Abstract:
A cartridge follower for pushing against cartridges in a tubular magazine of a shotgun. A front face of the follower has at least one forwardly protruding member offset from the center of the front face to be tactilely distinguished from a cartridge in the magazine, but which cannot contact a central primer of a backwards cartridge. A method for determining whether a shotgun is empty includes providing such a follower in the magazine, inserting a finger into the outfeed end of a magazine, and attempting to feel the protruding member.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a cartridge follower for a tubular magazine for a firearm, and in particular to such a follower that can be identified easily by touch. 
     Repeating shotguns use tubular linear magazines in which cartridges, also called shells, are stacked one behind another in the magazine. A spring loaded follower at the front end of the magazine pushes back against the front of the first cartridge loaded into the magazine, which will be the last cartridge actually loaded into the chamber of the shotgun. The follower urges the cartridges rearwardly into position to be fed one by one into the chamber. In the past followers have usually had a flat face that contacts the front of a cartridge. 
     Without operating the loading mechanism, the only way to tell reliably when the magazine of a typical repeating shotgun is empty is to examine the firearm visually. However, this is often impractical. Police and military shotguns are often used under adverse conditions such as at night or when visibility is poor, when it would be dangerous or impossible to visually examine the shotgun. 
     Many shotguns employ a lifter which elevates each cartridge into alignment for being pushed into the chamber. Between rounds or while the shotgun is being loaded, a finger can be inserted past the lifter to the rear of the magazine, and the next cartridge in the magazine to be loaded, or the follower, can be touched. If the follower and the primer of a cartridge could be distinguished by touch, a user could determine whether a shotgun magazine was empty or not. Because police and military shotguns are often used at night or when visibility is low, a follower that can be distinguished from a shell by touch would be particularly useful to indicate whether the firearm magazine is loaded. 
     Therefore, several attempts have been made in the past to provide a follower which can be distinguished definitely from a shell by touch. Such a follower should be distinguishable by touch even when the user is wearing gloves, because police and military firearm users frequently wear fire-resistant gloves. 
     One such previously-known follower  10  has a small raised bump  12  in the center of the face of the follower as shown in FIG.  1 . The bump  12  allows a user to distinguish the follower  10  from a cartridge by touch to determine whether the magazine is empty. However, such a centrally located bump  12  has a significant disadvantage. If a shotgun shell were placed backward in the magazine by mistake the bump  12  of the follower would press on the percussion-operated primer located in the center of the base of the shotgun shell, resulting in the risk that the follower could fire the shell in the magazine, causing significant damage and risk of serious injury. 
     Another prior art follower  14 , shown in FIG. 2, has a protruding small end  16  of a central rod surrounded by a deep annular cavity  18 . However, it has been found that when a shotgun is employed in field conditions the annular cavity  18  can fill with foreign material and make the end  16  difficult to distinguish from a cartridge by touch. This follower  14  also has the disadvantage of being capable of firing a misloaded shell in the magazine because of the protrusion of the end  16  of its centrally located rod. 
     Another prior art follower  20 , shown in FIG. 3, includes a flat circular protrusion centrally located on the face of the follower  22 . The circular protrusion has a diameter of 9.53 mm, and protrudes from the face of the follower 0.89 mm. While such a protrusion is unlikely to set off the primer of a cartridge loaded backwards into the magazine, it is also too broad to be easily distinguishable from a cartridge by touch. 
     Therefore, what is still needed for a shotgun magazine is a cartridge follower that can be distinguished easily from a shell by touch, but which cannot easily fill with foreign material or accidentally discharge a shell inadvertently loaded backwards into the magazine. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the drawbacks of the prior art by providing for use in a shotgun magazine a follower that can be distinguished from a shell by touch but which cannot inadvertently discharge a shell loaded backwards in the magazine. The invention provides a follower for pushing against cartridges with a front face that has at least one protruding member offset from the center of the face. The follower thus is easily identifiable by touch, but cannot fire a shell inadvertently loaded backwards into the magazine. 
     In one preferred embodiment of the invention the follower has at least two protruding members each located far enough from the center of the front face to avoid contact with the primer of a shell loaded backward in the magazine. 
     The present invention also provides a method for determining whether a shotgun magazine is empty by providing, in the magazine, a cartridge follower with a front face for pushing against cartridges which has at least one protruding member offset from the center of the front face, and determining whether the magazine is empty by inserting a finger into the outfeed end of the magazine and attempting to feel the protruding member of the follower. 
     The invention thus allows the user of a shotgun to distinguish by feel between the follower of the magazine cartridge and a shell remaining in the magazine, thereby determining whether or not he or she needs to reload and whether the firearm is safe to be transported. This determination can be made at night or under conditions of low visibility such as are often encountered by police and military shotgun users. The determination can be made regardless of whether the breech of the shotgun is open or closed, making the invention particularly valuable for police or military users who may be endangered unnecessarily if they run out of ammunition or mishandle a loaded firearm believed to be empty. 
     The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is an isometric view of a prior art follower for the magazine of a shotgun such as that shown in FIG.  4 . 
     FIG. 2 is an isometric view of another prior art follower. 
     FIG. 3 is an isometric view of a further prior art follower. 
     FIG. 4 is a side view of a police or military style repeating shotgun with a long tubular magazine. 
     FIG. 5 is a partially cutaway view of a portion of the shotgun shown in FIG. 4 showing a cartridge follower in the magazine which is a preferred embodiment of the present invention. 
     FIG. 6 is an isometric view of the cartridge follower shown in FIG.  5 . 
     FIG. 7 is a partially cutaway view of the follower shown in FIGS. 5 and 6. 
     FIG. 8 is an isometric view of a follower that is an alternative preferred embodiment of the invention. 
     FIG. 9 is an isometric view of yet a further alternative preferred embodiment of the invention. 
     FIG. 10 is an isometric view of a follower that is an alternative preferred embodiment of the invention. 
     FIG. 11 is a partially cutaway view of a portion of the shotgun shown in FIG. 4, equipped with a follower according to the invention, showing a shell being loaded. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings which form a part of the disclosure and wherein like numerals refer to like elements, FIG. 4 shows a military or police type shotgun  24  with a long tubular linear magazine  26  capable of holding up to ten shells. The present invention is particularly useful in such a shotgun because of the greater capacity of the magazine  26  and the adverse conditions under which such shotguns are employed. 
     Referring to FIG. 5, a follower  28  which is one preferred embodiment of the invention is shown in the tubular magazine  26  of the shotgun. The follower  28 , also shown separately in FIGS. 6 and 7, is located within the magazine  26 , with the peripheral surfaces  30  of a generally cylindrical body portion  32  in easy sliding contact with the interior surfaces  34  of the magazine  26  keeping the follower  28  oriented within the magazine. The length  31  of the generally cylindrical body portion  32 , for example, may be  12  mm so as to provide a fairly large peripheral surface  30  to stabilize the follower  28  in the magazine  26 . An end of a compression spring  36  fits around a smaller diameter rear end section  38  of the follower  28  and is used to urge the follower  28  rearward in the magazine  26  to exert pressure on a shell within the magazine. 
     The follower is accessible to touch between the loading of shells as may be seen in FIG. 5, since the lifter  40 , which is normally in a down position and blocks access to the magazine and chamber, can be pushed up with a finger, permitting access to the magazine and the follower. To determine whether the magazine  26  is empty, a person using the shotgun  24  inserts a finger or thumb under the lifter  40  and into the outfeed end  42  of the magazine  26  to try to contact and feel the protrusions  44  located on the face  46  of the follower. 
     The face  46  defines a base plane  48  and has one or more protrusions  44  which extend from the base plane  48  toward any cartridge present in the magazine. The face  46  surrounding the protrusions  44  is flat and smooth, resisting the accumulation of foreign debris. The height  45  of the protrusions  44  relative to the base plane  48  may be in the range of 0.5 mm to 1.5 mm and preferably approximately 1 mm, since a height  45  greater than 1.5 mm may damage a cartridge, and a height  45  less than 0.5 mm may be too small for the protrusions to be felt easily. A center portion  50  of the face  46 , indicated by a broken line, is preferably free of protrusions except to the extent that any protrusion is of a height no greater than that of other protrusions located outside the center portion. If any centrally located protrusion has a height no greater than that of at least one protrusion located outside the center portion, the off-center protrusion will prevent the centrally located protrusion from firing a shell inadvertently loaded backward in the magazine. The diameter  51  of the center portion  50  should be at least 5 mm and may preferably be between 7 mm and 10 mm because the primer exclusive of its retaining shell of a typical shotgun shell is approximately 5 mm in diameter. A center portion  50  free of protrusions that is 7 to 10 mm in its diameter  51  insures that no protrusion can contact the primer and discharge the shell. 
     The smaller diameter rear portion  38  of the follower  28  fits inside the spring  36  freely enough for the spring to extend easily, and preferably has a length  55  great enough to encounter the far end of the magazine and prevent the spring from being damaged by an attempt to load too many shells. The protrusions  44  are spaced apart from each other around the center portion  50 . In the follower  28  shown in FIGS. 5,  6  and  7  there are four generally cylindrical similar protrusions  44 . 
     In the follower  28  the surface of the smaller diameter rear section  38  of the follower, together with the rear end of the large diameter body section  32 , defines a circumferential groove  70 . The groove  70  allows more room for the compressed spring  36 , in order to better accommodate a full magazine while not decreasing the peripheral surface area  30  of the large diameter body section  32  of the follower  28  in contact with the interior surface of the magazine  34 . 
     Alternatively, in the follower  54  shown in FIG. 8, there are only three protrusions  44 , and the length  53  of the smaller diameter rear portion  52  is shorter than the length  55  of the smaller diameter rear portion of the follower  28  shown in FIG. 6 so that the follower can be used in a magazine of smaller capacity. 
     FIG. 9 shows a follower  56  which is an alternative embodiment of the invention and has one annular protrusion  58 , or ring, located on the face of the follower  46 . The annular protrusion  58  has an interior diameter  60  of at least 5 mm, larger than the primer of a shotgun shell, and surrounds but does not occupy any of the central portion  50  of the front face  46  of the body  32 . The interior diameter  60  may, for example, be in the range of 8 mm to 10 mm and in the follower  56  is about 9 mm, which is large enough to be felt definitely as being different from the essentially flat base  62  of a shell  64 , shown in FIGS. 5 and 11, yet the outside diameter  59 , for example, 10 mm to 18 mm, of the annular protrusion  58  is noticeably smaller than that of the crimped edge of the front of a shell  66  so as not to confuse the follower with a cartridge loaded backwards. The radial width  68  of the annular protrusion  58  is preferably in the range of 1 mm to 4 mm so that the ring  58  can easily be felt but is sturdy, and in one preferred embodiment of the invention the radial width is about 2 mm. The annular protrusion  58  has a height  70  similar to the height  45  of each protrusion  44 . 
     Protruding members  44  may be roughly cylindrical as shown in FIGS. 6,  7  and  8  or may have another shape, such as shown in FIG. 10, in which the follower  66  has frusto-conical protrusions  72 . Protrusions may also be bullet-shaped or hemispherical (not shown). 
     As shown in FIG. 11, during the loading process, the lifter  40  elevates a shell  64  into alignment with the breech. During this time the follower  28 , or the rearmost one of any shells remaining in the magazine, is exposed and can be readily felt and identified by inserting a finger or thumb into the outfeed end  42  of the magazine  26 . 
     The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.