, the light source is enclosed in a single, cylindrical stepped housing which is placed in the breech of the gun. The housing is stepped so that the single housing is able to fit a limited number of pre-determined different caliber guns. Another bore sighting apparatus is U.S. Pat. No. 4,481,561 to Lanning. In Lanning, the light and light power source are both enclosed inside a housing which is shaped like a standard cartridge. 
     The disadvantages facing a user of a bore sighting apparatus are that either they have to buy a separate unit for each caliber gun they desire to sight in, or they are only able to get an approximate fit to a limited number of different caliber guns. It is desirable to provide a single, inexpensive system for bore sighting in which the housing holding the light source can be accurately positioned in all the different caliber guns a user has. 
     SUMMARY OF THE INVENTION 
     The present invention provides an accurate and inexpensive system for a person who desires to sight in a plurality of different caliber guns. The system includes a single light source having a mounting section, and a plurality of shell casings for different caliber guns that interchangeably mount on the single light source. The shell casings house the light source when it is inserted into the breech of the gun. Since the mounting section of each shell casing is the same standard size, the system allows the user to sight in a wide variety of guns using the single light source and a series of shell casings. 
     In further embodiments, the invention also provides the user with interchangeable muzzle tubes, an external power source for the light source, and a target to be used for sighting in the gun. The interchangeable muzzle tubes also allow the user to use the system to sight in a wide variety of guns. 
     In further embodiments, the invention provides a shell casing that is the same shape as a standard shell for the type of gun being sighted in. This has the advantage of allowing the gun to be bore sighted very accurately because the light source will be centered down the center of the barrel of the gun. Furthermore, because the shell casing itself is in the exact shape of a shell for that caliber of gun, the shell casing will fit snugly and not cause any internal damage to the gun. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view of the bore sighting apparatus in a firearm. 
     FIG. 2A is a detailed view of the light source. 
     FIG. 2B is a detailed view of a shell casing. 
     FIG. 3A is a detailed view of the muzzle tube. 
     FIG. 3B is a detailed view of the muzzle tube handle. 
     FIG. 4 is a view of the target. 
     FIG. 5 is a view of an example of a complete bore sighting system. 
     FIG. 6 is a broader view of a complete bore sighting system. 
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined or that other embodiments may be utilized and that structural changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents. 
     FIG. 1 shows one embodiment of a bore sighting apparatus in a firearm to be sighted in. In FIG. 1, a gun  10 , having a breech  15 , a barrel  14 , a rear sight  17 , a front sight  16 , and a telescopic sight  18 , is mounted to a fixed surface using clamps  11 . A shell casing  20 , attached to a light source unit  28 , is inserted into breech  15  of gun  10 . A muzzle tube  30  is inserted into the end of barrel  14 . Light source unit  28  is connected to a power source  12 , which is located outside of the breech of the gun, by an electrical connector  27 . Power source  12  is activated by a switch  13 . One example of power source  12  is two “AA” batteries, enclosed in a holder  19 . Holder  19  is dimensioned to fit within a shirt pocket. This allows the user to have easy access to it, and allows the power source to be unobtrusive. 
     Light source unit  28  contains a light source  24 , which emits a light which travels through a passage  21  of shell casing  20 , then through barrel  14  of gun  10 . The light is collimated when it goes through muzzle tube  30 , is then emitted from the end of the muzzle tube  30 , and is reflected off of target  40 . 
     FIG. 4 shows an illustrative target  40 . Target  40  has a dark nonreflective section  41 , a reflective section  42 , and a center portion  45 . It also contains a vertical line  43  and a horizontal line  44 . Horizontal line  44  is offset from the center of target  40 . The user adjusts target  40  and gun  10  until the light emitted from gun  10  is centered on center portion  45 . The user then adjusts mechanical sight  17  so that when viewed in conjunction with front sight  16  the sights align with vertical line  43  and horizontal line  44 . Horizontal line  44  is offset a pre-determined distance to allow for the trajectory of the bullet fired from gun  10 . A different horizontal line  44  can be used depending on the distance and trajectory the gun will be fired. Another embodiment is that telescopic sight  18  is used as the sighting mechanism instead of mechanical sights  16 ,  17 . 
     Although having the gun  10  mounted to a fixed surface is one embodiment, the gun  10  can also be sighted in by the user holding the gun  10  and then following the same procedure as set out above. 
     FIG. 2A shows an illustrative light source unit  28 . Light source unit  28  is connected to power source  12  by electrical connector  27 . Electrical connector  27  is a standard electrical cord. The light source  24  is a focused laser, however, those skilled in the art will recognize that an unfocused laser or a standard lightbulb could also be used. Light source unit  28  also has a mounting section  25 . 
     FIG. 2B shows one of the plurality of interchangeable shell casings  20 . Shell casing  20  has a mounting section  23  to allow shell casing  20  to be attached to light source mounting section  25 . In one embodiment, the light source mounting section  25 , and the shell casing mounting section  23  are threaded, however the sections could be connected in any equivalent manner such as friction fitting, press fitting or counterbolt fitting. The shell casing  20  also contains a passage  21  axially located which goes through the shell casing. Passage  21  allows the light from light source  24  to pass through shell casing  20 . Shell casing passage  21  terminates at a center tip  22  of shell casing  20 . 
     Shell casing  20  is substantially similar in shape and length to a standard cartridge for a gun of the caliber being sighted in. This is so that the shell casing will fit with close tolerance in the chamber, and also so that it will not cause any damage to the inside of the gun. By being the same length as a standard shell, the shell casing also will have a high degree of stability inside the chamber of the gun  10 . The advantage is that the shell casing will be supported for its full length, and will not have any wobble. 
     One material for shell casing  20  is brass. This adds the advantage of being malleable and easy to machine, yet hard and relatively inexpensive. Brass is a common choice of shell manufacturers for the same reasons as noted above. However, those skilled in the art will recognize that other materials can be chosen based on need and economics. 
     FIGS. 3A and 3B show a view of an interchangeable muzzle tube system. One of a plurality of interchangeable muzzle tubes  30  has a mounting section  33  and central passage  34 . A single muzzle tube handle  36  has a mounting section  35  that fits all muzzle tubes. Muzzle tube mounting section  33  is inserted into handle mounting section  35  and the user inserts muzzle tube  30  into the muzzle of gun  10 . The single muzzle tube handle  36  allows muzzle tube  30  to be easily removed. The mounting sections  33 ,  35  are shown as threaded sections, however the sections could be connected in any equivalent manner such as friction fitting, press fitting or counterbolt fitting. Another embodiment of a muzzle tube system includes a plurality of compressible O-rings  31 . Each o-ring having a different external diameter, to allow muzzle tube  30  to fit tightly into the muzzle of different caliber gun barrels. 
     FIGS. 5 and 6 show an example of a complete system according to the invention. The user buys the system containing the necessary parts to practice the invention as described above. The bore sighting system optionally includes a carrying case  61 , a single power source  12 , single light source unit  28 , a plurality of shell casings  20 ,  50 - 1 ,  50 - 2 ,  50 - 3 ,  50 - 4 , a plurality of muzzle tubes  30 ,  51 - 1 ,  51 - 2 ,  51 - 3 ,  51 - 4 , a single muzzle tube handle  36 , and target  40 . The user only need to buy this one system to be able to practice the invention on multiple types of guns. A bore sighting system could also contain any permutation of the parts described above. An advantage of the system is that it is inexpensively expandable. The user can originally buy a single light source unit and a single muzzle tube handle, and then separately purchase the interchangeable shell casings and interchangeable muzzle tubes for their guns as needed. 
     As shown in FIG. 5, each shell casing  20 ,  50 - 1 ,  50 - 2 ,  50 - 3 ,  50 - 4  has a different size and shape to match the caliber of gun  10 . However, the mounting section  23 ,  53 - 1 ,  53 - 2 ,  53 - 3 ,  53 - 4  of each shell casing  20 ,  50 - 1 ,  50 - 2 ,  50 - 3 ,  50 - 4  is the same as every other mounting section  23 ,  53 - 1 ,  53 - 2 ,  53 - 3 ,  53 - 4 , and also equal in size to the mounting section  25  of the single light source unit  28 . This allows the shell casings  20 ,  50 - 1 ,  50 - 2 ,  50 - 3 ,  50 - 4  to be interchangeably mounted on the light source unit  28  depending on the caliber size of the gun  10  that is being sighted in. Each shell casing  20 ,  50 - 1 ,  50 - 2 ,  50 - 3 ,  50 - 4  has a passage  21 ,  52 - 1 ,  52 - 2 ,  52 - 3 ,  52 - 4 , respectively. Examples of shell casing sizes include casings for 0.22, 30—30, 30-06, 7mm, 270, and 300 caliber guns. 
     Also shown in FIG. 5 is one embodiment of the invention in which there are five muzzle tubes  30 ,  51 - 1 ,  51 - 2 ,  51 - 3 ,  51 - 4 , each having a different outside diameter. However, the mounting sections  33 ,  54 - 1 ,  54 - 2 ,  54 - 3 ,  54 - 4  of each of the muzzle tubes  30 ,  51 - 1 ,  51 - 2 ,  51 - 3 ,  51 - 4  are the same size as each other and the same size as the mounting section  35  of the single muzzle tube handle  36 . This allows muzzle tubes  30 ,  51 - 1 ,  51 - 2 ,  51 - 3 ,  51 - 4  to be interchangeably mounted on the single muzzle tube handle  36  depending on the caliber of the gun  10  that is being sighted in. Each muzzle tube  30 ,  51 - 1 ,  51 - 2 ,  51 - 3 ,  51 - 4  has a central passage  34 ,  55 - 1 ,  55 - 2 ,  55 - 3 ,  55 - 4 , respectively. 
     It is to be understood that the above description is intended to be descriptive and not restrictive. Other embodiments of the invention will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.