Abstract:
A system for removably securing a hand guard to a semi-automatic or automatic rifle is provided. The system having: a first locking assembly for removably coupling a rear end of the hand guard to an upper receiver of the rifle; a second locking assembly for removably coupling a forward end of the hand guard to the rifle; and wherein the first locking assembly and the second locking assembly axially and rotationally position the hand guard with respect to the rifle and wherein the hand guard is not directly secured to a barrel of the rifle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 11/869,676 filed Oct. 9, 2007, which claims the benefit of U.S. Application No. 60/849,957, filed Oct. 6, 2006, the contents each of which are incorporated herein by reference thereto. 
     
    
     FIELD 
       [0002]    The disclosed embodiments relate to firearms and, more particularly, to a firearm having a removable hand guard. 
       BACKGROUND 
       [0003]    There is a demand from operators that firearms, such as automatic and semi-automatic rifles, have increased versatility allowing use of the firearm in different conditions. For example, operation desire to mount and switch between different accessory or peripheral devices to automatic and semi-automatic rifles that aid operator use of the firearm on different conditions. In addition to heightened versatility, operators desire robust construction and ease of operability and maintenance allowing the firearm to be versatile while being easy to use and having minimum maintenance needs even when undergoing harsh use in harsh conditions such as high humidity or high dust. Conventional firearms have not successfully satisfied the demands and desires of operators. U.S. Pat. No. 5,824,943 dated Oct. 20, 1998, discloses an example of a conventional self loading rifle with a gas pressure loading arrangement. The conventional gas pressure loading arrangement disclosed includes a gas cylinder fluidly connected to the bore of the rifle barrel, and a gas piston received in the gas cylinder to define a gas chamber. The gas chamber is readily susceptible to fowling resulting in stoppage of the firearm. The exemplary embodiments of the firearms disclosed herein overcome the problems of conventional firearms as will be further described below. 
       SUMMARY OF THE INVENTION 
       [0004]    In accordance with one exemplary embodiment, a semi-automatic or automatic rifle is provided. The rifle has a receiver having a receiver frame, a barrel removably connected to the receiver frame and a cover coupled to the barrel. A removable hand guard section extends over and generally surrounds the barrel, the hand guard has at least two removable hand guard section pieces removably and independently connected to the receiver. The removable hand guard pieces has a locating feature adapted to engage with the cover and locate the at least two pieces relative to the cover. The locking collar mounted to the barrel and is adapted to removably position and lock the at least two pieces relative to the receiver frame and the barrel. The at least two pieces float in position relative to the barrel. 
         [0005]    In accordance with another exemplary embodiment, a semi-automatic or automatic rifle is provided. The rifle has a receiver having a receiver frame, a barrel removably connected to the receiver frame and a cover coupled to the barrel. A two piece removable hand guard section extends over and generally surrounds the barrel, the two piece removable hand guard section removably connected to the receiver. The two piece removable hand guard section has locating features adapted to engage with the cover and locate the two piece hand guard relative to the cover. The barrel has a locking collar adapted to removably position and lock the two piece removable hand guard section relative to the receiver frame and the barrel. The two piece removable hand guard floats in position relative to the barrel. 
         [0006]    In accordance with another exemplary embodiment, a semi-automatic or automatic rifle is provided. The rifle has a receiver having a receiver frame and a barrel connected to the receiver frame. An indirect gas operating system has a gas block and a movable piston, the gas block coupled to the barrel, the gas block in fluid communication with the barrel, the movable piston in communication with the gas block. A cover is coupled to the barrel with a removable hand guard section extending over and generally surrounds the barrel, the removable hand guard section removably connected to the receiver. The removable hand guard section has a locating feature adapted to engage with the cover and locate the hand guard relative to the cover. A locking feature is adapted to removably position and lock the removable hand guard section relative to the receiver frame and the barrel. The removable hand guard floats in position relative to the barrel. 
         [0007]    In accordance with another exemplary embodiment, a semi-automatic or automatic rifle is provided. The rifle has a receiver having a receiver frame and a barrel connected to the receiver frame. An indirect gas operating system has a gas block and a movable piston, the gas block coupled to the barrel, the gas block in fluid communication with the barrel, the piston in communication with a cylinder within the gas block. The cylinder and the piston are removable from a front of the firearm without disassembly of the firearm. A cover is coupled to the barrel. A removable hand guard section extends over and generally surrounds the barrel, the removable hand guard section removably connected to the receiver. The removable hand guard section has a locating feature adapted to engage with the cover and locate the hand guard relative to the cover. A locking feature is adapted to removably position and lock the removable hand guard section relative to the receiver frame and the barrel. The removable hand guard floats in position relative to the barrel. 
         [0008]    In accordance with another exemplary embodiment, a semi-automatic or automatic rifle is provided. The rifle has a receiver having a receiver frame and a barrel connected to the receiver frame. An indirect gas operating system has a gas block and a movable piston, the gas block coupled to the barrel, the gas block in fluid communication with the barrel, the piston in communication with a cylinder within the gas block. The cylinder and the piston removable from a front of the firearm without disassembly of the firearm. The cylinder has an exhaust port on a side of the cylinder in fluid communication with a port in a side wall of the gas block. Exhaust gas is expelled from a side wall of the gas block and offset from a sight line of the firearm. 
         [0009]    In accordance with another exemplary embodiment, a system for removably securing a hand guard to a semi-automatic or automatic rifle is provided. The system having: a first locking assembly for removably coupling a rear end of the hand guard to an upper receiver of the rifle; a second locking assembly for removably coupling a forward end of the hand guard to the rifle; and wherein the first locking assembly and the second locking assembly axially and rotationally position the hand guard with respect to the rifle and wherein the hand guard is not directly secured to a barrel of the rifle. 
         [0010]    In another exemplary embodiment, a semi-automatic or automatic rifle is provided. The rifle having: a system for removably securing a hand guard to the rifle, the system comprising: a first locking assembly for removably coupling a rear end of the hand guard to an upper receiver of the rifle; a second locking assembly for removably coupling a forward end of the hand guard to the rifle; and wherein the first locking assembly and the second locking assembly axially and rotationally position the hand guard with respect to the rifle and wherein the hand guard section is not directly secured to a barrel of the rifle. 
         [0011]    In yet another embodiment, a method for removably securing a hand guard to a semi-automatic or automatic rifle is provided. The method including the steps of: removably coupling a rear end of the hand guard to an upper receiver of the rifle with a first locking assembly; removably coupling a forward end of the hand guard to the rifle with a second locking assembly; and wherein the first locking assembly and the second locking assembly axially and rotationally position the hand guard with respect to the rifle and wherein the hand guard is not directly secured to a barrel of the rifle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The foregoing aspects and other features of the exemplary embodiments are explained in the following description, taken in connection with the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a side elevation view of an automatic firearm incorporating features in accordance with an exemplary embodiment; 
           [0014]      FIG. 2  is an exploded isometric view of the automatic firearm shown in  FIG. 1 ; 
           [0015]      FIG. 3A  is an isometric view of the front sight section of the firearm shown in  FIG. 1 ; 
           [0016]      FIG. 3B  is a partial section view of the front sight shown in  FIG. 3A ; 
           [0017]      FIG. 3C  is a front view of the front sight shown in  FIG. 3A ; 
           [0018]      FIG. 3D  is a bottom view of the front sight shown in  FIG. 3A ; 
           [0019]      FIG. 3E  is a section view of the front sight shown in  FIG. 3A ; 
           [0020]      FIG. 3F  is a partial section view of the front sight shown in  FIG. 3A ; 
           [0021]      FIG. 3G  is a partial section view of the front sight shown in  FIG. 3A ; 
           [0022]      FIG. 4  is a partial side elevation view of the automatic firearm shown in  FIG. 1  having an alternate embodiment sight; 
           [0023]      FIG. 5A  is a partial section side view of the alternate embodiment sight shown in  FIG. 4 ; 
           [0024]      FIG. 5B  is a partial section front view of the alternate embodiment sight shown in  FIG. 4 ; 
           [0025]      FIG. 6  is an elevation view of a barrel assembly of the automatic firearm shown in  FIG. 1 ; 
           [0026]      FIG. 7  is a partial section view of the barrel assembly shown in 
           [0027]      FIG. 6 ; 
           [0028]      FIG. 8A  is a front view of a barrel nut; 
           [0029]      FIG. 8B  is a section view of a barrel nut; 
           [0030]      FIG. 9A  is a front view of a barrel nut collar; 
           [0031]      FIG. 9B  is a section view of a barrel nut collar; 
           [0032]      FIG. 10A  is an elevation view of an upper receiver; 
           [0033]      FIG. 10B  is a front view of an upper receiver; 
           [0034]      FIG. 10C  is a partial section view of an upper receiver; 
           [0035]      FIG. 11A  is a bottom view of an upper hand guard; 
           [0036]      FIG. 11B  is a side view of an upper hand guard; 
           [0037]      FIG. 11C  is a top view of an upper hand guard; 
           [0038]      FIG. 11D  is an end view of an upper hand guard; 
           [0039]      FIG. 12A  is a side view of a lower hand guard; 
           [0040]      FIG. 12B  is a top view of a lower hand guard; 
           [0041]      FIG. 12C  is an end view of a lower hand guard; 
           [0042]      FIG. 13A  is an end view of an end cap; 
           [0043]      FIG. 13B  is a section view of an end cap; 
           [0044]      FIG. 14A  is an end view of an alternate embodiment sight; 
           [0045]      FIG. 14B  is a side view of the alternate embodiment sight; 
           [0046]      FIG. 14C  is an isometric view of the alternate embodiment sight; 
           [0047]      FIG. 14D  is an isometric view of the alternate embodiment sight with the cylinder removed; 
           [0048]      FIG. 15  is an isometric view of a gas block in accordance with an exemplary embodiment; 
           [0049]      FIG. 16A  is a front view, partially in section of the alternate embodiment sight with the cylinder removed; 
           [0050]      FIG. 16B  is a side view, partially in section of the alternate embodiment sight with the cylinder removed; 
           [0051]      FIG. 16C  is a rear view, partially in section of the alternate embodiment sight with the cylinder removed; 
           [0052]      FIG. 17A  is a side view of a gas block in accordance with another exemplary embodiment; 
           [0053]      FIG. 17B  is a partial section view of the gas block; 
           [0054]      FIG. 17C  is a partial section view of the gas block; 
           [0055]      FIG. 17D  is a partial view of the gas block; 
           [0056]      FIG. 17E  is a partial section view of the gas block; 
           [0057]      FIG. 18  is an isometric view of a take down pin; 
           [0058]      FIG. 19  is an isometric view of a gas cylinder; 
           [0059]      FIG. 20A  is a top view of the gas cylinder; and 
           [0060]      FIG. 20B  is a section view of the gas cylinder. 
       
    
    
     DETAILED DESCRIPTION 
       [0061]    Referring to  FIG. 1 , there is shown, a side elevation view of an automatic firearm  20  capable of automatic or semiautomatic fire incorporating features in accordance with an exemplary embodiment. Although the present invention will be described with reference to the embodiments shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms of embodiments. In addition, any suitable size, shape or type of elements or materials could be used. 
         [0062]    Firearm  20  is illustrated as generally having what is known generally as a “black rifle” configuration. The black rifle configuration being the family of rifles developed by Eugene Stoner, for example, such as an M4™ (available from Colt Defense, LLC) or M16 type automatic firearm configuration. However, the features of the disclosed embodiments, as will be described below, are equally applicable to any desired type of automatic firearm. Firearm  20  may have operational features such as disclosed in U.S. Pat. Nos. 5,726,377, 5,760,328, 4,658,702 and 4,433,610, and patent application Ser. Nos. 60/564,895; 10/836,443 filed respectively on Apr. 23, 2004 and Apr. 30, 2004, all of which are hereby incorporated by reference herein in their entirety. The firearm  20  and its sections described in greater detail below is merely exemplary, and in alternate embodiments the firearm  20  may have other sections, portions or systems. For example the firearm  20  may also include one or more features described and shown in U.S. Application No. 60/772,494, filed Feb. 9, 2006, (Attorney Docket No.: 879P012453-US(-#1); and/or, U.S. application Ser. No. 11/231,063, filed Sep. 19, 2005, (Attorney Docket No. 879P011966-US(PAR); and/or U.S. application Ser. No. 11/339,187, filed Jan. 25, 2006, (Attorney Docket No. 879P012072-US(PAR), and/or U.S. application Ser. No. 11/352,036, filed Feb. 9, 2006, (Attorney Docket No. 879P011843-US(101) all of which are hereby incorporated by reference in their entirety. 
         [0063]    In the exemplary embodiment, firearm  20  may incorporate a removable hand guard  30  having upper hand guard  44  and lower hand guard  46 , a receiver section  32  having upper receiver  36  and lower receiver  38 , a barrel  14 , stock  34 , rear sight  40  and front sight  42 . Hand guard  30  may further incorporate vent holes, ribbing, heat shields or double heat shields and liners to facilitate cooling of the barrel  14  while keeping hand guard  30  at a temperature sufficient for an operator to hold the hand guard. In the embodiment shown, hand guards  44 ,  46  are shown as removable hand guards mounted to the barrel assembly  14  where the top rail on the hand guard  44  is aligned with the upper receiver rail (see  FIGS. 1 and 4 ). Although hand guards  44 ,  46  may be made from any suitable material, such as metal, it should be noted that any suitable material such as plastic, composites or any suitable combination of materials may be provided. Hand guard  30  may have features such as disclosed in U.S. Pat. Nos. 4,663,875 and 4,536,982, both of which are hereby incorporated by reference herein in their entirety. In the exemplary embodiment, hand guard  30  may have an aluminum shell and having vent holes and external ribbing. Hand guard  30  may be ergonomically sized to allow a user to comfortably grip the guard. In alternate embodiments, multiple shells, inner ribbing, heat shields or double heat shields and liners to facilitate cooling of the barrel  14  while keeping hand guard  30  at a temperature sufficiently low for an operator could be provided. In alternate embodiments, removable and relocatable rails may be provided on hand guard  30  and may be permanently mounted or removably mounted and be removable or moveable to different locations on hand guard  30 . The rails and mounting system to the hand guard may be substantially similar to rails described in U.S. patent application Ser. No. 11/113,525 filed Apr. 25, 2005, which is incorporated by reference herein in its entirety. In alternate embodiments, rails may be in different locations with different sizes. Hand guard  30  and receiver section  32  may be configured to support such rails as a “Piccatiny Rail” configuration as described in Military Standard 1913, which is hereby incorporated by reference herein in its entirety. The rails may be made from any suitable material such as hard coat anodized aluminum as an example. In the exemplary embodiment, front sight assembly  42  is shown mounted to barrel  14  (see  FIG. 1 ). In alternate embodiments, front sight assembly  42  may be removable, allowing alternate mounting of desired accessory in its place such as a telescopic sight or laser sight. Rear sight assembly  40  is provided and mounted to receiver section  32 . Rear sight assembly  40  may incorporate a sight ring and sight adjustment knobs provided to adjust the position of sight ring relative to the barrel  14  and front sight  42  for accurate target sighting. 
         [0064]    Referring now to  FIG. 2 , there is shown an exploded isometric view of the automatic firearm  20  shown in  FIG. 1 . As noted before the modular auto or semiautomatic rifle  30  may incorporate any one or more of the many features in U.S. Application No. 60/772,494, filed Feb. 9, 2006, U.S. application Ser. No. 11/231,063, filed Sep. 19, 2005, U.S. application Ser. No. 11/339,187, filed Jan. 25, 2006 U.S. application Ser. No. 11/352,036, filed Feb. 9, 2006, U.S. Application No. 60/610,703, filed Sep. 17, 2004, U.S. application Ser. No. 11/672,189, filed Feb. 7, 2007, U.S. application Ser. No. 11/154,738, filed Jun. 16, 2005, and U.S. Application No. 60/646,875, filed Jan. 25, 2005, all of which are hereby incorporated by reference in their entirety. For example, the firearm  20  may incorporate a gas piston system  50  generally similar to embodiments in U.S. application Ser. No. 11/231,063 filed Sep. 19, 2005 previously incorporated by reference in its entirety. As a further example, the rifle may include a rear regulator  52 , for example as shown U.S. application Ser. No. 11/339,187 also previously incorporated by reference in its entirety. The firearm may be provided with “over the beach” capability allowing immediate firing of the weapon after water submersion regardless of weapon orientation. In alternate embodiments, a folding stock may be provided increasing weapon versatility by reducing the overall length to shoulder width. A folding stock further may enhance weapon balance for stability and to retain a target during firing. Greaseless fire control system parts  54  may be provided. For example, the fire control system parts may be coated with a coating, such as UCTD UltraCem R coating to eliminate the need for lubrication and to reduce the accumulation of foreign material and residue and to provide ease in cleaning. As may be realized, the gas piston system operates to effect automatic loading of rounds into the firing chamber of the barrier  14 . The gas piston system  50  may generally include a gas cylinder  506  (described in greater detail below, and a piston  50 P that is connected to a spring loaded operating rod system (e.g. including rod  500 , spring  505  and spring stop  50 T). Removal of the gas piston system  50  may be facilitated in the exemplary embodiment by the removable hand guards  30  as will be described below. In other exemplary embodiments, gas piston system removal may be effected through the front without removal of the hand guards or in the event upper receiver is of unitary construction with an integral hand guard, as will also be described below. 
         [0065]    Referring still to  FIG. 2 , in the embodiment shown, forward extending hand guard/rail system  30  is provided. Hand guard is shown removable yet may be functionally comparable to and with similar alignment features as a one-piece upper receiver extended rail system due to the stabilization design approach (a suitable example of a one-piece upper receiver with integral hand guard section is shown in U.S. application Ser. No. 11/352,036 previously incorporated by reference in its entirety). In the embodiment shown, the rail system/hand guard  30  provides independent movement from the upper receiver and floats with the barrel  14  to increase accuracy and optimizes axis rail mounting options for accessory tailoring and operator handling comfort. The guard is shown as a split guard having upper  36  and lower  38  sections that may be removable. Heat shields may be provided similar to (for example shield described in U.S. application Ser. No. 11/352,036, previously incorporated by reference in its entirety). The heat removal bleeding system protects the operator from barrel heat, increases sustained rate of fire and extends the barrel life. The upper hand guard is shown unitary with integral upper rail  62  (see also  FIGS. 11A-11D ). The upper rail interfaces with and is integrated with the upper receiver  36  upper rail  64  when upper hand guard  44  is mounted. Cap or cover  66  (see also  FIGS. 13A-13B ) is provided on barrel  14  and interfaces with the front  68 ,  70  of the removable hand guard sections  44 ,  46 . In the exemplary embodiment the guards  44 ,  46  and the cap  66  may have complementing conical tapered radially locating features  68 ,  70  that locate and fix the hand guards, eliminating play in the guard mount. In alternate embodiments, the guard mounting to the cap and barrel could have any other radially locating and/or fixing features engaged by longitudinal displacement of the guard. In the exemplary embodiment the upper  44  and lower  46  guards and cap  66  having interlocking facets, for example, in the embodiment shown, a pin  72 ,  74  and hole  76 ,  78  system for rotational positioning. In alternate embodiments, other surfaces, for example, conical surfaces may be provided for radial fixing and/or may be added to pins and holes to simultaneously locate and lock the hand guards in position both in axial, radial and rotational directions. 
         [0066]    The rear portions  80 ,  82  of the hand guards are removably attached to the receiver  36 . In the embodiment shown, attachment of the upper  44  and lower  46  hand guards to the receiver  36  utilizes a tapered radial interlocking rabbett fit between a barrel nut collar  86  and a V-groove  88 ,  90  at the rear  80 ,  82  of the guards  44 ,  46 . Here, the v-groove  88 ,  90  at the rear of the guard interfaces with the barrel nut assembly to removably lock the guards in place. The barrel nut assembly has a barrel nut  92  (see also  FIGS. 8A-8B ) and an outer collar (see also  FIGS. 9A-9B ) threaded onto the barrel nut. Here, the barrel nut has external threads  94  that mate with corresponding thread  96  of the collar  86  for threading the outer collar. In order to engage the guards  44 ,  46 , the outer collar  86  is threaded forwards to engage guards  44 ,  46 . Referring now also to  FIGS. 10A-10C , in the exemplary embodiment the upper receiver  36  may be provided with a manual lock actuator  100  to lock the collar  86  in place after rotation of the collar  86 . In the embodiment shown, the manual lock  100  comprises a spring loaded pin  102 , biased forwards that engages the collar  86 . Here, a thumb pad or any other suitable manual grip may be provided to pull actuator/spring loaded pin  102  back (in the direction indicated by arrow B in  FIG. 10A ), to an open position. The actuator  100  may be locked into the open position against the spring bias, by a second spring loaded detent (as will be described further below). In the embodiment shown a roll pin engaging detent  166  is provided. In alternate embodiments, other suitable actuator, locking device or detent could be provided. The spring loaded pin  102 , in the closed position, engages a saw tooth feature  104  (see  FIG. 9B ) on the collar  86  to prevent rotation of the collar  86  after locking the hand guards  44 ,  46  in position. Removal of the hand guards  44 ,  46  may be effected for example by pulling the thumb pad back (to the open position), rotating the collar  86  away from the guards  44 ,  46 , thus disengaging the v-groove portions  88 ,  90  of the guards  44 ,  46 . In the embodiment shown, the hand guard  44 ,  46  floats with the barrel  14  with the upper rail  62  of the upper hand guard  44  substantially continuous with receiver rail  64 . A rear tab  110  on the hand guard upper rail engages a mating slot  112  on upper receiver rail similar to U.S. application Ser. No. 11/231,063. 
         [0067]    In the embodiment shown, a gas block  42  of unitary construction with an integral sight may be provided. Providing a fixed or folding sight as shown enables an operator&#39;s natural eye capability to align two radial objects for more rapid target acquisition and firing accuracy. In either embodiment, provisions may be made for mounting and removal of the gas piston system  50 , including the removable operating rod and piston assembly from a front of the sight block (e.g. to allow removal without dismounting the hand guards). In either embodiment, a gas exhaust slot &amp; groove with an exhaust port may be provided as will be described in greater detail below. In the exemplary embodiment, the slot extending along an outer side surface of the block and may reduce the possibility of dirt clogging exhaust port as will also be described further below. In alternate embodiments, the exhaust port may be located anywhere and hidden in an exhaust channel so that the port is not directly exposed to dirt. The exhaust channel may have an extended outlet opening so that gas may exhaust through any part of channel that is not blocked. The gas piston system directs gas bleed off to the front of the weapon, decreasing barrel heat and reducing carbon and powder residue accumulation for cleaner functioning. Additionally, the gas piston system reduces gas signature visibility and removes easily in the field for cleaning A bayonet mount lug BMT see  FIGS. 17D-17E  may be provided as a portion of the block or otherwise. 
         [0068]    Referring now to  FIG. 3A  there is shown an isometric view of the front sight section of the firearm  20  shown in  FIGS. 1-2 . Referring also to  FIG. 3B , there is shown a partial section view of the front sight shown in  FIG. 3A . Referring also to  FIG. 3C , there is shown a front view of the front sight shown in  FIG. 3A . Referring also to  FIG. 3D , there is shown a bottom view of the front sight shown in  FIG. 3A . Referring also to  FIG. 3E , there is shown a section view of the front sight shown in  FIG. 3A , referring also to  FIG. 3F , there is shown a partial section view of the front sight shown in  FIG. 3A . Referring also to  FIG. 3G , there is shown a partial section view of the front sight shown in  FIG. 3A . Front sight assembly  42  generally comprises base section  130 , front sight post  132  and a spring loaded pivot or detent assembly  134  spring loaded by spring  136 . In the exemplary embodiment shown in  FIGS. 3A-3E , front sight  42  may comprise a gas block having an integral sight, for example such as disclosed in U.S. application Ser. No. 11/352,036 and/or U.S. Application No. 60/772,494 and/or U.S. application Ser. No. 11/231,063 all of which were previously incorporated by reference herein in their entirety. In the exemplary embodiment shown in  FIGS. 3A-3D , the front sight post  132  has a rounded rim or edge feature  138  that is shaped to substantially coincide with the edges of the hole or ring in rear sight  30  upon alignment of front and rear sights making it easier for a user to acquire targets and center the weapon with the combination. In the exemplary embodiment shown in  FIGS. 3A-3D , the front sight  42  is shown as a fixed sight, wherein the gas block  42  may be of unitary construction with the sight integral thereto, and where material may be removed in recessed section  140  for weight reduction. The arrangement of the sight post on the gas block is representative, and in alternate embodiments the gas block and sight post may have any suitable arrangement. As seen best in  FIG. 3E , in the exemplary embodiment, the base portion  130  of the gas block may define the gas cylinder portion  50 C (see  FIG. 2 ) of the gas piston system  50 . Base  130  may have a closed cylinder  152  (closed at the front end, and forming a piston opening at the back end for piston  50 P. As seen best in  FIG. 3G , a gas exhaust aperture or slot  142  may be formed in a cylinder side, and groove  144  with an exhaust port  146  may be provided. In the exemplary embodiment shown, the exhaust port  146  may have a forward facing opening  148  (see  FIG. 3C . The opening is offset from the front end of the gas cylinder and from the bore sight line of the firearms. The exhaust port opening may be hidden in a slotted channel  148 S. Here, a slot  148 S extending along the outside of block  130  is provided reduces the possibility of dirt clogging exhaust port opening  148 . In alternate embodiments, the exhaust port may be located anywhere, for example, hidden in an exhaust channel so that the port is not directly exposed to dirt. The exhaust channel may have an extended outlet opening so that gas may exhaust through any part of channel that is not blocked. As may be realized, in the exemplary embodiment, the gas piston system directs gas bleed off through port  150  to cylinder  152  through side slot  142  to port  148  directed to the front of the weapon. 
         [0069]    Referring now to  FIG. 4 , there is shown a partial side elevation view of the automatic firearm shown in  FIG. 1  having sight  60  in accordance with another exemplary embodiment. Referring also to  FIG. 5A , there is shown a partial section side view of the alternate embodiment sight  60  shown in  FIG. 4 . Referring also to  FIG. 5B , there is shown a partial section front view of the alternate embodiment sight  60  shown in  FIG. 4 . In the embodiment shown, gas block  60  may have an integral folding sight, for example such as disclosed in U.S. application Ser. No. 11/352,036 and/or U.S. Application No. 60/772,494 and/or U.S. application Ser. No. 11/231,063 all of which were previously incorporated by reference herein in their entirety, and will be described in greater detail below. 
         [0070]    Referring now to  FIG. 6 , there is shown an elevation view of a barrel assembly of the automatic firearm shown in  FIG. 1 . Referring also to  FIG. 7 , there is shown a partial section view of the barrel assembly shown in  FIG. 6 . Barrel  14  has radiator  116  assembled there to. In this embodiment, radiator  116  is an assembly of two substantially similar parts. As may be realized from  FIG. 2 , air may be forced from the receiver by the bolt assembly action, through grooves  146  in the barrel (illustrated for example purposes in  FIG. 6 ), and directed over the fins of radiator  116 . Referring also to  FIGS. 12 and 13 , Cooling holes or slots in the hand guard further aid convection cooling. Portions of radiator  116  may be fastened together, by screws  118  as an example. A bottom shield  120  may be removably mounted to radiator  116  to protect the hand of the user grasping the guard. The shield may be of any desired size and shape. The shield may be made of sheet metal curved to conform generally to the inside of guard  46 . As noted before, the barrel nut assembly generally has a barrel nut  92  and an outer collar  86  threaded onto the barrel nut. Here, the barrel nut has external threads  94  that mate with corresponding thread  96  of the collar  86  for threading the outer collar. In order to engage the guards  44 ,  46 , the outer collar  86  is threaded in a forward direction  126  to engage guards  44 ,  46  and substantially clamp the rear end  88 ,  90  of the guards between collar  86  and flange  94 F of the barrel nut see also  FIG. 4 ). The notched end of the collar faces in a direction opposite of direction  26  to engage the locking pin in the receiver. 
         [0071]    Referring now to  FIG. 8A , there is shown a front view of a barrel nut  92 . Referring also to  FIG. 8B , there is shown a section view of a barrel nut. Barrel nut  92  has external threads  94  that mate with corresponding thread  96  of the collar  86  for threading the outer collar. Flange  94 F is disposed to form a seating surface for the front facing surface of the rear end  88 ,  90  of the hand guards  44 ,  46 , against which the rear end abuts when clamped by the outer collar  86  as previously described. In the exemplary embodiment, the barrel nut may include a seating detent  92 R for the spring stop  50 T of the gas system. The stop  50 T may be held by detent  92 R and the upper hand  65  and substantially as shown in  FIG. 4 . 
         [0072]    Referring now to  FIG. 9A , there is shown a front view of a barrel nut collar. Referring also to  FIG. 9B , there is shown a section view of a barrel nut collar. The outer collar  86  threads onto the barrel nut. The external threads  94  of the barrel nut mate with corresponding internal thread  96  of the collar  86 . As noted before, the spring loaded pin  102  (see  FIG. 2 ) engages a saw tooth feature  104  on the collar  86  to prevent rotation of the collar  86  after locking the hand guards  44 ,  46  in position. Outside diameter  156  of collar  86  may be knurled in order to allow the operator to better rotate collar  86  for hand guard removal. An annular chamfer  158  may be provided in collar  86  to prevent point contact of collar  86  with the V-grooves in the rear end  88 ,  90  of the hand guard sections. 
         [0073]    Referring now to  FIG. 10A , there is shown an elevation view of an upper receiver  44 . Referring also to  FIG. 10B , there is shown a front view of an upper receiver  44 . Referring also to  FIG. 10C , there is shown a partial section view of an upper receiver  36 . As noted before, in the exemplary embodiment, the upper receiver may be provided with a manual lock actuator  100  to lock the collar  86  in place after rotation of the collar  86 . In the embodiment shown, the manual lock  100  comprises a spring loaded pin  102 , biased forwards that engages the collar  86 . Spring loaded pin is spring loaded by spring  160  located in bore  162 . Thumb pad  164  or any other suitable manual grip may be provided to pull actuator/spring loaded pin  102 , locking the actuator  100  into the open position against the spring bias of second spring loaded detent  166  as previously described. 
         [0074]    Referring now to  FIG. 11A , there is shown a bottom view of an upper hand guard  44  in accordance with an exemplary embodiment. Referring also to  FIG. 11B , there is shown a side view of the upper hand guard. Referring also to  FIG. 11C , there is shown a top view of the upper hand guard, and in  FIG. 11D , there is shown an end view of the upper hand guard. As shown in  FIG. 2 , and noted before, cap  66  may be provided on barrel  14  to interface with the front  68  of the removable hand guard section  44 . In the exemplary embodiment guard  44  and cap  66  may have complementing conical tapered, radially locating features  68 ,  124  (see also  FIG. 13B ) that fix the hand guard, eliminating lateral and longitudinal play in the guard mount. In alternate embodiments, the guard mounting to the cap and barrel could have any other radially locating and/or fixing features engaged by longitudinal displacement of the guard. As noted before, the upper  44  guard and cap  66  may have interlocking facets, for example, in the embodiment shown, a pin  72  and hole  76  system for rotational positioning. In alternate embodiments, other surfaces, for example, conical surfaces may be provided for radial fixing and/or may be added to pins and holes to simultaneously locate and lock the hand guards in position both in both axial, radial and rotational direction. As previously described, the rear portion  80  of the hand guard is removably attached to the receiver  36 . In the embodiment shown, the rear of the hand guard may have walls or flanges for attachment of the upper  44  hand guard to the receiver  36  that have tapered radial interlocking rabbett fit between a barrel nut collar  86  and a V-groove  88 V at the rear  80  of the guard  44 . Here, the v-groove  88 V at the rear of the guard interfaces with the barrel nut assembly to removably lock the guards in place. A rear tab  110  on the hand guard upper rail engages a mating slot  112  on upper receiver rail similar to U.S. application Ser. No. 11/231,063 previously incorporated by reference in its entirety. Holes  440  may be formed along the sides of the hand guard allowing for fastening of accessory devices (with screws or pins) to the hand guard. 
         [0075]    Referring now to  FIG. 12A , there is shown a side view of a lower hand guard. Referring also to  FIG. 12B , there is shown a top view of a lower hand guard. Referring also to  FIG. 12C , there is shown an end view of a lower hand guard. The lower hand guard is generally similar to that shown in U.S. application Ser. No. 11/231,063 previously incorporated by reference in its entirety. In the exemplary embodiment, the lower hand guard  46  may have a rounded bottom grip surface. The lower hand guard  46  as noted before may have multiple fastener and/or accessory mount locations for mounting accessories, for example a handgrip, grenade launcher or otherwise. The lower hand guard has multiple fastener holes that allow for mounting of accessories, for example, mounting of grenade launcher to lower guard or other accessories. As previously noted, cap  66  is provided on barrel  14  and interfaces with the front  70  of the removable hand guard section  46  in a manner substantially similar to that described for upper hand guard  44 . Guard  46  and the cap  66  have complementing conical tapered radially locating features  70 ,  124  that fix the hand guard, eliminating play in the guard mount. In alternate embodiments, the guard mounting to the cap and barrel could have any other radially locating and/or fixing features engaged by longitudinal displacement of the guard. The lower  46  guard and cap  66  have interlocking facets, for example, in the embodiment shown, a pin  74  and hole  78  system for rotational positioning. In alternate embodiments, other surfaces, for example, conical surfaces may be provided for radial fixing and/or may be added to pins and holes to simultaneously locate and lock the hand guards in position both in axial, radial and rotational directions. The rear portions  82  of the hand guard is generally similar to the rear end portions  80  of the upper hand guard for removably attaching the rear of the hand guard  46  to the receiver  36 . In the embodiment shown, wall sections  90  for attachment of the lower  46  hand guard to the receiver  36 , have a tapered radial interlocking rabbett fit between a barrel nut collar  86  and a V-groove  90 V at the rear  82  of the guard  46 . Here, the v-groove  90 V at the rear wall  90  of the guard interfaces with the barrel nut assembly to removably lock the guards in place as previously described. 
         [0076]    Referring now to  FIGS. 13A-13B , there is shown respectively an end view and section view of the end cap  66 . As noted before, cap  66  is provided fixed on barrel  14  and interfaces with the front  68 ,  70  of the removable hand guard sections  44 ,  46  As described (e.g. the guards  44 ,  46  and the cap  66  have complementing conical tapered radially locating features  68 ,  70  that mate with conical feature  124  of cap  66  that fix the hand guards, eliminating play in the guard mount). 
         [0077]    Referring now to  FIG. 14A , there is shown an end view of alternate embodiment sight  210 . Referring also to  FIG. 14B , there is shown a side view of alternate embodiment sight  210 . Referring also to  FIG. 14C , there is shown an isometric view of alternate embodiment sight  210 . Referring also to  FIG. 14D , there is shown an isometric view of alternate embodiment sight  210  with cylinder  214  removed. Referring also to  FIG. 16A , there is shown a front view, partially in section of alternate embodiment sight  210  with cylinder  214  removed. Referring also to  FIG. 16B , there is shown a side view, partially in section of alternate embodiment sight  210  with cylinder  214  removed. Referring also to  FIG. 16C , there is shown a rear view, partially in section of alternate embodiment sight  210  with cylinder  214  removed. Front sight assembly  210  generally comprises gas block  216 , sight portion  234  and a spring loaded pivot or detent assembly  236 . Assembly  236  has post  240  and spring  242  biasing the post  240  in a locked position. Post  240  has a tapered rectangular feature that positively seats in a mating rectangular recess  246  of block  216  (see  FIG. 17A ). Post  240  also has a slot that cooperates with pin  244  of sight  234  such that as post  240  is rotated, sight  234  is also rotated. To lower sight  234 , post  240  is pressed in against spring  242  and disengaging rectangular feature  246  allowing sight  234  to be rotated to a lowered position. As noted before, in alternate embodiments, the firearm may be provided with a one piece upper receiver with integral hand guard, and with an indirect gas operating system facilitating automatic or semi-automatic operation. Such a receiver, hand guard and operating system is disclosed in U.S. patent application Ser. No. 11/154,738 filed Jun. 16, 2005 and U.S. patent application Ser. No. 11/352,036 filed Feb. 9, 2006; both of which were previously incorporated by reference herein in their entirety. In the exemplary embodiment shown in  FIGS. 14A-14C  a gas block  216 , may have a removable cylinder  214  therein. The gas block  216  is fitted to barrel assembly  14  where barrel assembly  14  has a bore with the cylinder being in fluid communication with the bore through a port. A piston and rod assembly  50  (see  FIG. 2 ) having a piston and an operating rod  500  may be housed within the hand guard of the upper receiver (in a manner similar to that shown in  FIG. 4 ). The piston is fitted to removable cylinder  214 . The barrel has a bore  14 BB for exhausting firing gases. The cylinder  214  in the gas block has a port in fluid communication with the bore through a port  216 P (See  FIG. 17D ) disposed on a surface of the gas block  216  facing the barrel. The piston and rod assembly  50 P housed within hand guard and receiver when mounted to the firearm cooperate with the gas block  216  and cylinder  214  where piston  50  is movably fitted to the cylinder  214 . In alternate embodiments, other suitable assemblies may be used, for example, where the piston and rod are of two piece or unitary construction. Gas block  216  has a bore  222  that houses cylinder  214 . In alternate embodiments, the indirect gas operating system may have valving or pressure regulator to allow the user to select a desired operating pressure, for example, to change the firing rate. Examples of such regulators are disclosed in U.S. Patent Applications 60/610,703 filed Sep. 17, 2004 and 11/231,063 filed Sep. 19, 2005, both of which were previously incorporated by reference herein in their entirety. In the embodiment shown, the indirect gas operating system incorporates a quick removable gas piston cylinder  214 , where the cylinder sleeve  214  may be removable from the front of gas block  216  and therefore removable from the front of the receiver or rail. Upon removal of sleeve  214 , the piston and operating rod may similarly be removed from the firearm without further disassembly, for example to allow for cleaning and maintenance without further disassembly. Removable gas piston cylinder sleeve  214  is maintained captive with takedown pin  212  below piston cylinder sleeve  214  engaging slot  224  (see  FIG. 20B ). The take down pin is held captive, for example, by the spring  226  and detent ball  228 . Indexing pin  230  is provided for aligning purposes, aligning piston cylinder sleeve  214  in proper angular orientation relative to gas block  216 . Gas ports  232  may be provided in the cylinder and/or the gas block  216 , for example the gas ports may be both gas intake port(s) and exhaust port(s). 
         [0078]    Referring now to  FIG. 15 , there is shown an isometric view of gas block  216 . Referring also to  FIG. 17A , there is shown a side view of gas block  216 . Referring also to  FIG. 17B , there is shown a partial section view of gas block  216 . Referring also to  FIG. 17C , there is shown a partial section view of gas block  216 . Referring also to  FIG. 17D , there is shown a partial view of gas block  216 . Referring also to  FIG. 17E , there is shown a partial section view of gas block  216 . Bore  222  is provided for the mounting of cylinder  214 . Port  216 P communicates with port  14   b  of barrel  14  and port  250  of cylinder  214 . In the exemplary embodiment, exhaust slot  252  and exhaust backcut  254  may be provided to communicate with exhaust port  232  (see  FIG. 19 ) of cylinder  214  such that as piston  50  passes port  232 , exhaust gasses are vented through port  232  via cut and port  254  and lateral exterior slot  252  towards the front of the rifle but offset from the centerline of piston  50  minimizing interference with sighting due to exhausted firing gases at the gas block. Bore  256  is provided to locate takedown pin  212  with bore  258  provided for retaining spring and ball  226 ,  228 . Backcut  260  is provided to allow sight  234  to clear gas block  216  during lowering or raising. 
         [0079]    Referring now to  FIG. 18 , there is shown an isometric view of take down pin  212 . Take down pin  212  has shaft  262  that interfaces with bore  256  of block  216  and back cut  224  of cylinder  214 , retaining cylinder  214  when engaged. Shoulder  266  prevents pin  212  from being pushed through block  216  while locating cuts  264  relative to ball detent  228  for retention in block  216 . Flat  268  is also provided. 
         [0080]    Referring now to  FIG. 19 , there is shown an isometric view of cylinder  214 . Referring also to  FIG. 20A , there is shown an top view of cylinder  214 . Referring also to  FIG. 20B , there is shown a section view of cylinder  214 . Cylinder  214  has lug  270 , bore  272  and alignment slot  274 . Lug  270  allows the cylinder  214  to be removed from bore  222  with tools if necessary, for example when fouled excessively. Bore  272  interfaces with piston  50 P and is sufficiently deep to allow piston  50 P to properly seat therein. Alignment slot  274  interfaces with pin  230  in order to prevent incorrect orientation of cylinder  214  within gas block  216 . Supply port  250  communicates with the barrel  14  via port  216 P in block  216 . Exhaust port  232  formed in the sidewall of the cylinder may be angled outward and toward the front or muzzle of the firearm to direct exhaust gasses there through to back cut  254  and slot  252  of block  216 . The combination of angled port  232 , back cut  254  and slot  252  provide forward facing exhaust whereby exhaust gas is exhausted gas away from the operator hands. 
         [0081]    It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances. 
         [0082]    Embodiments of the invention has been described above, but it will be apparent to a reader skilled in the art that alterations, modifications and variations can be effected to the particular embodiments without departing from the scope of the invention, which is defined solely by the claims appended hereto. For example, it will be understood by persons of ordinary skill in the art that the dimensions may be appropriately scaled for firearms of different calibers.