Abstract:
A dummy cylinder for a revolver that permits dry fire practice but does not permit the insertion of live ammunition. The dummy cylinder approximately duplicates the outer dimensions of a normal cylinder so that it may replace the normal cylinder for safer training. It may use the extractor and ratchet of the revolver or may be constructed to simulate the dimensions of those parts. It may contain integral firing-pin cushioning devices, or may be constructed to allow the insertion of such devices while preventing the insertion of live ammunition.

Description:
BACKGROUND 
     It is well known in the art of firearms marksmanship to practice by “dry firing.” This is the actuation of the trigger and firing mechanism without the use of live ammunition. When performed with due care, it is a safe means to gain familiarity and “muscle memory” that improves accuracy at low cost. Products known as “snap caps” are sometimes used to simulate the presence of ammunition and thus avoid any damage to the firearm that might occur. These devices have the approximate external shape of live ammunition and thus may be inserted into the chamber before practicing, but inside contain a small plunger and a spring that absorb the shock of the firing pin as a primer might. 
     However, firearms users do not always exercise due care. Sometimes live ammunition is placed in the chamber rather than a snap cap. As a result, the firearm may be discharged unintentionally, posing a significant risk of injury or death. In addition, there is no easy way for someone to confirm visually that snap caps are inserted rather than live ammunition. Thus, for instance, while and instructor might wish to have students conduct dry fire drills in a classroom rather than on a firing range, doing so tends to encourage the violation of fundamental safety rules because it involves pulling the trigger of a firearm without a proper bullet-absorbing backstop. 
     Other forms of practice, such as drawing from a holster or drawing from concealment, are also potentially dangerous if attempted without proper attention to the unloading of the firearm. 
     Special devices which simulate both the external dimensions of firearms, which are useful for practicing drawing from a holster or conducting retention and takeaway drills with a partner, do exist. In addition, some manufacturers produce devices that simulate both the appearance and the operation of particular firearms, but which do not permit ammunition to be inserted, to allow the experience of dry firing in safety. However, the cost of such dummy guns is often prohibitive for the average person. In some cases the dimensional fidelity of dummy guns can be questionable, which can mean that, for instance, drawing a plastic casting of a gun from a holster can be a very different experience than drawing the real thing, and therefore encourage the development of bad habits. Thus such tools are often limited to law enforcement or military agencies with sufficiently large budgets and competent armory staffs to ensure proper operation and training value. 
     SUMMARY 
     A replacement cylinder for a revolver which is incapable of receiving live cartridges and which may optionally integrate a mechanism for cushioning the firing pin of the revolver. 
    
    
     
       DRAWINGS 
         FIG. 1  is an exploded view of a revolver&#39;s cylinder showing the parts of a functional firearm and a live cartridge intended for use in that firearm. 
         FIG. 2  is a perspective view of one embodiment of a dummy cylinder intended to permit safe practice and training, which receives the ratchet and extractor of the revolver into its back end, and with chambers sized to receive certain types of snap caps as shown, but not live cartridges. 
         FIG. 3  is a perspective view of an alternative embodiment of a dummy cylinder which incorporates a non-functional extractor and a ratchet integrally into its back end, with an integral firing pin cushioning mechanism that cannot be removed shown in exploded view. 
         FIG. 4  is a perspective view of still another embodiment of a dummy cylinder which has a completely solid back end where chambers would normally be located. 
         FIG. 5  is a perspective view showing the cylinder of a functional firearm, with openings on the front face to allow a bullet to be fired. 
         FIG. 6  is a perspective view of an embodiment of a dummy cylinder with small holes in the front face to facilitate accurate manufacturing. 
         FIG. 7  is a perspective view of an embodiment of a dummy cylinder with a smooth front face. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of this application, the term “firing cylinder” shall be used to refer to that part of a functioning revolver that contains chambers intended to receive ammunition for the purpose of firing. This term is used to differentiate the cylinder, as it is usually known in the art, from the “dummy cylinder” that is the subject of this application. 
       FIG. 1  shows a exploded view of a firing cylinder  10 , extractor  12 , ratchet  14 , crane  16  with pivot tube  18 , and center rod  20  taken from an ordinary double-action revolver, as is well known in the art. The cylinder  10  has chambers  22  which receive cartridges  24  for firing. In use, the firing cylinder  10  rotates about pivot tube  18  when the hammer is cocked or the trigger is pulled in order to place a fresh cartridge in front of the firing pin. When struck by the firing pin, the primer  26  detonates, igniting the gunpowder and propelling the bullet  28  out of the firearm. 
     When a user wishes to practice pulling the trigger without actually firing a round, it is common to insert action proving dummies, or “snap caps”  23  into the chambers  22 . These devices are intended to simulate the presence of the primer  26  to prevent possible damage to the firing pin. A snap cap  23  has external dimensions that simulate those of a live cartridge  24  to allow it to sit snugly in the chamber  22 . 
     In order to prevent the accidental placement of live ammunition in the chamber  22  and the subsequent discharge of the firearm, it is desirable to replace cylinder  10  with non-firing dummy cylinder  30 , as shown in  FIGS. 2-4 and 6-7 . Dummy cylinder  30  is designed to take the place of cylinder  10  in all respects. It has an external dimensions that closely match the relevant external dimensions of cylinder  10 . For instance, diameter  33  must be close to those of cylinder  10 , and the location of stop notches  34  must also match those of the original, and the placement of flutes may be necessary to facilitate installation. The length  32  may be similar to that of the firing cylinder  10 , or may be substantially shorter, and thus the length  32  is not a “relevant” external dimension except to the extent that it must not be too long. The dummy cylinder  30  must have a hole  35  passing along axis  37  to accommodate pivot tube  18  and permit the dummy cylinder  30  to be mounted on the revolver. In one embodiment, best shown in  FIG. 2 , the dummy cylinder  30  is intended to be used in conjunction with the extractor  12  and ratchet  14 , and thus must have the back end  36  configured to receive them. In another embodiment, best shown in  FIG. 3 , a close facsimile  38  of the extractor  12  and ratchet  14  are formed integrally onto the back end  36 . 
     The internal dimensions of the dummy cylinder  30  are very different from those of cylinder  10 . For safety reasons, it is essential that it be impossible to insert cartridges  24  into dummy cylinder  30 , and therefore the dummy cylinder  30  must not have chambers  22  large enough to receive live ammunition of the type intended for use in the revolver. It is possible to make dummy cylinder  30  completely solid, with a smooth front end  40  (as shown in  FIG. 7 ) and with no openings  44  at all in back end  36  (as shown in  FIG. 4 ). It is also possible to have a small holes  43  in the front end  40 , as may be necessary to facilitate removal of a plastic part from a mold used in its formation. In alternative embodiment, best shown in  FIG. 2 , the chambers  22  are replaced with smaller openings  44  meant to receive snap caps  23 . Certain brands of snap caps  23  are made with dimensions smaller than those of live cartridges, and therefore an opening  44  can be devised that receives snap caps  23  but not live cartridges  24 . This is not, however, the most preferred way to make the cylinder, because it may still be possible to insert cartridges  24  of a smaller caliber than intended for the revolver into these openings  44 , which could pose a risk of explosion. 
     In a most preferred embodiment, best shown in  FIG. 3 , the dummy cylinder  30  has a firing-pin-cushioning mechanism  46  integrally and permanently placed where the chamber  24  would normally be. In this embodiment, the external dimensions of the dummy cylinder  30  are intended to simulate the relevant external dimensions of firing cylinder  10  with cartridges  24  fully inserted into it. The relevant external dimensions in this case thus include not only those of firing cylinder  10 , but also the exposed rim  45  of cartridge  24 . In one embodiment, dummy rim  47  is integrally formed onto dummy cylinder  30 . It is also possible to omit the dummy rim  47  provided that the plug  54  is designed to properly simulate rim  45 . The firing-pin cushioning mechanism  46  comprises a spring  48 , a plunger  50 , a cavity  52 , and a plug  54 .  FIG. 3  shows an exploded view of the mechanism  46 . The spring  48  is placed in the cavity  52 , and then plunger  50  is placed inside of it. Flange  58  causes plunger  50  to compress the spring when urged towards the front end  40 . Plug  54  is placed over plunger  50  and inserted into cavity  52 . The plug  54  is designed to lock into the cavity by some means. This may be elastic mechanical means, such as a clip or a raised ridge (not shown), or it may be a chemical means such as adhesive or solvent-welding. It could also screw in. These options are well known to makers of snap caps. Plug  54  has a hole  56  which permits the plunger to pass through, but which is too small for the flange  58 . Thus, the plunger  52  is exposed where it may be struck by the firing pin, and move forward, compressing spring  48 , thus simulating the presence of a primer. 
     One mechanism  46  is placed in the dummy cylinder  30  for each of the chambers of cylinder  10 . Thus, when dummy cylinder  30  is placed on the revolver, it functions as though a snap cap had been inserted into each chamber  22 . 
     Preferably, the dummy cylinder  30  is has a color that differentiates it from cylinder  10  immediately. A common “safety” color is blaze orange, such as is worn by hunters and highway workers. Such a bright color instantly tells anyone who can see the revolver that it does not contain a firing cylinder  10 , and therefore cannot fire. Blue and red are also conventionally used for dummy guns and therefore may be appropriate as well. The dummy cylinder  30  may be constructed of a material that is entirely one color, or may be painted. It is not necessary for the dummy cylinder  30  to be a solid color; a stripe or other pattern may also be used. 
     The dummy cylinder  30  can be produced from any convenient material. Polymers such as plastic or hard rubber are preferred because they are inexpensive to mold to the correct shape and easy to color. Where durability is a concern, metals may be preferred. Plunger  50  is conventionally constructed of brass, which is soft enough not to damage firing pins but hard enough to withstand repeated impacts. Plug  54  is may be constructed of the same polymer as dummy cylinder  30  so as to be compatible with the same adhesives. It may also be of a different polymer, as may be advantageous when using a clip mechanism to provide sufficient resilience. It could also be formed of metal, such as brass, to increase durability or allow for greater dimensional precision. However, the choice of material for any of these parts is not critical.