Abstract:
The present invention relates to firearms requiring the smooth operation of slidably engaged subassemblies for effecting projectile loading, maintenance, triggering, discharge, or reloading of a projectile. The major drawback of the prior art, such as that applying to slide-action pistols, is that friction occurs unevenly and at high levels between moving parts, which leads to damaging levels of frictive heat, wear, or warping, as well as jamming. The slidable guidance system proposed herein addresses this drawback by employing micro-rollers whose surfaces do not at any one point constantly touch the slidable gun part(s) with which they come in contact. Preferably, at least a set of micro-rollers and a pair of channels are installed in the inner sides of a slide and the upper outer sides of a gun frame, or on the lower face of a slide-housed slidable barrel and the upper face of a gun frame.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to firearms and toy guns requiring the smooth, low-friction operation of movable subassemblies for effecting projectile loading, maintenance, triggering, discharge, or reloading of a projectile. The slide action or “blowback” genus of gun, which features a slide that moves longitudinally back and forth relative to a barrel and a gun body, is perhaps the best known of this type of firearm. Japanese Patent No. 10220991 (Terada) is one instance of this slide-action type of gun, which is typified by the Colt Model 1911A-A1 pistol.  
           [0002]    The Model 1911A-A1 has a barrel-centering protuberance around the outer surface of a longitudinally mounted barrel, the muzzle of which extends through a barrel-alignment channel in a slide. The barrel-centering protuberance must be precisely fitted within the alignment channel. The gun is structured such that the slide and barrel move: (1) When a projectile is loaded from the magazine into a fixed position, (2) when the trigger is pulled, and (3) when the projectile is discharged. In order to make the slide and barrel move smoothly relative to each other, some degree of play must exist at the site of engagement between the barrel-centering protuberance on the barrel and the alignment channels in the slide. This play is necessary to deal with the heat expansion, longitudinal and upward movement, accumulation of contaminants, and so forth, that occur between the slide, barrel,and gun body. The major drawback of the necessity of this play is the friction that occurs unevenly and at high levels between parts while they move, which leads to various problems, such as uneven wear, stress, and noise. Additionally, the wear on parts creates fine particles that lead to the further deterioration of the action of the key movable parts and the airtightness of the propellant release valve.  
           [0003]    U.S. Pat. No. 5,654,519 (Albrecht) proposes a method that goes some way towards reducing the aforementioned problems for the interaction of barrel and slide in slide-action automatic pistols. Albrecht proposes an elastic and resilient barrel-centering protuberance installed in a groove—preferably in the form of a flexible steel ring—around the outer surface of the barrel, the muzzle of which extends through a barrel-alignment channel in the slide.  
           [0004]    However, the Albrecht invention, like its predecessors, employs non-rotating guidance means which, due to the constant contact between the unmovable surface of guidance parts and the guided movable gun parts, make it difficult for the system to reduce the aforementioned friction in order to ensure the smooth operation of slide-action guns. Albrecht, moreover, does not apply to other types of guns with similar slidably engageable subassemblies.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    What follows is an explanation of the improved means by which the present invention solves the above-mentioned problems associated with slide-action guns and other firearms with similarly functioning, slidably engaged parts. Preferably, at least a set guide members in the form of micro-rollers and a pair of guide channels are installed on a gun such as to be parallel and complimentarily engaged on the inner sides of a slide and on the upper outer sides of a gun frame, or on the lower face of a slide-housed slidable barrel and on the upper face of a gun frame.  
           [0006]    The present invention relates to firearms which, like slide-action pistols, require the smooth, low-friction operation of various movable subassemblies of a gun for effecting projectile discharge. One of the primary advantages of the micro-roller system proposed herein is that the surface of the micro-rollers do not at any one point constantly touch the slidable gun part(s) involved in projectile discharge with which they are in contact. Hence, when the micro-roller sliding system is installed in a gun, the sliding and rotating surfaces mutually engaged in the process of projectile discharge do not experience the aforementioned damaging levels of frictive heat, wear, or warping, as well as jamming. With extensive use, waste material may collect on the guide rollers, obstructing roller rotation. In such a case, the guide rollers can be easily removed and replaced.  
           [0007]    The present invention has a broad and flexible application. For example, the slidable unit can comprise a slide or a barrel of a pistol; a breech cylinder or a breech piston of an automatic or semi-automatic machine gun; a receiver or a bolt of an automatic rifle; or, a bolt of a bolt action rifle. In the case of an automatic or semi-automatic machine gun with a rack gear, such as that discussed in more detail below, guide rollers are preferably directly installed partially or fully into the inner surface of a breech cylinder (slidable unit) in order to guide a breech piston (slidable unit). Although the function of the parts differs from those in the machine gun described herein, it is even possible to install the micro-rollers in the cylinder of an automatic slide-action pistol to guide the piston it houses (FIG. 1). In the case of an automatic rifle, it is preferred that guide micro-rollers are installed on a receiver for the purpose of guiding a bolt (slidable unit). For bolt action rifles, it is preferred that guide rollers are installed on a frame for the purpose of guiding a bolt (slidable unit).  
           [0008]    The guide members (micro-rollers) can comprise easily removable rotational guide rollers with roller axes, or fixed guide protuberances. It is also possible to utilize roller bearings within the guide rollers, and to construct the guide rollers to be extremely small, even to the extent that micro- or nano-technology must be used to engineer them. The guide members can be attached to, or otherwise form a part of, guide rails. In addition, the guide members, or the guide members as a part of the guide rails, can rest in guide channels installed in parallel sets on or in the frame or slidable unit. Furthermore, the guide members by themselves or as a part of guide rails, can be longitudinally arranged in unlimited multiple opposing pairs on the frame or the slidable unit of the gun body. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0009]    [0009]FIG. 1 is a cross-sectional view of the various components of a toy air gun for the purpose of describing a number of the preferred embodiments of the present invention.  
         [0010]    [0010]FIG. 2 is a cross-sectional view of the slide of Embodiment No. 1, illustrating the guide rollers thereof.  
         [0011]    [0011]FIG. 3 is a lateral view sequentially illustrating the motion of the slide shown in FIG. 1.  
         [0012]    [0012]FIG. 4 is a front cross-sectional view of the slide of Embodiment No. 1, and a partial front cross-sectional view of the frame of Embodiment No. 1, illustrating the guide rollers, guide channels, and roller axes thereof.  
         [0013]    [0013]FIG. 5 is an oblique view of the gun of Embodiment No. 2, including a separated view of the slide and a sectional view of the frame, illustrating the upper part of the frame on which the guide roller and roller axes of Embodiment No. 2 are located.  
         [0014]    [0014]FIG. 6 is a view of the frame and slide of Embodiment No. 2, including a top sectional view illustrating the guide rails on the face of the frame, and a plan view outlining the guide channels in the underside of the barrel within the slide.  
         [0015]    [0015]FIG. 7 is a top sectional view of the slide of Embodiment No. 3, illustrating the guide rollers on the underside of the barrel within the slide and showing the outline of the guide channels on the upper face of the frame.  
         [0016]    [0016]FIG. 8 is a partial front cross-sectional view of the slide, barrel, and frame of Embodiment No. 3, illustrating the guide channels, guide rollers, and roller axes on the lower face of the barrel within the slide, and the guide rails and inner channels on the upper face of the frame thereof.  
         [0017]    [0017]FIG. 9 is an oblique view of the of the guide rails of Embodiment No. 4, illustrating the guide protuberances thereof.  
         [0018]    [0018]FIG. 10 is an oblique view of the guide rails of Embodiment No. 5, illustrating the guide members thereof.  
         [0019]    [0019]FIG. 11 is an oblique view of the guide rails of Embodiment No. 6, illustrating the guide members thereof.  
         [0020]    [0020]FIG. 12 is a cross-sectional view of the relevant components of a toy semi-automatic machine gun, for the purpose of illustrating Embodiment No. 7 of the present invention.  
         [0021]    [0021]FIG. 13 is a cross-sectional view illustrating the cylinder, piston, and micro-rollers of Embodiment No. 7. 
     
    
       [0022]    The parts listed below are correlated by number and name throughout FIGS.  1 - 13 . 
         [0023]    D Radius  
         [0024]    [0024] 1  Gun frame  
         [0025]    [0025] 2  Grip  
         [0026]    [0026] 3  Projectile  
         [0027]    [0027] 4  Projectile loading chamber  
         [0028]    [0028] 5  Gas chamber  
         [0029]    [0029] 6  Magazine  
         [0030]    [0030] 7  Spring  
         [0031]    [0031] 8  Gas release valve  
         [0032]    [0032] 9  Gas passage  
         [0033]    [0033] 10  Elastic nozzle  
         [0034]    [0034] 11  Barrel  
         [0035]    [0035] 12  Inner barrel  
         [0036]    [0036] 13  Projectile holding chamber  
         [0037]    [0037] 14  Slide  
         [0038]    [0038] 15  Cylinder  
         [0039]    [0039] 16  Return spring  
         [0040]    [0040] 17  Trigger  
         [0041]    [0041] 18  Hammer  
         [0042]    [0042] 19  Gas valve knob  
         [0043]    [0043] 20  Piston  
         [0044]    [0044] 27  Interlinking protuberance  
         [0045]    [0045] 28  Spring  
         [0046]    [0046] 30  Guide rail  
         [0047]    [0047] 30   a  Guide member  
         [0048]    [0048] 30   b  Inner guide channel  
         [0049]    [0049] 31  Guide roller  
         [0050]    [0050] 32  Guide channel  
         [0051]    [0051] 33  Guide protuberance  
         [0052]    [0052] 34  Roller axis  
         [0053]    [0053] 110  Piston cylinder apparatus  
         [0054]    [0054] 111  Barrel  
         [0055]    [0055] 112  Cylinder  
         [0056]    [0056] 113  Nozzle  
         [0057]    [0057] 114  Piston  
         [0058]    [0058] 115  Spring  
         [0059]    [0059] 116  Projectile  
         [0060]    [0060] 117  Loading chamber  
         [0061]    [0061] 118  Cylinder push spring  
         [0062]    [0062] 119   a  Spring post  
         [0063]    [0063] 119   b  Component  
         [0064]    [0064] 120  Gear mechanism  
         [0065]    [0065] 121  Rack  
         [0066]    [0066] 124  Pinion  
         [0067]    [0067] 127  Cogless portion  
         [0068]    [0068] 128  Gear group  
         [0069]    [0069] 129  Motor  
         [0070]    [0070] 130  Trigger  
         [0071]    [0071] 131  Switch  
         [0072]    [0072] 132  Interlocking components  
         [0073]    [0073] 133  Micro-roller  
         [0074]    [0074] 134  Rotational axis 
       DETAILED DESCRIPTION OF THE INVENTION  
       [0075]    What follows is a detailed description of the composition and operation of various embodiments of the roller sliding system of the present invention in reference to the drawings.  
         [0076]    [0076]FIG. 1 is a cross-sectional view of the normal loaded state of a toy air gun for the purpose of describing the several preferred embodiments of the present invention. FIG. 2 is a cross-sectional view of the slide of Embodiment No. 1 of the present invention. FIG. 3 is a lateral view showing the sequential motion of the slide of FIG. 1. FIG. 4 is a front cross-sectional view of the slide, and a partial front cross-sectional view of the frame, of Embodiment No. 1 of the present invention. FIG. 5 is an oblique, separated view of Embodiment No. 2 of the present invention. FIG. 6 is a top sectional view of the frame, and a plan view of the underside of the slide, of Embodiment No. 2 of the present invention. FIG. 7 is a top sectional view of the underside of the slide of Embodiment No. 3 of the present invention. FIG. 8 is a partial cross-sectional view of the slide, barrel, and frame of Embodiment No. 3 of the present invention. FIG. 9 is an oblique view of the guide rails of Embodiment No. 4 of the present invention. FIG. 10 is an oblique view of the guide rails in Embodiment No. 5 of the present invention. FIG. 11 is an oblique view of the guide rails in Embodiment No. 6 of the present invention. FIG. 12 is a cross-sectional view of the relevant components of a toy semi-automatic machine gun, illustrating Embodiment No. 7 of the present invention. FIG. 13 is a cross-sectional view illustrating the cylinder and piston of Embodiment No. 7.  
         [0077]    What follows is an explanation of the overall structure of the toy slide-action automatic pistol in FIG. 1. Referring to FIG. 1, a grip  2  of a gun frame  1  contains a removable magazine  6 , within which is fitted a projectile loading chamber  4  for housing a number of projectile  3  (plastic BBs), and a gas chamber  5  for storing pressurized gas. Pressurized air, or pressurized gas such as Freon, nitrogen, or carbon dioxide gas, can be used as a propellant in the illustrated type of pistol; in the case of FIG. 1, gas chamber  5  is filled with liquid gas. In loading chamber  4 , projectile(s)  3  is pushed upward with a spring  7 . Furthermore, an elastic nozzle  10  is fitted in the upper part of gas chamber  5  and forms a gas release valve  8  and a gas passage  9 . In its normal state, gas passage  9  is shut off by gas release valve  8 . An inner barrel  12  is fixed within a barrel  11  and acts as the passage for a discharged projectile  3 . A projectile holding chamber  13  is an elastic, cylindrical rubber chamber at the muzzle-end of barrel  11 . The inner diameter of holding chamber  13  is some degree smaller than the outer diameter of projectile  3 , such that projectile  3  is held in holding chamber  13  based on mutual counterforce. In addition, the inner surface of holding chamber  13  manifests protuberances which have a relatively smaller inner diameter than holding chamber  13  and serve to further secure projectile  3 . A slide  14  is a slidable unit involved in projectile discharge which is installed so as to cover but not directly make contact with barrel  11 , also a slidable unit involved in projectile discharge, within which is fixed an inner barrel  12 , at the rear of which are a piston  20  and a cylinder  15 , both of which are also slidable units involved in projectile discharge. Inner barrel  12  slidably holds cylinder  15 . A return spring  16  is fitted between slide  14  and gun frame  1 , and serves to pull slide  14  back to its original position after slide  14  has moved rearward.  
         [0078]    Also, gun frame  1  is furnished with a trigger  17  at the front of grip  2 , and a hammer  18 , which is linked to a trigger  17  and is placed at the back of gun frame  1 . When trigger  17  is pulled, a sear that holds in place hammer  18  moves, releasing hammer  18 , which rotates under the force of a compressed spring and strikes an impact plate; this impact plate pushes against the coil-force of a gas valve knob  19  (of a gas release valve  8 ), causing gas passage  9  to open, gas to be emitted, and projectile  3  to be discharged from the gun muzzle.  
         [0079]    In the inner rear part of slide  14 , and to the rear of inner barrel  12 , are fitted piston  20  and cylinder  15 , which are mounted so as to be slidable relative to one another. At the upper portion of cylinder  15  is positioned an interacting protuberance  27 , which interacts with slide  14  such that interacting protuberance  27  moves when slide  14  moves rearward. A spring  28  is installed between interacting protuberance  27  and slide  14 .  
         [0080]    In Embodiment No. 1 of the present invention, as illustrated in FIG. 2, guide rollers  31  are mounted longitudinally in the inner left and right sides of slide  14  to guide slide  14 , which, as illustrated in FIG. 3, can move in an alternating longitudinal direction on gun frame  1 . Furthermore, as shown in FIG. 4, guide channels  32  are made in the outer left and right upper sides of gun frame  1  such that guide rollers  31  are directly slidably engaged with guide channels  32 ., where they on roller axes  34 . Each guide roller  31  has a centering roller axis  34  on which it rotates freelyy. In Embodiment No. 1, roller axis  34  takes the form of a metallic guide post embedded perpendicularly into the lower inner surface of slide  14  such as to extend perpendicularly into guide roller  31  from slide  14 .  
         [0081]    In addition, guide rollers  31  can be mounted at any point along the inner left and right sides of slide  14 . It is further possible, for the purpose of stably guiding the relative movements of the barrel and the slide, to directly mount on barrel  11  or slide  14  similar micro-rollers at points along the gap between the outer surface of barrel  11  and the inner surface of slide  14  so as to stably guide both parts. Also, guide roller  31  is constructed to be removable. With extensive use, waste material may collect on guide roller  31 , obstructing roller rotation. In such cases, guide roller  31  can be removed and replaced with a new one. The efficiency of guide roller  31  can be increased by utilizing roller bearings within it.  
         [0082]    In Embodiment No. 2 of the present invention, as illustrated in FIG. 5, guide rollers  31  are mounted at two parallel points on the front end and two parallel points on the back end of guide rails  30 , which are mounted on gun frame  1 . Slide  14 , then, is secured and stabilized at these four longitudinal, left and right points. Guide channels  32 , which are engaged with guide rails  30  via guide rollers  31 , are furnished longitudinally and parallel on the inner left and right sides of slide  14 , as shown in FIG. 5 and FIG. 6. Thus, the guide rollers  31  on guide rails  30 , in interaction with guide channels  32 , serve to guide slide  14 , which, as illustrated in FIG. 3, can move longitudinally on gun frame  1 . However, it is also possible to make the guide channels on the lower face of barrel  1 , which is housed within slide  14 ; or, to make guide channel  32  out of recesses made on both barrel  1  and slide  14 .  
         [0083]    In Embodiment No. 2, to mount guide rollers  31 , a portion of guide rail  30  is machined into a cylindrical shape which thrusts upwardly as a centering roller axis  34 , which takes the material form of a guide post perpendicular to frame  1 . Guide roller  31  is set so as to rotate on roller axis  34 . The outer edge of guide roller  31  is configured to protrude more than the outer-edge surface of guide rail  30 , and to abut the inner surface of guide channel  32 , which is formed on the inner surface (plan view) of slide  14 .  
         [0084]    In Embodiment No. 2, referring to FIG. 1, FIG. 5 and FIG. 6, slide  14  slides on guide rollers  31  of guide rails  30  when projectile  3  is readied for firing, and when trigger  17  is pulled, projectile  3  is discharged and the next projectile  3  is positioned in projectile holding chamber  4 . Thus, guide channels  32  have points of contact with, or are in a consistent line of contact with, guide rollers  31 . The remaining, non-contact area, that is, the gap between guide rails  30  and slide  14 , can be made large or small.  
         [0085]    Referring to FIG. 7 and FIG. 8, Embodiment No. 3 illustrates a means by which to mount guide rollers  31  (and guide rails  30 ) on barrel  11  instead of on gun frame  1  or on slide  14 . In this case, guide rails  30  are machined longitudinally and parallel into the left and right sides of the upper surface of gun frame  1 , but guide rollers  31  are not mounted on guide rails  30 ; rather, guide rollers  31  are supported and centered by axes  34  made in the form of guide posts which are installed supsended in left-right pairs downward from the underside of the surface of barrel  11 , which is slidably housed within slide  14 . The lower, lateral inner surfaces of slide  14 , and inner channels  30   b  on the lower, outer lateral surfaces of guide rails  30 , form guide channels  32  which engage guide rollers  31 . Also, the lower surface of barrel  11  is somewhat cut away in order to provide clearance space for guide rails  30  as well as the posts of guide axes  34 . As shown in FIG. 8, guide rollers  31  are installed so as touch inner guide channels  30   b.  In this case, as well, the number and positioning of guide rollers  31  is not limited to the illustrated embodiment.  
         [0086]    Next, in Embodiment Nos. 4-6, several types of guide members which can be mounted on the above-mentioned guide rails  30  are discussed. Referring to FIG. 9, in Embodiment No. 4, in place of guide rollers  31 , the guide rail components employed are fixed concave slide guide components. Namely, slide guide components made of plates of curved metal (or other substance) are secured to the outer sides of guide rails  30 . The radius of a curved guide protuberance  33  is designed to be slightly larger than the gap between guide rail  30  and guide channel  32 . Guide protuberance  33  have points of contact or a constant line of contact with guide channels  32  and is guided on the inner surface of guide channels  32 . In the case of a slide guide component with this type of configuration, it is possible for guide protuberance  33  to change its shape in order to correspond to any changes in the gap between guide rail  30  and guide channel  32 , thus allowing for stable guidance and the prevention of instability. It is preferred that such a guide protuberance be made out a low-friction, slippery plastic or metal alloy.  
         [0087]    Next, Embodiment No. 5 is discussed using FIG. 10. In Embodiment No. 5, space is made in guide rail  30  for a guide member(s)  30   a  in the form of a guide roller, cylindrical protuberance, or steel sphere, etc., a part of which is designed to protrude from the lateral surface of guide rail  30 . A guide member  30   a  is configured so that it is in contact with guide channel  32 . The number of guide members  30   a  to be furnished on guide rails  30  is not limited by the present illustration; a large or small number of guide members  30   a  can offer stable guidance.  
         [0088]    Embodiment No. 5 illustrates the design of a guide member  30   a  for guiding the lateral surface of a guide rail  30 , while Embodiment No. 6 shows, with reference to FIG. 11, guide member  30   a  in the form of either a guide protuberance or a guide roller which can be furnished on both the lateral and the upper surfaces of a guide rail  30 , making it even more possible to assure stable vertical and horizontal positioning and guidance during projectile discharge parts&#39; sliding actions.  
         [0089]    In regards to Embodiment Nos. 1-6, it is not necessary to limit the positioning of guide rollers  31 , guide protuberances  33 , or guide members  30   a  to certain mounting positions or to a given number of points. It is possible to mount a pair of guide rollers  31  on both left and right guide rails  30 , and to mount such a left-right pair of guide rollers  31  longitudinally and in multiple pairs along guide rails  30 . Furthermore, instead of mounting pairs of guide rollers  31  on both left and right guide rails  30 , it is possible, as illustrated by FIG. 10 and FIG. 11, to install elastic, slippery guide members  30   a  in the form of protuberances or rollers on both the left and right as well as on the upper surface of guide rails  30 , with no guide posts extending perpendicularly into such guide members. Moveover, slide  14  can be stably guided by mounting multiple guide rollers in longitudinal guide positions, and even over six of such guide rollers or guide members can be mounted, with or without guide rails. In fact, concerning the guide components of Embodiment Nos. 2, 3, 5, slide  14  can be stably guided by longitudinally mounting as many guide rollers  31  or guide members  30   a  as possible on both the left and right guide rails  30 . Also, in all of the relevant aforementioned cases, the guide roller units can be extremely small, even to the extent that nanotechnology can be used to engineer them. Preferably, guide rollers  31  are at least mounted on the front and back inner surface of the parallel sides of slide  14 , on the upper front and back face of gun frame  1 , or on the lower front and back face of barrel  11 .  
         [0090]    The technical scope of the present invention is not limited to toy guns; it applies to all small firearms which feature movable subassemblies involved in projectile discharge, such as an automatic pistol&#39;s slide and barrel, a machine gun&#39;s breech cylinder and piston, a bolt-action rifle&#39;s receiver and bolt, or other interactive slidable units. To further illustrate the versatility of the application of the present invention, the following embodiment provides an example of the present invention applied to a toy semi-automatic machine gun which employs a rack gear.  
         [0091]    Referring to FIG. 12, piston-cylinder apparatus  110  is furnished at the rear (opposite the muzzle-end) of a barrel  111 . It is possible for pressurized air to be emitted towards barrel  111  from a nozzle  113  located at the forward end of a cylinder  112 . A piston  114  is installed within cylinder  112  to be slidable in a longitudinal, forward and rearward direction. The pressure of a spring  115  on piston  114  is in a direction which generates compressed air in cylinder  112 . Cylinder  112  itself, which is pushed by a cylinder push spring  118 , is mounted to be longitudinally slidabe, which permits a projectile  116  to enter a loading chamber  117 . Therefore, both piston  114  and cylinder  112 are slidable units involved in projectile discharge  
         [0092]    Spring  115 , secured on the rearward end of a spring post  119   a,  governs the compressing action of piston  114 , which receives and supports the forward end of spring  115 . Piston  114  features a component  119   b,  which faces in a forward direction from the rearward end of piston  114  where a rack  121  is furnished as part of a gear mechanism  120 . A pinion  124 , which is another element of gear mechanism  120 , is positioned to engage with rack  121 . The driving force of a motor  129  is transmitted via a gear group  128  to pinion  124 . In order for the gear pressure of gear mechanism  120  to be properly recieved, pinion  124 , without axial deflection, and rack  121 , without curving, are both designed to advance in a straight line.  
         [0093]    When a trigger  130  is pulled, a switch  131  is activated and motor  129  begins to rotate, after which pinion  124  and rack  121  are in a state of engagement and are able to rotate. Furthermore, when pinion  124  rotates and advances to a cogless portion  127 , piston  114  rapidly moves forward under the projecting pressure of spring  115 , compressing the air cylinder  112 . The compressed air thus produced is emitted from nozzle  113 , discharging projectile  116  if one is present in loading chamber  117 . After this process of projectile discharge, cylinder  112  is temporarily brought back due to the interlinking of cylinder  112  with interlocking components  132 , which consist of a cam, etc., installed on gear group  128 . Also, a single projectile  116  in the loading channel is loaded into loading chamber  117  by pushing spring  118 .  
         [0094]    In the case of this type of gun, as illustrated in FIG. 13, the installation of numerous micro-rollers  133  in the area of the gap between piston  114  and cylinder  112  in the gun frame enable the smooth sliding and precise alignment of piston  114 . The rotational axis  134  of roller(s)  133  is fixed on the inner circumference of cylinder  112  such that the outer surface of roller(s)  133  is in contact with the outer surface of piston  114  within cylinder  112 . In Embodiment No. 7, micro-rollers  133  are installed at 120 degree intervals on cylinder  112 . However, even more micro-rollers  133  can be installed, and neither the number nor the positioning of micro-rollers  133  is limited by the description of the preferred embodiment described herein.  
         [0095]    The preferred embodiments of the present invention have been described above. The drawings presented herein are intended to illustrate the preferred embodiments of the invention but they should not be considered a limitation of the present invention. Therefore, modifications, adaptations, or other changes concerning the illustrated art may fall within the spirit and scope of the present invention.