# Patent

## Title
Firearm with interchangeable calibers and/or improved sights

## Abstract

A replacement slide assembly for a pistol, the slide assembly having a barrel assembly with a barrel and a firing chamber. The barrel assembly also has a guide member which is a protrusion that extends horizontally outward from the barrel assembly. The replacement slide assembly also includes a housing with an interior wall that defines a groove that receives the guide member. The guide member and the groove in the housing are located forward of a firing pin assembly also mounted within the housing. The slide assembly or any firearm also includes an adjustable sight assembly that permits interchangeability between different types of sights without requiring that the firearm be re-sighted.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application No. 61/627,035 entitled CONVERSION SLIDE WITH RETRO-FITTED SIGHTS filed Sep. 16, 2011 under 35 U.S.C. §119 and is hereby incorporated by reference in its entirety.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to firearms and, in particular, concerns a system and method of converting the caliber of an automatic pistol from a first caliber to a second and also an improved sight system.
2. Description of the Related Art
Automatic pistols are very well known. Many of these pistols comprise a frame that houses a trigger assembly and a magazine. A spring biased, movable slide assembly is then mounted on top of the frame. The slide includes a housing, a firing chamber, a firing pin assembly and a barrel. In operation, the user pulls the trigger which induces the firing pin assembly to strike a cartridge in the chamber, causing the cartridge to fire, resulting in the slug or projectile(s) travelling down the barrel. With slide based pistols, the detonation of the cartridge also results in the slide housing recoiling backwards over the frame and barrel and to then slide forward back into the shooting position as a result of the spring biasing of the slide housing. This backwards and forwards motion of the slide housing performs several functions, including ejecting the spent cartridge casing, cocking the firing pin assembly and loading another cartridge into the chamber when the slide housing comes forward.
Typically, slide assemblies are specific to a particular pistol and allow the shooter to only shoot the caliber of bullet that the barrel, magazine and firing chamber are sized to receive. However, it is often desirable for shooters to be able to practice shooting with less powerful and/or less expensive ammunition. While slide assemblies on many pistols are removable, the easy interchangeability of the slide assemblies is limited.
More specifically, some pistols, such as those manufactured by Glock Ges.m.b.H. of Austria are designed to be modular such that the various components, e.g., the slide assembly, the magazine, the trigger assembly, etc., can be easily removed from the frame of the pistol. However, while removing a slide and a magazine is relatively easy with GlockTM pistols, changing the slide and magazine to a different caliber is more complicated.
For example, it is often desirable to be able to fire low power and inexpensive .22 caliber ammunition in more powerful, higher caliber pistols. The lower power .22 caliber ammunition allows a shooter to become familiar with the feel of the pistol while shooting a round that has less recoil and is considerably cheaper than larger pistol calibers. Moreover, the reduced power of the smaller .22 caliber ammunition allows it to be shot at smaller range facilities and the like.
However, switching to a smaller round like a .22 caliber is complicated by the fact that the smaller caliber may not have sufficient power to cycle the slide housing back and forth over the frame. Moreover, many slide pistols, such as GlockTM pistols are designed such that the barrels pivot with respect to the slide housing so as to facilitate loading of the next round in the magazine. Often smaller caliber cartridges, such as the .22 caliber, produce insufficient recoil of the slide assembly to both cycle the slide housing over the frame and pivot the barrel with respect to the slide housing to load the next cartridge in the magazine into the firing chamber.
Some efforts have been made by others to address this issue by designing the magazine to spring load the next cartridge in line with the firing chamber such that the firing chamber and barrel do not pivot with respect to the slide. In these products, the barrel and firing chamber slide straight back and the spring loaded magazine urges the next cartridge into the firing chamber when the firing chamber is exposed to the magazine. This requires that the barrel and firing pin assembly move in a straight line with respect to the slide and frame.
To achieve the straight line motion of the barrel assembly with respect to the slide housing, the prior art product incorporates a guide that is engaged with the housing of the trigger assembly. The guide member and the trigger assembly are interconnected in such a way that the barrel and firing pin assembly cannot be removed from slide housing without the removal of the firing pin assembly. Alternatively, in some prior art products, the guide member has to be interconnected to the barrel assembly which complicates the installation and removal process.
This complicates the process of disassembling the converted barrel which further complicates cleaning of the components of the replacement slide assembly and the complexity of interaction between the components of the conversion slide makes the conversion slide potentially less reliable and more expensive Thus, there is a need for an improved conversion slide assembly for slide based semi-automatic pistols.
A further difficulty with both original and replacement slide assemblies and firearms in general is that the assemblies do not accommodate aftermarket sight assemblies in a convenient fashion. Most slide assemblies include fixed iron sights at the front and rear of the slide housing. It is often desired to replace the iron sights with other aftermarket sights. Often, the original rear sight is simply positioned within a groove extending across the width of the housing. By moving the original rear sight from left to right, the shooter can adjust the point of aim of the rear sight.
Similarly, when the user wishes to replace the rear sight with an aftermarket sight, the aftermarket sight is positioned within the same groove and must be adjusted back and forth to the correct position. Thus, any change between sights requires that the pistol be re-sighted by the shooter. Alternatively, the shooter can place the replacement sight on the housing above the original sight but this results in the aftermarket sight not replicating the sight picture of the original sight which can affect shooting performance. Hence, there is also a need for a slide assembly, and firearms in general, that facilitates easier interchangeability between sights.
SUMMARY OF THE INVENTION
The aforementioned needs are satisfied by the present invention which, in one implementation, comprises a replacement slide assembly for a pistol having a frame and a trigger assembly of a first caliber comprising a barrel assembly with a firing chamber and a barrel defining an axis wherein the barrel assembly defines a first protruding member. In this implementation, the slide assembly also comprises a slide housing that is adapted to be positioned on the frame of the pistol such that the recoil of the pistol induces the slide housing to slide backwards along the frame, wherein the slide housing defines a groove having a first section that extends in a direction parallel to the axis of the barrel that receives the first protruding member so that the engagement between the first protruding member and the first section of the groove induces the slide housing to slide in a direction parallel to the axis of the barrel of the barrel assembly.
In another implementation, the aforementioned needs are satisfied by a firearm comprising: a barrel assembly having a firing chamber and a barrel wherein the barrel defines an axis and a frame that includes a trigger assembly, wherein the barrel assembly is mounted in a defined relationship to the frame. In this implementation the firearm also comprises a surface that is mounted in a defined relationship to the barrel, wherein the surface defines a first recess with at least one mounting component and a sight platform that is sized to be positioned within the recess and engage with the mounting component such that the sight platform is maintained in a fixed relationship with the barrel axis when mounted within the recess and engaged with the mounting component and wherein the sight platform defines an adjustable sight mounting location. In this implementation the firearm also comprises a sight that is mounted in the adjustable sight mounting location so that the sight can be adjusted into a first orientation with respect to the sight platform so as to be in a defined relationship with the axis of the barrel and wherein the sight platform can be removed from the recess and returned to the recess and the sight is maintained in the same first orientation with respect to the axis of the barrel.
These and other objects and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a pistol incorporating one embodiment of a replacement slide assembly;
FIG. 2A is an exploded perspective view of the replacement slide assembly of FIG. 1;
FIG. 2B is a perspective view of the replacement slide assembly of FIG. 1 illustrating the interior portions of the slide assembly;
FIG. 2C is a side view of the replacement slide assembly of FIG. 1 showing the interior components in phantom;
FIG. 2D is a side view of the replacement slide assembly of FIG. 1 as it is positioned on the frame of the pistol of FIG. 1;
FIG. 3 is a cross-sectional view of one firing pin assembly of the replacement slide assembly of FIG. 1;
FIG. 4 is a perspective view of slide housing for a pistol with a platform for an interchangeable sight assembly;
FIG. 5 is a perspective view of a mounting block for interchangeable sights; and
FIGS. 6A and 6B are side views of the sight assemblies of FIGS. 4 and 5.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference will now be made to the Figures wherein like numerals refer to like parts throughout. Referring to FIG. 1, an exemplary semi-automatic pistol 100 is shown. This pistol 100 can comprise any of a number of different pistols without departing form the scope of the present invention and can, in one or more embodiments, comprise a Model 17, 19 or 26 GlockTM pistol of varying calibers. As discussed below, the original slide of the pistol 100 has been replaced with a replacement slide 102 that houses a different caliber of firing chamber and barrel to allow the pistol 100 to be used with a different caliber of cartridge.
In one specific embodiment discussed herein, a standard 9 mm or .40 caliber slide assembly has been replaced by a .22 caliber slide assembly to allow the shooter to shoot the pistol with reduced power and lower cost ammunition. However, it will be apparent that the replacement slides 102 discussed below can comprise any of a number of different calibers of slides without departing from the scope of the present invention.
As shown in FIG. 1, the pistol 100 includes the slide assembly 102 that is mounted on a frame 104. The frame 104 defines a hand grip 106 and also has a trigger assembly 110 that the shooter uses to fire the pistol 100 in a well known manner. As will be discussed below, the interior of the handgrip includes a magazine, such as a detachable box magazine 180 (FIG. 2D), that holds cartridges to be fired by the pistol.
The slide assembly 102 includes a barrel 132 and a firing chamber 130. Cartridges are inserted into the firing chamber and a firing pin assembly (discussed below) is actuated by the trigger assembly to fire the cartridges in the firing chamber 130 propelling a slug or other projectile(s) down the barrel 132 in a well-known manner. The firing of the cartridge results in recoil that causes a housing 136 of the slide assembly 102 to move backwards toward the rear of the frame 104 in a manner that will be described in greater detail below. This results in the re-cocking of the firing pin assembly and also results in a cartridge in the magazine being loaded into the firing chamber 130 and the empty shell of the fired cartridge being ejected from the firing chamber 130 in a well-known manner.
As is also shown in FIG. 1, the replacement slide assembly 102 also includes sights that comprise a sight mount 120 and a front sight 122. The sights of the slide assembly can comprise either fixed or adjustable iron sights or can comprise optical sights. As will be discussed in greater detail below, the pistol 100 can also include an interchangeable sight assembly 200 (FIGS. 4-6) that permits interchanging of the sights without re-sighting of the pistol to accommodate the different sights.
Referring now to FIGS. 2A-2D, the replacement slide assembly 102 will be described in greater detail. The replacement slide assembly 102 includes a barrel assembly 126 that includes a firing chamber 130 that receives the cartridge from the magazine in a well-known manner and a barrel 132. The barrel assembly 126 is positioned within a space 134 (FIG. 2B) in the slide housing 136 of the slide assembly 102 so that the barrel is positioned adjacent or protrudes slightly outward of a barrel opening 140 of the slide housing 136.
The space 134 of the slide housing 136, in this embodiment, extends the full length of the slide housing so as to be partially enclosed by two side walls 142a, 142b. The forward portion 144a of the space 134 receives the barrel assembly 126 and the rear portion 144b of the space receives a firing pin assembly 146. There is an ejection part 150 that defines a border between the forward portion 144a and the rear portion 144b of the interior space 134 of the housing 136.
As is also shown in FIGS. 2A-2C, the inner wall of the side wall 142a includes a groove 154 that receives a boss or protrusion 152 that is formed on a side wall of the firing chamber 130 of the barrel assembly 126. The groove 154 includes a horizontal portion 156 and a vertical portion 160.
The horizontal portion 156 of the groove 154 is preferably parallel to the axis of the barrel 132 and controls the movement of the slide housing 136 during recoil of the slide assembly 102 as the pistol 100 is fired. As will be describe below, it is desirable that the slide housing 136 travel horizontally backwards and forwards during the firing cycle with respect to the frame 104 when the pistol 100 is level. Positioning the boss 152 within the horizontal portion 156 of the groove 154 restricts the motion of the slide housing 126 to be in a back and forth direction that is parallel to the axis of the barrel 132, e.g., horizontally when the barrel and pistol are level.
As is also shown, the horizontal portion 156 of the groove 154 is formed so as to be forward of the ejection port 150 and a firing pin assembly 146, which facilitates removal of the barrel assembly 126 for maintenance purposes as will be described in greater detail below. The vertical portion 160 of the groove 154 is also located forward of the firing pin assembly 146 adjacent a forward region of the ejector port 150 to facilitate removal of the barrel assembly 126 from the slide housing 136.
As shown, the vertical portion 160 of the groove is wider than the horizontal portion 156. In one specific implementation, the horizontal portion 156 of the groove 154 is 2.43 inches long and is 0.13 inches wide and the vertical portion is 0.33 inches wide. In this implementation, the boss 152 has a diameter of approximately 0.10 inches. Of course, persons of ordinary skill in the art will appreciate that the dimensions can vary depending upon the application without departing from the scope of the present invention.
Referring now to FIG. 2C, a spring return mechanism 162 is shown. The first seat 164 for the spring return mechanism 162 is formed on a bottom surface of the firing chamber 130 of the barrel assembly 126. This can comprise a standard seat such as those found on GlockTM brand pistols and can comprise a hook assembly that receives a first end of the spring return mechanism 162. A second seat 166, in the form of an opening adjacent the barrel opening 140, is formed on the slide housing 136. The spring return mechanism 162 is thus mounted between the barrel assembly 126 and the slide housing 136 such that the spring return mechanism 162 returns the slide housing 136 to a forward position after the slide assembly has been recoiled backwards when the pistol is fired. The operation of the spring return mechanism 162 is the same as spring return mechanisms understood in the art.
FIG. 2C illustrates the groove 154 and boss 152 discussed above in greater detail. As shown, in the forward position of the slide housing 136, when the pistol is ready to be fired, the boss 152 is positioned to the rear of the horizontal groove 156 adjacent a back edge 172 of the vertical groove 160. A front edge 174 of the vertical groove 160 is formed sufficiently spaced from the back edge 172, that when the shooter wishes to disassemble the barrel assembly 126 from the slide housing 136, the shooter can remove the spring return mechanism 162 and separate the barrel assembly 126 from the firing pin assembly 146 so that the back end of the barrel assembly 126 containing the firing chamber 130 can then pivot downward via the vertical groove 160. This allows the shooter to remove the front end of the barrel 132 from the barrel opening 140.
Moreover, reassembly of the barrel assembly 130 into the slide housing 136 is also greatly simplified as it does not require the removal of any slide members or interconnection of the barrel assembly to any slide members; the barrel 132 must simply be positioned within the barrel opening 140 and the boss 152 is then slid upward through the vertical groove 160 so as to be aligned with the horizontal groove 156. The spring return mechanism 162 is then positioned between the first seat 164 on the slide housing 136 and the second seat 166 on the barrel assembly 126 which then retains the barrel assembly 126 in the orientation shown in FIG. 2C.
FIG. 2D is a side perspective view of the pistol 100 incorporating one embodiment of a replacement slide assembly 102 with the slide housing 136 in the fully retracted position that permits loading of a new round into the firing chamber 130. In this embodiment, the replacement slide 102 is configured to permit a larger caliber pistol, e.g., a 9 mm or .40 caliber pistol, to shoot a smaller caliber round such as a .22 caliber round. It is understood that a .22 caliber round produces significantly less recoil than a 9 mm or .40 caliber pistol and thus the operation of the replacement slide assembly 102 must be modified to accommodate for the reduced recoil.
In one implementation, for a replacement slide assembly 102 used in conjunction with a GlockTM brand pistol, the replacement slide assembly 102 induces the barrel to remain horizontal during cycling of the slide assembly. In standard GlockTM pistols, the barrel assembly drops slightly when the barrel assembly is separated from the firing pin assembly 146 as the slide housing 136 beings to cycle. This lowers the firing chamber 130 slightly so as to permit loading of a next round 176 in a magazine 180 into the firing chamber 130 as the slide housing 136 returns to its initial position shown in FIG. 2C.
However, smaller ammunition, such as .22 caliber ammunition can produce insufficient recoil to achieve this pivoting as well as forcing the slide housing 136 back sufficiently to eject the empty shell casing, cock the trigger assembly 110 etc. So, to reduce the forces operating against the recoil of the slide assembly 102, in this embodiment, the replacement magazine 180 is positioned to sit higher into the slide assembly 102 so that when the firing pin assembly 146 is removed over the top of the magazine 180, the spring loaded magazine urges the next round into the ejection port 150 so that the round 176 is substantially co-axial with the axis of the barrel thereby permitting easier loading of the round 176.
It will be further understood that most larger caliber pistols shoot center fire ammunition and .22 caliber ammunition is rim fire. This requires that the firing pin 182 of the firing pin assembly 146 be offset from the center axis of the barrel 132 and firing chamber 130 so as to strike the rim of the .22 cartridge to fire the cartridge. FIG. 3 illustrates an example of one implementation of an offset firing pin 182 in a replacement firing pin assembly 146.
Referring now to FIGS. 4 and 5, the unique sight mounting assembly 200 will now be described. It will be apparent from the following description that this sight mounting assembly can be used in conjunction with an original slide assembly for a semiautomatic pistol, a replacement slide assembly or it can be used in conjunction with any other type of pistol or firearm without departing from the scope of the present invention.
In this specific embodiment, the rear 202 of the slide housing 136 includes a rear sight mount 120 as discussed above. In this embodiment, the rear sight mount 120 includes one or more fixed mounting components 204 that are formed in a recess 205 having a recessed surface 206 that is recessed below the level of the main surface 210 of the slide housing 136. Preferably, the mounting projections 204 comprise a plurality of mounting projections that extend in a line that intersects the axis of the barrel 132 for the reasons given below.
FIG. 5 illustrates a sight mounting plate 212 that is adapted to be positioned within the recess 205 on the recessed surface 206. As is shown, the sight mounting plate 212 has openings 214 that are sized and positioned on the plate to receive the fixed mounting components 204. The sight mounting plate 212 also defines a dove-tailed groove 216 that extends across the width of the plate 212 that is adapted to receive a fixed sight 220 (FIG. 6A). The plate 212 preferably has dimensions that match the dimensions of the recess 205 and so that the plate 212 sits flush with the main surface 210 of the slide housing 136. As shown, various weight savings or ornamental grooves 217 can also be formed in the plate 212.
The mounting components 204 can comprise projections that are hollow and can receive fasteners to secure the plate 212 into the recess. Alternatively, the mounting components 204 can be screw holes that receive screws or other fasteners to secure the plate 212 into the recess. Alternatively, the mounting components 204 can be projections that fit through the holes 214 of the plate 212 so that the plate 212 is secured in the recess 205 via friction.
Regardless of how the mounting plate 212 is secured within the recess 205, the mounting plate 212, when positioned within the recess 205, is maintained in a fixed relationship with the front sight 122 and also with respect to the axis of the barrel 132. Thus, the mounting plate 212 can be positioned within the recess 205 and secured thereto. The fixed sight 220 can then be moved laterally across the groove 216 until it is properly aligned with the front sight 122 so that the pistol 100 is sighted in. Due to the fixed arrangement of the plate 212 with respect to the axis of the barrel 132, the plate 212 can be removed and re-installed into the recess 205 and the sighting orientation of the fixed sight 220 with respect to the front sight 122 can be maintained. Thus, the sight can be switched out without requiring the shooter to re-sight the firearm.
Further, as shown in FIG. 6B, an optical sight 230 such as a Trijicon RMR, a Leupold Delta Point, an Insight MRDS etc. can also have a mounting plate 232 that is sized to fit within the recess 205 and engage with the mounting components 204 in the same manner as the mounting plate 212 described above. Thus, the recess 205 and the mounting components 204 allow for the interchangeability between multiple different sights without requiring that the sights be re-sighted to the pistol when switched back and forth.
A further advantage of the recess 205 is that with a typical optical sight 230, the height of the center of the optical sight 230 is reduced by an amount of the recess. In one implementation, the recess is 2 mils deep which results in the center point of a standard optical sight 230 being in line with the visual line of a standard fixed set of iron sights. Consequently, the sight picture of the shooter using an optical sight and an iron sight can be maintained to be closer to each other. This further allows the shooter to hold the pistol with respect to their eyes at about the same orientation regardless of which sight is being used which enhances the shooter's accuracy.
While the foregoing has shown, illustrated and described various embodiments and implementations of the present invention, it will be apparent from the foregoing description that various changes and modifications to the apparatuses described above and the uses thereof may be made by those skilled in the art without departing from the scope of the present invention. Hence, the scope of the present invention should not be limited to the foregoing discussion but should be defined by the appended claims.

## Claims

1. A slide assembly for a pistol having a frame and a trigger assembly of a first caliber comprising:
a barrel assembly with a firing chamber and a barrel defining an axis wherein the barrel assembly includes a lateral protrusion; and
a slide housing that is adapted to be positioned on the frame of the pistol for reciprocation between a forward battery position and a rearward loading position, such that the recoil of the pistol induces the slide housing to slide backwards along the frame;
wherein the slide housing defines a groove having a first section that extends in a direction parallel to the axis of the barrel; and
the groove having an upper surface and a lower surface parallel to each other and closely receiving the protrusion therebetween when the slide is in the forward position, the rearward position, and all intermediate positions therebetween.

2. The assembly of claim 1, wherein the protrusion comprises a boss.

3. The assembly of claim 1, wherein the slide housing has a forward portion that receives the barrel assembly and a rearward portion.

4. The assembly of claim 3, wherein the slide housing further includes a firing pin assembly that engages with the trigger assembly of the frame and wherein the firing pin assembly is located in the rearward portion of the slide housing.

5. The assembly of claim 4, wherein the groove has a horizontal portion and the horizontal portion of the groove is located within the forward portion of the slide.

6. The assembly of claim 5, wherein the slide housing defines an ejection port that is interposed between the forward and rear portions of the slide housing and wherein the horizontal portion of the groove is located adjacent to and forward of the ejection port.

7. The assembly of claim 1, including a vertical groove portion that extends downward from a rear end of the groove that permits the protrusion to be removed from a horizontal portion of the groove to thereby permit removal of the barrel assembly from the slide housing.

8. The assembly of claim 7, wherein the vertical portion of the groove is sized so that the
protrusion and the barrel assembly can be spaced from the firing pin assembly by
movement of the slide housing to permit the first protruding member to be removed from the
horizontal portion of the groove.

9. The assembly of claim 8, wherein the horizontal portion of the groove is approximately 2.43 inches long inches long and 0.13 inches wide and the vertical portion of the groove is approximately 0.033 inches wide.

10. The assembly of claim 1, further comprising a spring return mechanism that is detachably mounted between the slide housing and the barrel housing and wherein the spring return mechanism retains the barrel assembly in the slide housing such that removal of the spring return assembly permits removal of the protrusion from the groove and removal of the barrel assembly from the slide housing.

11. The assembly of claim 10, wherein the slide housing defines a first end where the barrel of the barrel assembly protrudes and a first seat that receives the spring return mechanism and the firing chamber housing defines a second seat that receives the spring return mechanism.

12. A pistol comprising:
a frame;
a slide connected to the flame the and operable to reciprocate between a forward battery position
and a rearward loading position;
the slide defining a central passage receiving an elongated barrel;
the barrel having a protrusion lateral to the length of the barrel; and
the slide defining a groove having a first section that extends in a direction parallel to the length of the barrel; and
the groove having an upper surface and a lower surface parallel to each other and closely receiving the protrusion when the slide is in the forward position, the rearward position, and all intermediate positions therebetween.

13. The pistol of claim 12 wherein the groove has opposed elongated upper and lower surfaces facing each other.

14. The pistol of claim 12 wherein the slide is operable to move to a disassembly position forward to the forward position, and wherein the groove has a downward segment operable for passing the protrusion when the slide is in the disassembly position.

15. The pistol of claim 14 wherein the downward segment is perpendicular to an adjacent portion of the groove.

16. The pistol of claim 12 wherein the protrusion extends horizontally from the barrel when the pistol is in a normal vertical shooting position.

17. The pistol of claim 12 wherein the barrel has a rear chamber portion including the protrusion.

18. The pistol of claim 12 wherein the slide includes a vertical sidewall when the pistol is in a normal vertical shooting position, the vertical sidewall defining the groove.