BACKGROUND OF THE INVENTION 
   Many firearms have adjustable sights so that the sights can be adjusted to enable the firearm to hit what the shooter is aiming at. This is particularly true of rifles and the like that are expected to be fired at longer distances in situations where the impact of the fired bullets may shift due to such factors as gravity and wind that act upon the fired bullets. Many firearms have a fixed front sight with a variable rear sight that is adjustable for elevation and possibly also for windage. However, there are few firearms that have front sights that are adjustable for elevation. 
   The well known AR-15 or M-16 type or family of firearms is an example of a family or type that has an elevation adjustable front sight. The M-16 type front sight has an externally threaded lower conical portion that screws into a threaded hole in a sight base and the sighting elements is located on the outer end of the threaded portion. A circumferential flange with outer indentations is located around the base of the sight element and these indentations permit the threaded shaft to be rotated by the user by inserting the point of a bullet or the like into an indentation and then applying a lateral or rotatable force to cause the threaded shaft portion to be threaded into or out of the threaded hole in the sight base. When the threaded portion is threaded into the threaded hole, the front sight is lowered and the firearm will normally shoot higher. Conversely, when the threaded portion is screwed out of the threaded hole, the front sight is extended or elevated and the firearm will normally shoot lower. 
   It has been determined that it is beneficial to provide the shooter with two or more different front sight elements such as blades or posts. This gives the shooter a choice of front sight elements to suit his or her particular need or preference. For instance, a small blade type front sight might be desired for precision or target shooting but a larger size blade type sight might be desired for hunting game where speed is required and a larger sight is beneficial. Unfortunately, mounting such a dual convertible front sight on a rotating elevation adjustable front sight, so that it can be switched by the user, presents severe problems because, if the front sight is rotated to present a different front sight blade or the like, the rotation of the sight also moves the front sight up or down and this changes the point of impact of the bullet which is not acceptable. 
   This invention permits a rotatable elevation adjustable front sight to be used with a plurality of front sight elements such as blades, dots or the like without changing the elevation of the sight. Consequently, with this invention the shooter can readily change the front sight element to suit the particular shooting requirements without changing the point of impact of the bullets when the firearm is fired. In one embodiment of the invention a wide range of front sight elements can be readily substituted by the shooter. The front sight invention is capable of replacing the front sight in the M-16 type or family of firearms. 
   SUMMARY OF THE INVENTION 
   This invention relates to adjustable front sights and more particularly to an elevational adjustable front sight that has a threaded portion that screws into and out of a threaded hole in a front sight base to provide elevational adjustments. 
   It is therefore an object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements. 
   It is an object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm. 
   It is an object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm that is also adjustable by the user of the firearm for elevation. 
   It is an object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm that also adjustable by the user of the firearm for elevation where the user can select the the desired front sight element without changing the elevation setting. 
   It is an object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm that can replace the existing M-16 type firearm front sight. 
   It is object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm that is adapted to be rotatably secured in the existing threaded aperture for the existing M-16 type firearm front sight. 
   It is an object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm that is adapted to be rotatably secured in the existing threaded aperture for the existing M-16 type firearm front sight that is easy for the firearm user to install. 
   It is an object of the invention to provide an adjustable firearm front sight kit with a front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm that is adapted to be rotatably secured in the existing threaded aperture for the existing M-16 type firearm front sight that is easy for the firearm user to install that includes tools to assist the firearm user in installing and using the front sight. 
   It is an object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm that is also adjustable by the user of the firearm for elevation where the user can select the the desired front sight element without changing the elevation setting that has a plurality of removable front sight elements. 
   It is an object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm that is also adjustable by the user of the firearm for elevation where the user can select the the desired front sight element without changing the elevation setting that is simple in its operation. 
   It is an object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm that is also adjustable by the user of the firearm for elevation where the user can select the the desired front sight element without changing the elevation setting that is maintenance free. 
   It is an object of the invention to provide an adjustable firearm front sight that has the capability of providing a plurality of front sight elements that can be chosen by the user of the firearm that is also adjustable by the user of the firearm for elevation where the user can select the the desired front sight element without changing the elevation setting that does not wear out. 
   These and other objects of the invention will be apparent from the following description of the adjustable front sight invention that includes a lower rotatable front sight insert member adapted to be secured to a front sight base on the forward portion of a firearm barrel and an upper front sight insert member rotatably secured to the upper portion of the lower rotatable front sight insert member with the upper front sight insert member having a plurality of front sight elements that are selectable by the firearm user by rotating a portion of the upper front sight insert member that is rotatably secured to the upper portion of the lower rotatable front sight insert member. This front sight has element selecting and positioning means for permitting the user to select and position the front sight element for use by rotating a portion of the upper front sight insert member without changing the elevation setting of the front sight. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be hereinafter described with reference to the accompanying drawings in which: 
       FIG. 1  is a side elevational view of the front sight area of a prior art M-16 type firearm with portions thereof broken away; 
       FIG. 2  is a side elevational view of the front sight area of an M-16 type firearm with the adjustable front sight invention with portions thereof broken away; 
       FIG. 3  is a side elevational view of the lower portion of the adjustable front sight invention set forth in  FIG. 2   
       FIG. 4  is a top plan view of the lower portion of the adjustable front sight invention set forth in  FIG. 2 ; 
       FIG. 5  is a front elevational view of the upper portion of the adjustable front sight invention set forth in  FIG. 2 ; 
       FIG. 6  is a bottom plan view of the upper portion of the adjustable front sight invention set forth in  FIG. 2 ; 
       FIG. 7  is a is a side elevational view of the front sight area of an M-16 type firearm with an additional embodiment of the adjustable front sight invention with portions thereof broken away; 
       FIG. 8  is a front elevational view of the upper portion of the adjustable front sight invention set forth in  FIG. 7 ; 
       FIG. 9  is a side elevational view of the portion of the upper portion of the adjustable front sight invention set forth in  FIG. 8 ; 
       FIG. 10  is a bottom plan view of the portion of the upper portion of the adjustable front sight invention set forth in  FIG. 9 ; and 
       FIG. 11  is a side elevational view of a tool kit for use with the upper portion of the adjustable front sight invention set forth in FIGS.  2  through  9 . 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring first to  FIG. 1 , a side elevational view of a prior art M-16 type elevation adjustable front sight with portions broken away and in section is illustrated and is designated generally by the number  10 . The M-16 type sight  10  comprises a front side body  12  with conventional front sight protectors  14  located on its upper end portion  16 . For clarity only one front sight protector  14  is illustrated. A generally flat surface  18  is located between the sight protectors  14  and a shallow depression  20  is located in this surface  18 . A conventional threaded hole  22  extends downward into the front sight body  12  from the depression  20  and this threaded hole  22  is sized and shaped to accept a conventional prior art front sight insert  24  with its threaded portion  25 . The sight insert  24  has a conventional front sight post  26  on its upper end portion  28 . An unthreaded hole  30  is located in front of the threaded hole  22  and extends downward from the depression  20  into the front sight body  12  parallel to the threaded hole  22 . This unthreaded hole  30  contains a conventional generally cylindrical detent  32  and a detent coil spring  34  that is located in the hole  30  below the detent  32  with a portion  36  that extends into a hollow cylindrical open bottom portion  38  in the detent  32 . The upper surface  40  of the detent  32  has a short cylindrical projection  42  that is sized and shaped to fit into a semicircular cut out portion or indentation  44  in the circular flange portion  46  of the upper end portion  28  of the front sight insert  24 . 
   In order to use the prior art front sight  10  to adjust it for the changes in elevation, the user pushes downward on the cylindrical projection  42  with the point of a bullet or the like so that the projection  42  is pushed below the flange portion  46 . With the same bullet point (not shown) side pressure can be exerted on the edge of the cut out portion  44  to cause the sight insert  24  to rotate clockwise or counterclockwise. This rotational movement causes the front sight post  26  to move upward or downward due to the threaded portion  25  and the threaded hole  22 . Consequently, the prior art front sight  10  is adjustable for elevation. 
   The elevation adjustable firearm front sight with user changeable sighting element of this invention is set forth in  FIG. 2  as well as  FIGS. 3 ,  4 ,  5  and  6  and is designated generally by the number  48 . As indicated in  FIG. 2 , the adjustable front sight invention  48  uses the existing prior art M-16 front sight body  12  with the shallow depression  20 , the threaded hole  22 , and unthreaded hole  30 . The front sight invention  48  also uses the existing detent coil spring  34 , but uses a different detent  35  that has a longer cylindrical projection  37  that has a length L. 
   The adjustable sight invention  48  uses basically a two piece front sight insert  50  in place of the prior art single piece front sight insert  24 . The two piece front sight insert  50  has a lower front sight insert member  52  and an upper front sight insert member  54 . The lower front sight insert member  52  has a lower threaded portion  56  that is sized and shaped to be threaded into the threaded hole  22  in the front sight body. As illustrated in  FIGS. 2 ,  3  and  4 , a thin circular shaped flange portion  58  is located immediately above the threaded portion  56 . This circular shaped flange portion  58  has a series of semicircular cut out portions  60  located in the outer circumferential portion  62  of the flange portion  58 . A raised circular shaped bearing portion  63  extends upward from the upper surface  64  of the flange portion  58  and this bearing portion  63  has an outer circular shaped bearing surface  66 . A connecting projection  68  extends upward from the bearing surface  66 . A portion of this connecting projection  68  has a circumferential semicircular groove  70  in its outer surface that is sized and shaped to accept a portion of a roll pin  72 . 
   As illustrated in  FIG. 2 , the upper front sight insert member  54  is located immediately above the lower front sight insert member  52 . As illustrated in  FIGS. 2 ,  5  and  6 , the upper front sight insert member  54  has a thin enlarged circular shaped lower flange portion  74  whose central portion rests upon the bearing portion  63  of the lower front sight insert member  52 . The lower flange portion  74  has four identical semicircular cut out indentations  76  in its outer circumferential surface. An enlarged generally rectangular support portion  78  is located immediately above the flange portion  74 . A hole  80  is centrally located in the flange portion  74  and extends into the support portion  78  and this hole  80  is sized and shaped to receive the connecting projection  68  that is located on the upper portion of the lower front sight insert member  52 . The support portion  78  has a hole  82  extending through it that is sized and shaped to receive the roll pin  72 . 
   The hole  82  is located in the support portion  78  so that a portion of the roll pin  72  fits into the semicircular groove  70  in the connecting projection  68 . In this manner the upper front sight insert member  54  is rotatably connected to the lower front sight insert member  52 . It is important to note that the roll pin  72  is installed with its slot portion  86  located outward or away from the semicircular groove  70  in the connecting projection  68 . 
   A thin generally rectangular shaped front sight blade portion  88  extends upward from the support portion  78 . The upper end portion  90  of the front sight blade portion  88  has a semicircular cut out portion  92  and two circular holes  94  and  96  that are on the same axis extend through the upper end portion  90  of the front sight blade portion  88 . The hole  96  has an enlarged outer counter bored section  98 . A fiber optic front sight insert member  100  is sized and shaped to fit into the respective holes  94  and  96  as well as the counter bored section  98 . When installed, the fiber optic rod insert member  100 , of a color of the user&#39;s selection, is melted by heat at both ends. At the counter bored hole  98  the rod insert member  100  melts into the counter bored section  98 , retaining the fiber optic rod insert member  100  and providing a small visual sighting reference dot  188 . The circular hole  94  at the other end of the blade portion  88  is configured so that the fiber optic rod insert member  100  melts outside the hole  94  when heated to provide a larger slighting reference dot  192  for the user. By rotating the blade portion  88 , the user can select the small or large sight reference dot  188  or  192 . Although a heat melted fiber optic rod insert member  100  is described in connection with the preferred embodiment of the invention  48 , it will be understood by those skilled in the art that other types of insert members and the like my be used in place of the fiber optic rod insert member  100  that has heat melted ends. 
   As indicated in  FIG. 2 , an alternative upper front sight insert member designated generally by the number  102  is also provided. This upper front sight insert member  102  is substantially the same as the previously described upper front sight insert member  54  except that the dimensions for the circular holes  104  and  106 , and the counter bore section  108  for the fiber optic front sight insert member  110  are greater than those for the same holes  94  and  96 , the counter bore  98  and the fiber optic insert front sight insert member  100  of the upper front sight insert member  54 . This extra alternative upper front sight insert member  102  allows the user of the front sight  48  to select a different fiber optic front sight insert member that has dimensions or color that are suitable for his or her shooting needs. To install the upper front sight insert member  102 , the roll pin  72  is removed from the hole  82  in a conventional manner. Then, the upper front sight insert member  54  is removed and the upper front sight insert member  102  is installed in its place on the lower front sight insert member  52  and the roll pin  72  is inserted into the hole  82 . 
     FIGS. 7 ,  8 ,  9  and  10  illustrate an alternative embodiment for the upper front sight insert member  54  and this alternative is designated generally by the number  112  and is adapted to be used with the previously described the lower front sight insert member  52 . As illustrated in  FIGS. 7 through 10 , the alternative embodiment  112  comprises an upper front sight base member  114  and a removable front sight blade member  116 . The upper front side base member  114  has a thin enlarged circular shaped lower flange portion  118  whose central portion rests upon the bearing portion  63  of the lower front sight insert member  52 . The lower flange portion  118  is identical to the previously described flange portion  74  and it has four identical semicircular cut out portions or indentations  120  in its outer circumferential surface that are identical to the cut out portions or indentations  76  of the previously described flange portion  74 . An enlarged generally rectangular support portion  122  is located immediately above the flange portion  118  and a hole  124  is centrally located in the flange portion  118  and extends into the support portion  122 . This hole  124  is sized and shaped to receive the connecting projection  68  that is located on the upper portion of the lower front sight insert member  52 . The support portion  122  has a hole  128  extending through it that is sized and shaped to receive the previously described roll pin  72  that is installed in the previously indicated manner. 
   The support portion  122  has truncated upside down shaped projection  130  extending upward from its upper surface  132 . this projection  130  fits into a groove  134  that is located in the lower surface  136  of the front sight blade member  116 . This groove  134  is sized and shaped to tightly receive the projection  130 . The rest of the removable front sight blade member  116  is similar to the previously described front sight blade portion  88 . A semicircular cut out portion  138  is located in the upper end portion  140  of the front sight blade member  116 . Two circular holes  142  and  144  that are on the same axis extend through the upper end portion  140  of the front sight blade member  116  and the hole  144  has an enlarged outer counter bored section  146 . A fiber optic front sight insert member  148  is sized and shaped to fit into the respective holes  142  and  144  as well as the counter bored section  146 . This fiber optic front sight insert member  148  is melted at its ends by heat in the previously described manner with reference to the fiber optic insert member  100 . A threaded hole  150  extends downward through the front sight blade member  116  to the upper portion of the groove  134 . A threaded set screw  152  is threaded into the threaded hole  150  and its lower end portion is tightened, using a conventional screw driver, against the upper surface  156  of the projection  130  to lock or secure the projection  130  in place within the groove  134  so that the front sight blade member  116  is secured to the front sight base member  114 . It should be noted that a circular cross section hole  157  extends through the fiber optic front sight insert member  148  adjacent the threaded hole  150  to permit access to threaded hole  150 . This hole  157  is of sufficient size to accept that shaft and tip of a conventional small screw driver. 
   As indicated in  FIG. 7 , one or more alternative front sight blade members may be provided, only one of which is illustrated and is designated generally by the number  158 . This alternative front sight blade member  158  is substantially identical to the previously described front sight blade member  116  except that the dimensions for the circular holes  160  and  162 , and the counter bore  164  for the fiber optic front sight insert member  166  are different than those for the same holes  142  and  144 , the counter bore  146  and the fiber optic insert front sight insert member  148  of the front sight blade member  116 . The extra alternative front sight blade members such as the front sight blade member  158  allow the user of the front sight  48  the ability to readily select a different fiber optic front sight insert member that has dimensions or color that are suitable for his or her shooting needs. 
   In the preferred embodiment, the elevation adjustable firearm front sight with the user changeable sighting element  48  or the alternative embodiment with the upper front sight insert member  112  is supplied with a tool kit that is set forth in FIG.  11  and is designated by the number  168 . The tool kit  168  comprises a detent tool  170  and a front sight tool  172 . The detent tool  170  comprises an L-shaped member with a long straight handle portion  174  and an adjacent shorter straight tool portion  176  that has its along axis at 90 degrees to the long axis of the long straight handle portion  174 . The front sight tool  172  has a circular cross section handle portion  178  and an adjacent smaller diameter circular cross section tool portion  180  whose outer end portion  182  has a stepped shaped indentation  184  that is shaped and sized to receive the front sight blade portion  88  and a portion of the support portion  78  of the front sight  48  or the equivalent structure of the other embodiment. 
   The elevation adjustable firearm front sight with a user changeable sighting element invention  48  illustrated in  FIGS. 2 through 6  is made in a conventional manner using conventional machining techniques and conventional materials and finishes known in the art. The same is true for the alternative embodiment for the upper front sight insert member  54  that is designated generally by the number  112  and is illustrated in  FIGS. 7 through 10 . 
   The front sight invention  48  is used in the following manner. First, the conventional front sight insert  24  is removed from the threaded hole  22  in the front sight body  12 . This is a accomplished by depressing the cylindrical projection  42  of the detent  32  using the point of a bullet or some other suitable object or the short end  176  of the detent tool  170 . While the detent projection  42  is depressed, the front sight insert  24  is rotated in a conventional manner in a counter clockwise direction until the front sight insert  24  is free from the threaded hole  22  in the front sight body  12 . 
   After the front sight insert  24  is removed from the hole  22 , the prior art detent  32  is also removed and it is replaced by the new detent  35  that has the longer cylindrical projection  37 . Then the two piece front sight insert  50  is mounted in the prior art threaded hole  22  in the front sight body  12 . In doing this, the lower front sight insert  52  with its lower threaded portion  56  is threaded into the threaded hole  22 . To do this the new detent  35  will be depressed by using the tool portion  176  of the detent tool  170  to depress the detent  35 . The lower front sight insert member  52  is rotated through the use of its circular shaped flange portion and its cut out portions  60  to achieve the desired elevation for the two piece insert  50 . 
   Once the proper elevation has been set, the user can then select the end of the fiber optic insert member  100  that the user wants to view when using the front sight  48 . In this connection, it should be noted that the circular hole  96  for the fiber optic insert member  100  has an enlarged counter bored section  98  with the smaller melted visual sight reference whereas the circular hole  94  in the opposite end of the front sight blade portion  88  does not have the confining counter bore and the adjacent heat melted sight reference is larger. 
   Consequently, in view of the previous discussion related to the heat melting of the ends of the fiber optic rod insert member  100 , the user that is viewing the end  186  of the blade portion will see a large fiber optic dot  192  and the user that is viewing the opposite end  190  of the blade portion  88  will see a much smaller fiber optic dot  188  that is confined by the outer counter bored section  98  for the front sight fiber optic insert member  100 . To select the proper fiber optic dot  188  or  192 , the user depresses the projection  37  of the detent  35  using the tool portion  176  of the detent tool  170  to depress the projection  37  of the detent  35  just sufficiently so that the detent projection  37  clears the lower flange portion  74 , but not the flange portion  58  of the lower front sight insert member  52 . This allows the elevation setting to remain fixed since the projection  37  of the detent  35  is still in one of the cut out portions  60  in the flange portion  58  and hence the lower front sight insert member  50  cannot rotate and change the elevation setting of the front sight  48 . The user then rotates the front sight blade portion  88  so that the desired fiber optic dot  188  or  192  is facing to the rear and can be used for sighting purposes. This rotation of the front sight blade portion  88  is best accomplished by the user using the front sight tool  172  and by placing the stepped shaped indentation  184  over the upper end portion  90  of the front sight blade portion  88  and twisting the front sight tool  172 . 
   The other front sight blade portions are rotated into the desired positions in the same manner as the front sight blade portion  88 . Also, the rotation for the upper front sight insert member  112  is accomplished in an identical manner. However, if it is desired that the front sight blade member  116  be changed, then the set screw  152  is loosened and the projection  130  is moved laterally out of the groove  134  of the front sight blade member  116 . Then, an alternative front sight blade member  158  is placed onto the projection  130  and the set screw  152  is inserted and used to secure the front sight blade member  158  in place on the front sight base member  114  in the same manner as the the front sight blade member  116 . 
   Although the invention has been described in considerable detail with reference to certain preferred embodiments, it will be understood that variations or modifications may be made within the spirit and scope of the invention as defined in the appended claims.
An elevation adjustable firearm front sight with user changeable sighting elements that includes a lower rotatable front sight insert member adapted to be secured to a firearm front sight base and an upper front sight insert member rotatably secured to the upper portion of the lower rotatable front sight insert member. The front sight insert member has a plurality of front sight elements that are selectable by the firearm user by rotating the upper front sight insert member that is rotatably secured to the upper portion of the lower rotatable front sight insert member. This sight has provisions for permitting the user to select the front sight element by rotating the front sight mounting member without changing the elevation setting of the front sight.