Abstract:
The present invention embodiments provide a barrel component with the forward under-portion of the barrel configured in various manners. For example, the configurations may include an upward displacement, or angular or radial contouring, of barrel material at the forward underside of a barrel component understation or projection. These configurations provide clearance to allow the barrel to bypass frame-mounted impediments to blank-fire, and permit proper timing and coordination of rearward barrel motion under impact of the recoiling slide and the resultant barrel drop into recoil position without interference with, or re-capture by, the reciprocating slide component. In addition, the blank-fire barrel may be configured to incorporate a laser device for marksmanship training and conducting realistic tactical training exercises.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 60/905,033, entitled “Blank-Firing Conversions for Semiautomatic Pistols and Method of Repetitive Blank Fire” and filed Mar. 6, 2007, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention embodiments generally pertain to firearms. In particular, the present invention embodiments pertain to semiautomatic breech-locked, recoil-operated pistols configured to produce reliable and repetitive blank-fire operation. 
         [0004]    2. Discussion of Related Art 
         [0005]    Conventional semiautomatic pistols designed to discharge high-pressure cartridges (e.g., 9 mm Parabellum, 0.357 SIG, 0.40 S&amp;W, 10 mm, and 0.45ACP cartridges) typically employ a breech-locked, recoil-activated mechanism that is derived from the BROWNING and COLT/BROWNING family of firearms. In this mechanism, the pistol barrel and slide are locked together and collectively travel rearward for a predetermined distance in response to firing of a projectile or bullet to initiate a firing cycle. The firing cycle is automatically performed from the recoil energy and typically includes: opening of the pistol breech after firing the shot; extraction and ejection of an empty cartridge shell; cocking of the pistol hammer; presentation and introduction of a loaded cartridge into the pistol barrel; and closing of the pistol breech. The design of the recoil-activated mechanism has evolved and is employed by various pistols (e.g., those produced by BERETTA, GLOCK, HECKLER &amp; KOCH, SIG-SAUER, and SMITH &amp; WESSON). 
         [0006]    In accordance with this design (and variants thereof), safe discharge of the cartridges is accomplished by delaying opening of the pistol breech mechanism (and subsequent extraction of a fired cartridge case from the barrel chamber) until the fired projectile or bullet has exited the muzzle. This relieves the high-pressure gases contained within the barrel bore that would otherwise cause catastrophic rupture of a partially extracted case lacking support of a surrounding chamber enclosure. In order to provide the breech-opening delay, the pistol barrel and slide are locked together by a mechanical mechanism, and recoil in unison for a predetermined distance until a safe level of pressure is achieved subsequent the bullet&#39;s exiting the barrel. At this point, the barrel and slide are separated through the interaction of a supporting frame abutment that engages a provision at an underside of a barrel element, thereby drawing the barrel from a locked battery position and allowing rearward travel of the slide. The slide rearward motion effects extraction and ejection of the fired cartridge case, and maintains the barrel in a proper recoiled position to receive a fresh cartridge from a pistol magazine. These operations occur as a result of the moment of inertia generated by the mass of the moving projectile or bullet, rather than by the mere gas pressure generated. Examples of these effects are disclosed in U.S. Pat. Nos. 5,433,134 (Leiter), 5,585,589 (Leiter) and 5,675,106 (Leiter). 
         [0007]    In order to provide reliable and repetitive blank-fire in these types of firearms, modifications to the barrel may be provided beyond the presence of a bore-restricting or occluding element that generates back pressure within the bore to produce recoil. These modifications to the barrel remove or modify interference by the breech-lock provision, and compensate for consequent ungoverned and un-timed barrel motion imparted by the slide as the barrel is forced rearward under recoil. An example device for overcoming the breech-lock obstacle that ordinarily hampers blank-fire operation is disclosed in aforementioned U.S. Pat. No. 5,433,134 (Leiter). In addition, rearward displacement of a portion of the rearward underside of the barrel element may be provided to permit free barrel drop into recoil position absent the presence of a timed breech-lock feature, while still allowing engagement of the barrel element by the appropriate frame-abutting element of a pistol receiver. An example of this type of displacement is disclosed in aforementioned U.S. Pat. No. 5,585,589 (Leiter). The Leiter patents discussed above (U.S. Pat. Nos. 5,433,134; 5,585,589; and 5,675,106) are incorporated herein by reference in their entireties. 
         [0008]    However, certain other obstacles may persist within these types of breech-locked firearms that hinder or prevent repetitive blank-fire. These obstacles may arise within pistol designs containing a particular disposition of the battery-indexing element of the frame. An example of this type of obstacle may be present within the H&amp;K USP-series and the H&amp;K P2000-series pistols. The obstacles may further arise within pistols incorporating improvements, altered geometries or dimensional changes in frame design affecting the battery-indexing element, where the alterations often occur for the purpose of strengthening the area surrounding or abutting the battery-indexing provision. An example of this type of obstacle may be present within the Third Generation of GLOCK pistols. 
         [0009]    In the case of each of these obstacles, the design factors impose additional surfaces or material within the frame at the forward portion of the barrel underside critical for blank-fire operation. Further, the frame-mounted projections described above serve to establish a stop point for the barrel and slide when assembled on the frame, and define their locked, in-battery position on the frame. Consequently, a barrel drop into the recoil position is impeded by the presence of forwardly extended frame material (or by a counterpart in another frame-mounted component), and blank-fire cannot be effectively achieved since the barrel cannot clear the impediment that blocks the barrel drop and the continued rearward motion of the slide. Thus, even though the slide no longer contacts the corresponding locking element of the barrel upon discharge (e.g., as disclosed in the aforementioned Leiter patent (U.S. Pat. No. 5,433,134)), it cannot draw the barrel immediately or sufficiently to the rear to bypass the forward areas of the frame that support and hold the barrel in battery position. 
         [0010]    Moreover, regardless of the force the slide imparts to a barrel with breech-lock modification under blank-fire (e.g., refer to the aforementioned Leiter patent (U.S. Pat. No. 5,433,134)), the barrel cannot achieve sufficient velocity to clear the forward frame or frame-mounted element and is re-captured by the reciprocating slide, thereby preventing downward barrel motion through interaction with the rearward frame abutment/support element. This prevents proper timing of barrel motion, drop, and clearance from the reciprocating slide. Since the modified barrel begins motion from a state of rest while the slide has already accelerated under recoil, the barrel cannot gain sufficient velocity to exceed that of the recoiling slide and clear the forward frame abutments beneath the barrel. 
       SUMMARY OF THE INVENTION 
       [0011]    Accordingly, the present invention embodiments provide a barrel component with the forward under-portion of the barrel configured in various manners. For example, the configurations may include an upward displacement, or angular or radial contouring, of barrel material at the forward underside of a barrel component understation or projection. These configurations provide clearance to allow the barrel to bypass frame-mounted impediments to blank-fire, and permit proper timing and coordination of rearward barrel motion under impact of the recoiling slide and the resultant barrel drop into recoil position without interference with, or re-capture by, the reciprocating slide component. 
         [0012]    In addition, blank-fire operation may be enhanced to include laser targeting or laser signature capability. In particular, the blank-fire barrel may be configured to incorporate a threaded laser device. This capability is of particular value in law enforcement and military training usages, and commercial applications, where realistic firearm operation is afforded by blank-fire when laser-marking capability is available to replicate bullet point of impact. This affords both marksmanship training and the ability to conduct realistic tactical training exercises absent the inherent restrictions and dangers attendant with the use of live ammunition. 
         [0013]    The above and still further features and advantages of the present invention will become apparent upon consideration of the following detailed description of example embodiments thereof, particularly when taken in conjunction with the accompanying drawings wherein like reference numerals in the various figures are utilized to designate like components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a side view in perspective of an internal configuration of an example Heckler and Koch type pistol for use with a present invention embodiment. 
           [0015]      FIG. 2  is view in elevation of a conventional barrel unit for the pistol of  FIG. 1 . 
           [0016]      FIG. 3  is a side view in perspective of the internal configuration of the pistol of  FIG. 1  including a blank-fire barrel unit according to an embodiment of the present invention. 
           [0017]      FIG. 4  is a view in elevation of the blank-fire barrel unit of the pistol of  FIG. 3  according to an embodiment of the present invention. 
           [0018]      FIG. 5  is an exploded view in partial section of the blank-fire barrel unit of  FIG. 4  configured to receive a laser device according to an embodiment of the present invention. 
           [0019]      FIG. 6A  is a side view in perspective of an example third generation GLOCK type pistol for use with a present invention embodiment. 
           [0020]      FIG. 6B  is a view in perspective of the frame of the example third generation GLOCK type pistol of  FIG. 6A   
           [0021]      FIG. 7  is a top perspective view of example second and third generation GLOCK type pistols for use with a present invention embodiment. 
           [0022]      FIG. 8  is a view in elevation of a conventional barrel unit for the pistol of  FIGS. 6A-6B . 
           [0023]      FIG. 9  is a close-up view of a portion of the barrel unit of  FIG. 8 . 
           [0024]      FIG. 10  is a view in elevation of a blank-fire barrel unit for the pistol of  FIGS. 6A-6B  according to an embodiment of the present invention. 
           [0025]      FIG. 11  is a close-up view of a portion of the blank-fire barrel unit of  FIG. 10 . 
           [0026]      FIG. 12  is an exploded view in partial section of the blank-fire barrel unit of  FIG. 10  configured to receive a laser device according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    An example Heckler and Koch type pistol  20  for use with present invention embodiments is illustrated in  FIGS. 1-2 . Specifically, firearm or pistol  20  includes a frame  1 , a slide  2  mounted on frame  1 , a barrel unit  3 A, and a recoil spring mechanism  5 . Frame  1  includes a trigger mechanism  18  with a hammer  16 , and a handle or grip portion  19  housing a magazine  21  for storage of one or more cartridges  28 . Slide  2  is mounted on frame  1  and is adapted for reciprocal longitudinal movement on the frame in response to firing of pistol  20 . Barrel unit  3 A includes a chamber portion  41 A and a barrel portion  43 A. The chamber portion underside or bottom surface includes forward understations or projections  9 ,  25  and a rear understation or projection  26 . Projections  9  and  25  adjoin each other with projection  25  basically forming a shoulder (e.g., or non-planar geometry) with the bottom surface of barrel portion  43 A, while rear projection  26  is separated from front projection  9  by a suitably dimensioned gap or recess  45 . The barrel unit is slidable and tillable relative to slide  2 , and is operatively connected to frame  1 . Spring recoil mechanism  5  is positioned below barrel portion  43 A, and returns slide  2  and barrel unit  3 A to the forward battery position after recoil as described below. 
         [0028]    The barrel unit and slide are locked together toward intermediate portions of those components. Pistol  20  typically includes a breech-lock mechanism in the form of a vertical abutment surface  29  of slide  2  engaging a vertical abutment surface  24  disposed on a top surface of chamber portion  41 A. Abutment surface  24  basically forms a shoulder (e.g., or non-planar geometry) with the barrel portion top surface to engage abutment surface  29 . The breech-lock mechanism collectively drives barrel unit  3 A and slide  2  rearwardly to an appropriate position during recoil. Spring recoil mechanism  5  is positioned below barrel portion  43 A and returns slide  2  and barrel unit  3 A to the forward battery position after recoil as described below. 
         [0029]    Normal live-fire indexing and maintenance of slide  2  and barrel unit  3 A in a battery position is accomplished by a combination of recoil spring mechanism  5  and a barrel support  13 . The barrel support includes lower and upper recesses  22 ,  23  respectively defined in barrel support top and bottom surfaces, and is removably affixed to frame  1  by a slide-stop latch pin  17  disposed within barrel support lower recess  22  above trigger  18 . Forward understation or projection  9  of barrel unit  3 A is disposed within upper recess  22  and abutts barrel support  13  to maintain barrel unit  3 A in a locked in-battery position. Further, the combination of barrel unit  3 A and barrel support  13  are fixed in their locked in-battery position by latch pin  17  contacting a rearward portion of barrel support lower recess  22  to prevent forward motion of the assembled elements (e.g., slide  2 , barrel unit  3 A, barrel support  13 , etc.). Rearward motion of the assembled elements is precluded by contact of barrel support  13  with frame  1  adjacent spring recoil mechanism  5 . 
         [0030]    Upon discharge of pistol  20 , barrel unit  3 A and slide  2  (e.g., engaged by abutment surfaces  24  and  29  forming the breech-lock mechanism) move rearward, and rear barrel understation  26  clears barrel support  13 . The barrel unit is further drawn downward by the engagement of projection  9  with barrel support  13  (e.g., projection  9  being disposed within barrel support lower recess  22 ) to provide fired cartridge extraction and ejection, and to be placed in position to receive a fresh cartridge housed within magazine  21  of handle  19 . This interaction of elements is dimensionally timed to enable forward understation or projection  25  to clear barrel support  13  by the moment of barrel drop. Projection  25  basically bypasses a support surface  27  disposed between barrel support upper recess  23  and spring recoil mechanism  5  through the coordinated support of the bottom surface of rear projection  26 , thereby permitting correct and unimpeded separation of the barrel unit from the reciprocating slide (e.g., disengagement of barrel abutment surface  24  from slide abutment surface  29 ). This rearward distance is traversed by barrel unit  3 A to allow proper barrel drop, and for this to occur, immediate barrel unit motion accompanies initial slide motion. 
         [0031]    Pistol  20  including a blank-fire barrel unit of a present invention embodiment is illustrated in  FIGS. 3-4 . Initially, pistol  20  is substantially similar to the pistol described above and includes a blank-fire barrel unit  32 A. The blank-fire barrel unit is similar to barrel unit  3 A described above and includes chamber portion  41 A and barrel portion  43 A. The chamber portion underside or bottom surface includes forward understation or projection  9 , rear understation or projection  26  separated from front projection  9  by suitably dimensioned gap or recess  45 , and an area  30  adjacent forward projection  9 . The chamber portion top surface includes abutment surface  24 . The blank-fire barrel unit includes various modifications to at least abutment surface  24 , rear understation or projection  26  and area  30  as described below to enable and enhance repetitive blank fire. 
         [0032]    Abutment surface  24  of barrel unit  32 A is configured to obviate immediate contact between slide  2  and barrel unit  32 A. In particular, abutment surface  24  includes a rearwardly inclined surface  33  angled in an approximate range of eight to fifteen degrees, and preferably ten to thirteen degrees, relative to a barrel unit longitudinal axis. This diminishes the effect of initial barrel unit/slide locking by enabling a predetermined distance of free travel of slide  2  rearward during recoil, thereby producing a delay between the slide rearward movement and contact with barrel inclined surface  33 . For an example of this type of configuration, reference is made to the aforementioned Leiter patents. 
         [0033]    Rear understation or projection  26  of barrel unit  32 A is configured to allow for correct rear barrel drop. In particular, rear understation or projection  26  is configured with a shorter dimension by moving a forward most upwardly-angled surface  31  of the projection to the rear at an oblique angle, preferably approximating the angle configuration for projection  26  of barrel unit  3 A of  FIG. 1 . This effectively increases the dimensions of gap  45  and shortens the projection contact with the frame, thereby reducing the time and distance necessary for barrel unit  32 A to drop downwardly into the rearward recoil/cartridge feeding position. Consequently, the amount of recoil force required to drive the slide and barrel unit rearwardly is reduced. Preferably, understation or projection  26  is shortened (or gap  45  is lengthened) by approximately 25% to 75% relative to barrel unit  3 A (e.g., includes a reduced length in the approximate range of 0.075 to 0.225 inches). For an example of this type of configuration, reference is made to the aforementioned Leiter patents. 
         [0034]    The combination of angled abutment surface  24  and shortened understation or projection  26  (or lengthened gap  45 ) assists pistol  20  to operate in a repetitive automatic manner with the barrel unit dropping to a cartridge feeding position at the appropriate time sequence. Barrel unit  32 A may further include a restrictor element or occlusion  47  disposed at any suitable location (e.g., proximal or distal end, intermediate portion, etc.) within barrel portion  43 A to generate sufficient back pressure upon firing of a blank cartridge to drive slide  2  and barrel unit  32 A rearwardly, while recoil spring mechanism  5  returns slide  2  and barrel unit  32 A to the battery position as described above. 
         [0035]    Since the immediate contact between slide  2  and barrel unit  32 A has been removed by inclined surface  33  of abutment surface  24  as described above, no manner exists to permit barrel forward understation or projection  25  ( FIG. 1 ) to clear support surface  27 . Accordingly, the removal (or modification) of forward understation or projection  25  is embodied in area  30  ( FIG. 4 ), where forward barrel drop and separation from the reciprocating slide is timed to bypass contact with support surface  27 . By way of example only, area  30  of barrel unit  32 A represents a barrel unit configuration with the removal of understation or projection  25 . In this case, area  30  of chamber portion  41 A is substantially flush (or planar) with the bottom surface of barrel portion  43 A, and extends to a forward or front surface of projection  9 . However, barrel unit  32 A may alternatively include understation or projection  25  configured in any fashion to bypass support surface  27  (e.g., adjustment of any suitable projection dimensions). 
         [0036]    Barrel unit  32 A may further be configured to receive a laser device emitting a laser beam upon firearm actuation. This provides enhanced capabilities with respect to training and marksmanship applications. Referring to  FIG. 5 , barrel unit  32 A is substantially similar to the barrel unit described above for  FIGS. 3-4 , and includes chamber portion  41 A and barrel portion  43 A. The chamber portion receives blank cartridge  28  ( FIG. 3 ) and includes a bore area  49  to provide for expansion of combustion gases. The chamber portion underside or bottom surface includes forward understation or projection  9 , rear understation or projection  26  separated from front projection  9  by suitably dimensioned gap or recess  45 , and area  30  adjacent forward projection  9 , each as described above. The chamber portion top surface includes abutment surface  24  as described above. The barrel portion includes a muzzle  37  disposed at a barrel portion distal end, and a receiving chamber  39  disposed proximally of muzzle  37  to receive a laser device  75  therein. Laser device  75  may be of the type disclosed in U.S. Pat. No. 6,322,365 (Shechter et al.), the disclosure of which is incorporated herein by reference in its entirety. 
         [0037]    Solid occluding element or occlusion  47  is disposed between receiving chamber  39  and bore area  49 . Occlusion  47  prevents passage of a projectile through barrel unit  32 A, and further prevents combustion gases from reaching laser device  75  disposed within muzzle  37 . The combustion gases may damage the laser device and/or propel the laser device from the barrel unit. The laser device housing and internal mechanism are housed within receiving chamber  39 . The laser device housing includes threading  46  disposed about the housing distal end external perimeter, while corresponding threads  36  are disposed about the internal perimeter of muzzle  37 . Laser device  75  is removably affixed to the barrel unit by inserting the laser device into receiving chamber  39  and engaging muzzle threads  36  with laser device housing threads  46 . Receiving chamber  39  includes transverse cross-sectional dimensions (e.g., diameter, etc.) in the approximate range of 0.312 to 0.375 inches, and a depth sufficient to provide occlusion  47  with longitudinal dimensions of approximately 0.100 to 0.750 inches. The particular dimensions of receiving chamber  39  depend upon the size and design of the laser device. The longitudinal depth of muzzle threads  36  is approximately 0.250 to 0.500 inches, and depends upon the laser device geometries and the dimensional geometries of the barrel unit, where the combination of elements allows for the minimum occlusion dimension noted above. Further, muzzle threads  36  include a thread dimension and pitch matching that of laser device housing threads  46 , and are preferably configured to include a thread dimension of approximately 7/16 of an inch with a pitch in the approximate range of 24 to 48 threads per inch. The particular specifications of thread dimensions and pitch are determined by the specific geometry of the laser device and the muzzle dimensions. In any case, muzzle threads  36  are configured to provide positive thread engagement without weakening the surrounding barrel unit material. 
         [0038]    An example third generation GLOCK type pistol  40  for use with present invention embodiments is illustrated in  FIGS. 6A-6B  and  8 - 9 . Specifically, firearm or pistol  40  includes frame  1 , slide  2  mounted on frame  1 , a barrel unit  3 B, and a disassembly latch or slide lock  4 . Frame  1  includes trigger mechanism  18  with a hammer (not shown), and handle or grip portion  19  housing a magazine to store one or more cartridges (not shown). Slide  2  is mounted on frame  1  and is adapted for reciprocal longitudinal movement on the frame in response to firing of pistol  40 . Barrel unit  3 B ( FIGS. 8-9 ) includes a chamber portion  41 B and a barrel portion  43 B. The chamber portion underside or bottom surface includes a forward understation or projection  52  with a bottom surface  12 , and a rear understation or projection  54 . Rear projection  54  is separated from front projection  52  by a suitably dimensioned gap or recess  55 . A front surface  60  of forward projection  52  includes an upper shoulder  62  formed with and disposed below a bottom surface of barrel portion  43 A, a recess  64  defined in surface  60  below shoulder  62  and a lower projection  66 A disposed adjacent recess  64 . Lower projection  66 A includes a front angled surface  14 , and a bottom surface  68  substantially parallel with a barrel unit longitudinal axis. The lower projection bottom surface forms a front portion of bottom surface  12  of front projection  52 . The barrel unit is slidable and tiltable relative to slide  2 , and is operatively connected to frame  1 . A spring recoil mechanism (not shown) returns slide  2  and barrel unit  3 B to the forward battery position after recoil as described below. 
         [0039]    The barrel unit and slide are locked together toward intermediate portions of those components. Pistol  40  typically includes a breech-lock mechanism in the form of a vertical abutment surface  56  of slide  2  ( FIG. 6A ) engaging a vertical abutment surface  11  disposed on a top surface of chamber portion  41 B ( FIGS. 8-9 ). Abutment surface  11  basically forms a shoulder (e.g., or non-planar geometry) with the barrel portion top surface to engage slide abutment surface  56 . The breech-lock mechanism drives slide  2  and barrel unit  3 B rearwardly to an appropriate position during recoil. The spring recoil mechanism (not shown) returns slide  2  and barrel unit  3 B to the forward battery position after recoil as described below. Slide lock  4  further serves as the battery indexing provision that locks the barrel unit and slide in forwardmost firing position. Basically, the slide lock or disassembly latch ( FIGS. 6A and 7 ) engages forward projection  52  ( FIGS. 8-9 ) to position and hold the barrel unit in battery position within frame  1 . 
         [0040]    A comparative top view of second and third generation GLOCK type pistols  35 ,  40  is illustrated in  FIG. 7 . Pistol  35  includes corresponding frame  10 , while pistol  40  includes frame  1  as described above. Third generation pistol frame  1  includes a frame buttress area  15 A that is disposed at a higher location on the surface of slide lock  4  relative to the location of corresponding frame buttress  15  on slide lock  4  of second generation pistol  35 . In addition, frame buttress  15 A of the third generation pistol frame forms a different rearward angle, and contains additional frame material that extends further rearward within the frame  1  relative to second generation frame  10 . 
         [0041]    Upon discharge of pistols  35 ,  40 , barrel unit  3 B and slide  2  (e.g., engaged by abutment surfaces  11  and  56  forming the breech-lock mechanism) move rearward, where prior to barrel drop into recoil position, bottom surface  68  of front projection  52  clears frame buttress  15  and  15 A. However, the extended buttress area of frame  15 A interferes with correct rearward barrel motion, timing, and drop into recoil position and, consequently, interferes with slide travel. 
         [0042]    An embodiment of the present invention provides for proper timing, barrel separation, and barrel drop in blank-fire operation by alteration of the barrel unit as illustrated in  FIGS. 10-11 . Initially, pistol  40  may include a blank-fire barrel unit  32 B ( FIG. 6B ). The blank-fire barrel unit is similar to barrel unit  3 B of pistol  40  described above and includes chamber portion  41 B and barrel portion  43 B. The chamber portion underside or bottom surface includes forward understation or projection  52  with bottom surface  12 , and rear understation or projection  54  separated from front projection  52  by suitably dimensioned gap or recess  55 . Front surface  60  of forward projection  52  includes upper shoulder  62  formed with and disposed below a bottom surface of barrel portion  43 B, recess  64  defined in surface  60  below shoulder  62 , and lower projection  66 B disposed adjacent recess  64 . Lower projection  66 B includes front angled surface  14 , and bottom surface  68  forming a front portion of front projection bottom surface  12 . The chamber portion top surface includes abutment surface  11 . The blank-fire barrel unit includes various modifications to at least abutment surface  11 , front projection  52  and rear projection  54  as described below to enable and enhance repetitive blank fire. 
         [0043]    Abutment surface  11  of barrel unit  32 B is configured to obviate immediate contact between slide  2  and barrel unit  32 B. In particular, abutment surface  11  includes a rearwardly inclined surface  57  angled in an approximate range of eight to forty-five degrees relative to a barrel unit longitudinal axis. This diminishes the effect of initial barrel unit/slide locking by enabling a predetermined distance of free travel of slide  2  rearward during recoil, thereby producing a delay between the slide rearward movement and contact with barrel inclined surface  57 . For an example of this type of configuration, reference is made to the aforementioned Leiter patents. 
         [0044]    Rear understation or projection  54  of barrel unit  32 B is configured to allow for correct rear barrel drop. In particular, rear understation or projection  54  is configured with a shorter dimension by moving a forward most upwardly-angled surface  53  of the projection to the rear at an oblique angle, preferably approximating the forward angle configuration for projection  54  of barrel unit  3 B. This effectively increases the dimensions of gap  55  and shortens the projection contact with the frame, thereby reducing the time and distance necessary for barrel unit  32 B to drop downwardly into the rearward recoil/cartridge feeding position. Consequently, the amount of recoil force required to drive the slide and barrel unit rearwardly is reduced. Preferably, understation or projection  54  is shortened (or gap  55  is lengthened) by approximately 25% to 75% relative to barrel unit  3 B (e.g., includes a reduced length in the approximate range of 0.075 to 0.225 inches). For an example of this type of configuration, reference is made to the aforementioned Leiter patents. 
         [0045]    The combination of angled abutment surface  11  and shortened understation or projection  54  (or lengthened gap  55 ) assists pistol  40  to operate in a repetitive automatic manner with the barrel unit dropping to a cartridge feeding position at the appropriate time sequence. Barrel unit  32 B may further include a restrictor element or occlusion  47  disposed at any suitable location (e.g., proximal or distal end, intermediate portion, etc.) within barrel portion  43 B to generate sufficient back pressure upon firing of a blank cartridge to drive slide  2  and barrel unit  32 B rearwardly, while the recoil spring mechanism returns slide  2  and barrel unit  32 B to the battery position as described above. 
         [0046]    In order to bypass frame buttress impediment  15 A ( FIG. 7 ) to achieve correct timing of barrel drop and separation from the slide for permitting repetitive blank-fire, front surface  14  and/or bottom surface  68  of lower projection  66 B are configured to approximate the angular contour of frame buttress  15 A ( FIG. 7 ). The configurations may include angular and/or radial alterations of front and/or bottom surfaces  14 ,  68  relative to corresponding surfaces of barrel unit  3 B. The particular angular or radial dimensions to be adopted by barrel unit  32 B vary in accordance with specific firearms or pistols employed by the present invention embodiments, and is derived from the specific geometries of the pistol frame. By way of example, the height dimension of front surface  14  may be reduced to bypass frame buttress  15 A (e.g., configure bottom surface  68  to project distally (or proximally) toward (or away from) chamber portion  41 B). For example, front surface  14  of lower projection  66 B may be configured (e.g., with a reduced height or thickness) to provide bottom surface  68  of lower projection  66 B with an angled surface  70  disposed in an angular relation of approximately nine degrees relative to a longitudinal axis or centerline of the barrel unit. The angular relation may further be in the approximate range of one to fifteen degrees. The angle of angled surface  70  relative to the barrel unit longitudinal axis depends upon the nature and power of the blank ammunition employed, and the resultant velocity imparted to slide  2  of the pistol, since the velocity dictates the rapidity with which the barrel unit clears frame buttress impediment  15 A ( FIG. 7 ). 
         [0047]    Alternatively, bottom surface  68  of lower projection  66 B may include a curved configuration (or radial disposition). In particular, bottom surface  68  may include curved surface  72 , preferably arcing outward from (e.g., convex configuration) chamber portion  41 B and diminishing the thickness of surface  14 . Curved surface  72  extends from the lower portion of front surface  14  (e.g., with minimal or no protrusion relative to bottom surface  68  of  FIGS. 8-9 ) for an approximate length of approximately 0.200 to 1.600 inches. However, the length may vary depending upon the desired height or thickness of front surface  14 . Curved surface  72  provides arcuate or curved relief to enable barrel unit  32 B to bypass frame buttress  15 A ( FIG. 7 ). 
         [0048]    Barrel unit  32 B may further be configured to receive a laser device emitting a laser beam upon firearm actuation. This provides enhanced capabilities with respect to training and marksmanship applications. Referring to  FIG. 12 , barrel unit  32 B is substantially similar to the barrel unit described above for  FIGS. 10-11 , and includes chamber portion  41 B and barrel portion  43 B. The chamber portion receives a blank cartridge and includes a bore area  58  to provide for expansion of combustion gases. The chamber portion underside or bottom surface includes forward understation or projection  52 , and rear understation or projection  54  separated from front projection  52  by suitably dimensioned gap or recess  55 , each as described above. The chamber portion top surface includes abutment surface  11  as described above. Barrel portion  43 B includes muzzle  37  disposed at a barrel portion distal end, and a receiving chamber  50  disposed proximally of muzzle  37  to receive laser device  75  therein. Laser device  75  may be of the type disclosed in U.S. Pat. No. 6,322,365 (Shechter et al.) as described above. 
         [0049]    Solid occluding element or occlusion  47  is disposed between receiving chamber  50  and bore area  58 . Occlusion  47  prevents passage of a projectile through barrel unit  32 B, and further prevents combustion gases from reaching laser device  75  disposed within muzzle  37 . The combustion gases may damage the laser device and/or propel the laser device from the barrel unit. The laser device housing and internal mechanism are housed within receiving chamber  50 . The laser device housing includes threading  46  disposed about the housing distal end external perimeter, while corresponding threads  36  are disposed about the internal perimeter of muzzle  37 . Laser device  75  is removably affixed to the barrel unit by inserting the laser device into receiving chamber  50  and engaging muzzle threads  36  with laser device housing threads  46 . Receiving chamber  50  includes transverse cross-sectional dimensions (e.g., diameter, etc.) in the approximate range of 0.312 to 0.375 inches, and a depth sufficient to provide occlusion  47  with longitudinal dimensions of approximately 0.100 to 0.750 inches. The particular dimensions of receiving chamber  50  depend upon the size and design of the laser device. The longitudinal depth of muzzle threads  36  is approximately 0.250 to 0.500 inches and depends upon the laser device geometries and the dimensional geometries of the barrel unit, where the combination of elements allows for the minimum occlusion dimension noted above. Further, muzzle threads  36  include a thread dimension and pitch matching that of laser device housing threads  46 , and is preferably configured to include a thread dimension of approximately 7/16 of an inch with a pitch in the approximate range of 24 to 48 threads per inch. The particular specifications of thread dimensions and pitch are determined by the specific geometry of the laser device and the muzzle dimensions. In any case, muzzle threads  36  are configured to provide positive thread engagement without weakening the surrounding barrel unit material. 
         [0050]    The operative principle of the present invention embodiments may be applied to any types or brands of firearms. The present invention embodiments provide a manner to enable proper timing of barrel/slide separation and barrel drop to permit reliable and repetitive blank-fire operation in various types and designs of breech-locked semiautomatic pistols. 
         [0051]    It will be appreciated that the embodiments described above and illustrated in the drawings represent only a few of the many ways of implementing blank-firing barrels for semiautomatic pistols and method of repetitive blank fire. 
         [0052]    The barrel units may be of any shape or size, and may be configured for any type or brand of firearm (e.g., semiautomatic pistol, hand-gun, etc.). The chamber and barrel portions may be of any size or shape, and occupy any desired portions of the barrel units. The abutment surfaces of the barrel units may be of any quantity, shape or size, and may be disposed at any suitable locations to engage the slide. The occlusion may be of any quantity, shape or size, may be constructed of any suitable materials, and may be disposed at any suitable locations (e.g., proximal end, distal end, intermediate portions, etc.) within the chamber and/or barrel portions of the barrel units. 
         [0053]    The inclined surfaces of the barrel unit abutment surfaces may be oriented at any desired angles or angle ranges (e.g., preferably acute angles in the approximate range of one to ninety degrees, etc.) in any desired directions (e.g., rearward, etc.). The forward and rear understations or projections of the chamber portions may be of any quantity, shape or size and may be disposed at any suitable locations and/or arranged in any desired fashion. The gap between the forward and rear understations or projections may be of any desired dimensions and/or the dimensions of the rear understation or projection may be configured in any manner to bypass frame obstacles for suitable barrel drop. 
         [0054]    Forward projection  25  of barrel unit  32 A may be modified in any fashion to bypass support surface  27  or other obstacles of a firearm or frame. For example, the forward projection may be removed from the barrel unit. Further, projection  25  may include reduced dimensions or a modified configuration (e.g., curved, contoured, tapered, etc.) to bypass the support surface or other obstacle. 
         [0055]    Forward projection  52  may be of any shape or size. The upper shoulder, recess and lower projection may be of any quantity, shape or size and disposed at any suitable locations. Lower projection  66 B of barrel unit  32 B may be modified in any fashion to bypass the frame buttress or other obstacles of a firearm or frame. For example, the height or thickness dimensions of front surface  14  may be adjusted in any fashion. Further, the surfaces of lower projection  66 B may include any configurations (e.g., curved or arcuate toward any direction, contoured, tapered, tilted at any desired angles (e.g., preferably acute angles in the range of one to ninety degrees), scalloped or sinusoidal, substantially or entirely removed, etc.) to bypass the frame buttress or other obstacles. The various configurations may include any suitable dimensions or dimension ranges. 
         [0056]    Moreover, the upper shoulder and recess may be modified in substantially the same manner as the lower projection. By way of example, the dimensions of one or more of these elements may be adjusted in any fashion. In addition, these elements may include various configurations (e.g., curved, contoured, tapered, tilted at any desired angles (e.g., preferably acute angles in the range of one to ninety degrees), scalloped or sinusoidal, substantially or entirely removed, etc.) to bypass obstacles for blank fire. 
         [0057]    The threads of the barrel units may be of any quantity, shape or size, may include any desired dimensions, spacing or pitch, and may be disposed at any suitable locations (e.g., proximal end, distal end, intermediate portions, etc.) on or within the chamber and/or barrel portions of the barrel units to engage the laser device. The threads of the laser device may be of any quantity, shape or size, may include any desired dimensions, spacing or pitch, and may be disposed at any suitable locations on or within the housing (e.g., proximal end, distal end, intermediate portions, etc.). The laser device may be implemented by any conventional or other laser device to project a laser beam or other energy form (e.g., light, infrared, sound, etc.) from the barrel units in response to any conditions (e.g., trigger or firearm actuation, etc.). The laser device may be permanently or removably affixed to the barrel unit interior or exterior by any conventional or other securing techniques (e.g., fasteners, threaded engagement, friction fit, etc.). The receiving chambers may be of any quantity, shape or size to receive any portions of the laser device (e.g., the laser device may be partially or entirely disposed within the barrel units). 
         [0058]    The barrel units of the present invention embodiments may be utilized in combination with any suitable type or brand of firearms to produce a firearm with repetitive blank fire capability. Further, the various configurations of the barrel unit elements (e.g., abutment surface, forward and rear projections, etc.) may be utilized by a barrel unit either individually, or in any desired combinations, to enable repetitive blank fire. 
         [0059]    It is to be understood that the terms “top”, “bottom”, “front”, “rear”, “side”, “height”, “length”, “width”, “upper”, “lower”, “forward” and the like are used herein merely to describe points of reference and do not limit the present invention embodiments to any particular orientation or configuration. 
         [0060]    The barrel units are not limited to the applications or firearms described above, but may be utilized to facilitate repetitive blank-fire in any types or brands of firearms. 
         [0061]    From the foregoing description, it will be appreciated that the invention makes available novel blank-firing barrels for semiautomatic pistols and method of repetitive blank fire, wherein a forward under-portion of a barrel is configured in various manners to provide clearance to allow the barrel to bypass frame-mounted impediments to blank-fire. 
         [0062]    Having described preferred embodiments of new and improved blank-firing barrels for semiautomatic pistols and method of repetitive blank fire, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the teachings set forth herein. It is therefore to be understood that all such variations, modifications and changes are believed to fall within the scope of the present invention as defined by the appended claims.