Abstract:
A non-firing rifle that emulates a semi-automatic or automatic rifle for training in procedures for safe handling, cleaning, and field stripping of such weapons. The non-firing rifle retains the upper receiver assembly, barrel assembly, and ammunition magazine of the emulated rifle, as well as some of the components of the lower receiver assembly of the emulated rifle, but substitutes a modified forging for the lower receiver forging of the emulated rifle. Unlike the lower receiver forging of the emulated rifle, the modified forging has no cutouts to allow a trigger or hammer to be installed. A cutout is provided in a bottom wall of the forging, however, to allow installation of a pseudo-trigger. Accordingly, it is incapable of firing a live ammunition round.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   None 
   STATEMENT REGARDING FEDERALLY APPROVED RESEARCH OR DEVELOPMENT 
   None 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to training firearms and, in particular, to automatic and semiautomatic rifles that have been modified so as to be unable to fire ammunition, but which retain enough of the features of an original equipment rifle as to be useful in training military and police recruits in rifle cleaning, safety, and field stripping procedures. 
   2. Background Art 
   Military and police personnel, especially raw recruits, require introductory training in the use of firearms. Such training typically will include instruction on safe handling and storage, as well as procedures for cleaning, and field stripping, of such weapons. In the interest of safety, training firearms for this purpose desirably are incapable of firing a lethal round, or of firing any round at all. It is still more desirable to provide for training and familiarization, a standard firearm with minimal modification to make it non-firing, whereby all the procedures ordinarily followed with the standard form of the firearm can be performed on the modified firearm. 
   U.S. Pat. No. 5,937,563 to Schuetz disclosed a firearms safety system for adapting conventional handheld firearms to fire non-deadly simulated training ammunition. The system provides a series of gas relief ports and passages to prevent the successful firing of live ammunition in the firearm. 
   U.S. Pat. No. 4,969,283 to Baehr disclosed a firearm having live round inhibiting means mounted in the barrel of the firearm, which permitted a blank cartridge to be loaded into a firearm and fired while preventing the loading and firing of a live round. 
   U.S. Pat. No. 6,625,916 to Dionne disclosed a conversion of firearms to fire reduced-energy ammunition. A training kit was provided for use with a firearm that normally has a standard bolt, which standard bolt had a bolt recess at a forward end thereof for receiving and embracing the head end of a standard cartridge. The training kit included, in addition to round of reduced-energy training ammunition, a training bolt with a circular recess of a diameter that would not receive and embrace the head end of the standard cartridge; this limited the placement of a standard cartridge beyond the reach of the firing pin. 
   To prevent inadvertent placement of a live round into a firearm equipped with a laser for use in laser tag training exercises (the Multiple Integrated Laser Engagement System or “MILES”), U.S. Pat. No. 7,036,260 to Gee disclosed a safety system for safely venting through a succession of vent holes in the barrel the pressure needed to propel a bullet down and through the barrel. If a live round were inadvertently loaded, the bullet would be retained in the bore and the firearm would shut down. 
   U.S. Pat. No. 6,973,863 to Jones disclosed an adaptor for use with a flash suppressor on a machine gun barrel that developed sufficient back pressure in order to allow the gun to repeatedly fire blank rounds of ammunition. 
   U.S. Pat. No. 6,701,909 to Tiberius et al. disclosed a semi-automatic-firing compressed gas gun for firing paintballs. The gun was sized and designed to appear like and operate in a manner similar to a conventional gun. 
   U.S. Pat. No. 6,869,285 to Jones, II disclosed a training firearm that provided a realistic recoil effect. A laser replaced live rounds, and a blow back assembly was provided that was driven by a disposable cartridge of compressed gas that was self-contained in the gun handle. A valve integrated with the firing pin released a burst of gas when the firing pin was impacted by the hammer. The gas pushed back a slide and recocked the hammer for the next round. 
   SUMMARY OF THE INVENTION 
   According to the present invention, a non-firing training rifle is provided by modification to an original equipment, manually operated, semiautomatic or automatic rifle of the kind that includes a lower receiver assembly, an upper receiver assembly housing a bolt carrier assembly and a charging handle, a barrel assembly, and an ammunition magazine insertable into the magazine well of the lower receiver assembly. This is achieved by modifications that are limited just to changes in the lower receiver assembly and, preferably, to a change in the rifle barrel also. In this manner, the training rifle, although incapable of firing a live round, has the look, feel and operability as near as possible to the original equipment rifle that it emulates. Of particular importance for training purposes, the following operations, when performed on the training rifle, are identical to those performed on the original equipment rifle that it emulates: rifle disassembly, cleaning, and reassembly; operation of the safety selector; attachment and disattachment of a bayonet; insertion and removal of an ammunition magazine; and height adjustment of the rear sight. 
   For the original equipment lower receiver assembly is substituted a modified lower receiver assembly that eliminates the firing chamber and eliminates the hammer. Whereas a rear portion of an original equipment lower receiver is open at the top to permit the hammer, when actuated by a trigger assembly, to strike a firing pin within the upper receiver portion so as to cause the firing pin to impact an ammunition cartridge within the firing chamber and thereby fire a bullet, the modified lower receiver assembly of the present invention has a flat top wall located there instead. Thus, the training rifle is incapable of firing a live round. Preferably, for the standard equipment rifled gun barrel is substituted a smooth bore rifle barrel, which saves the unnecessary time and expense of rifling the gun barrel. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a right side elevational view of the training rifle of the present invention that emulates an M-16 rifle, wherein, for clarity, the sling has been removed and the upper receiver assembly (with attached barrel assembly) and the ammunition magazine are shown disattached from the lower receiver assembly, but aligned and oriented preparatory to attachment to the lower receiver assembly. 
       FIG. 2  depicts in exploded view the bolt and carrier assembly, upper receiver assembly, barrel assembly and lower receiver assembly of an unmodified, prior art M-16 rifle; 
       FIG. 3  is a left side, top perspective view of a lower forging thereof, removed and stripped; 
       FIG. 4  is a top view thereof; 
       FIG. 5  is a right side elevational view thereof; and 
       FIG. 6  is a bottom view thereof. 
       FIG. 7  is a left side elevational view of the training rifle of the present invention that emulates an M-16 rifle; 
       FIG. 8  is a top, left side perspective view of the lower receiver assembly thereof; and 
       FIG. 9  is a right side elevational view thereof. 
       FIG. 10A  depicts a trainee disattaching an ammunition magazine from the training rifle. 
       FIG. 10B  depicts a trainee visually checking that the firing chamber is clear. 
       FIG. 10C  depicts a trainee, after finding that the firing chamber is clear, putting the safety selector to the “Safe” position. 
       FIG. 11A  depicts a trainee removing the strap of the sling from the training rifle. 
       FIG. 11B  depicts a trainee removing the handguards from the training rifle. 
       FIG. 12A  is an enlarged, fragmentary, right side elevational view of the training rifle, and the upper receiver assembly has been pivoted away from the lower receiver assembly, as an initial step in field stripping the training rifle; 
       FIG. 12B  depicts partial removal of the charging handle and carrier bolt assembly therefrom; and 
       FIG. 12C  depicts a trainee lowering the charging handle thereof out of its track, as further steps in field stripping the training rifle. 
       FIG. 13A  depicts a trainee releasing the buffer and buffer spring from the extension tube of the training rifle; and 
       FIG. 13B  depicts removal of the buffer and buffer spring therefrom. 
       FIG. 13C  depicts removal of the firing pin retaining pin from the bolt carrier of the training rifle. 
       FIG. 13D  depicts removal of the bolt cam pin by turning it one-quarter of a turn. 
       FIG. 13E  depicts removal of the bolt out of the bolt carrier. 
       FIG. 14A  is a right side elevational view of the trigger of the prior art M-16 rifle. 
   

   As used herein, the terms “left,” “right,” “top,” and “bottom” refer to the left, right, top and bottom portions, respectively, of the training rifle as they would appear to a trainee who is holding it against his body in a ready-to-aim position. The terms “front” and “rear” refer to the right and left portions of the training rifle, respectively, as depicted in  FIG. 1 , and the term “forward direction” denotes a direction away from the buttstock and toward the front of the training rifle. Similar numerals denote similar components of the invention throughout the several figures. 
   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , the non-firing training rifle  100  of the present invention is shown partially disassembled and in right side elevational view, and may be seen to comprise an upper receiver assembly  110  with an attached barrel assembly  160 , a substitute lower receiver assembly  201  and an ammunition magazine  98 . M-16 is the U.S. military designation for a family of rifles derived from the Armalite AR-15 rifle and further developed by Colt Industries of Hartford, Conn., starting in the mid-20th century. It has been the primary infantry rifle of the United States military since the 1960s. Accordingly, for illustrative purposes, the non-firing training rifle  100  herein described emulates an M-16 rifle; but, it will be understood that the training rifle  100  can be altered within the scope of the appended claims in ways known to persons of ordinary skill in the art of manufacture of semi-automatic and automatic rifles in order to emulate other semi-automatic and automatic rifles. The upper receiver assembly  110 , barrel assembly  160 , and ammunition magazine  98  are standard equipment components of the original equipment rifle that the training rifle  100  emulates, and thus, for the training rifle  100  described and illustrated here, are standard equipment components of an M-16 rifle, as illustrated in  FIG. 2 ; provided that, unlike the rifled barrel of an M-16 rifle, the barrel  200  of the training rifle  100  preferably has a smooth bore. As depicted in  FIG. 1 , the upper receiver assembly  110 , with attached barrel assembly  160 , has been disattached from the lower receiver assembly  201  by removal of the rear takedown pin  88  from an apertured takedown pin lug  304  that depends from a rear, bottom end of the upper receiver assembly  110  and from a rear takedown pin aperture  88 A in the lower receiver assembly  201 , and further, by removal of the front pivot pin  74  from a transversely spaced-apart pair of apertured lugs  307  that extend forwardly from a front end of the lower receiver assembly  201  as well as from an apertured lug  306  that depends from a front, bottom end of the upper receiver assembly  110  and is adapted for insertion between the lugs  307 . 
   The training rifle  100  is further depicted fully assembled in left side elevational view in  FIG. 7  with the ammunition magazine  98  inserted into the magazine well  198  of the lower receiver assembly  201 . Attached to the barrel  200  in the normal manner are a flash suppressor  41 , delta ring assembly  302 , upper and lower handguards  66 , and a barrel nut  25  with internal thread for threaded attachment to a front end of the upper receiver assembly  110 . The delta ring assembly  302  includes a front sight  308 , and depending from the delta assembly are a bayonet lug  103  and front sling swivel  85 . Inserted within a longitudinally-extended tubular housing  310  of the upper receiver assembly  110  are a bolt and bolt carrier carrier assembly, overlying which is a charging handle  20  supported within a longitudinally-extended track  312 , all as depicted in  FIG. 2 . Extending upward from the track  312  is a carrying handle  314 . A rear sight  19  is incorporated into a rear portion of the handle  314 , which includes a screw height adjustment  300 . All these components of the barrel assembly  160  and upper receiver assembly  110  are standard equipment on an M-16 rifle, depicted in  FIG. 2 . 
   The lower receiver assembly  201  of the training rifle  100  comprises some, but not all, of the components of an M-16 lower receiver assembly as depicted in  FIGS. 2-6 . Retained within the lower  201  assembly of the training rifle  100  are the original equipment pistol grip  71 B, buttstock  15 , receiver extension  15 C, buttstock buffer  15 B, buffer spring  15 D, stock spacer  15 F, buffer detent  12 , buffer detent spring  13 , safety selector  82 , safety detent  83 , safety spring  84 , front pivot pin  74 , rear takedown pin  88 , bolt catch  7 , magazine catch  68 , magazine catch spring  69 , magazine catch button  70 , ejection cover  32 , ejection cover spring  33 , ejection cover hinge plate  34 , ejection cover hinge pin clip  35 , and trigger pin  64 . Eliminated from the training rifle  100  are the following components of an M-16 lower receiver assembly: trigger  91 , hammer  63 , hammer pin  64 , and hammer spring  65 . A pseudo-trigger  91 ′ is substituted for the trigger  91 . The original equipment trigger  91  has a front, lever end  91 F that engages a hammer  63  and a rear, lever end  91 R that engages the safety selector  82  within the cutout  101 C of the prior art forging  101 PA, but these features are preferably eliminated in the pseudo-trigger  91 ′ as unnecessary. Substituted for the original equipment lower receiver forging  101 PA, as depicted in  FIGS. 2-6 , is a modified lower receiver forging  101  to which the aforementioned retained components are attached in a manner identical to the way they are attached to the original equipment lower receiver forging  101 PA. The forging  101  is preferably fabricated of forged aluminum, but other suitable substances and fabrication methods could be employed to make this component of the training rifle  100 . 
   The modified structure of the substituted lower receiver forging  101 , as depicted in  FIGS. 8 ,  9 ,  10 A,  10 B and  10 C, should be compared with the prior art lower receiver forging  101 PA as depicted in  FIGS. 2-6 . It may be seen that both versions extend longitudinally from a rear end to a front end and include a rear portion  101 R comprising buttstock attachment means by which the forging is attached to a front end of the buttstock  15 , which means includes an upstanding, internally threaded ring  320  having an internal diameter slightly greater than the diameter of the buffer  15  for mating engagement with the external thread on a front end portion of a receiver extension  15 C. Both versions have a front portion  101 F comprising spaced-apart, vertical left and right walls  330 L,  330 R of equal size joined by a first vertical front wall  332 , and a central portion  101 C intermediate the rear and front portions, said central portion including longitudinally-extended left and right walls  340 L,  340 R of equal size joined by a second vertical front wall  350 , a bottom wall  360  and the buttstock attachment means  320 . In the prior art lower receiver forging  101 PA, the central portion  101 C has a top cutout  101 D so that it is open at the top to permit the hammer  63  to strike the firing pin  39  when the trigger  91  is pulled. In the lower receiver forging  101  of the training rifle  100 , the central portion  101 C includes a flat, longitudinally-extended horizontal top wall  370  that joins the upper margins of the left wall  340 L and the right wall  340 R, and a flat bottom wall  335  that joins lower margins of the same walls, whereby the central portion  101 C fully encloses an interior space, except for an opening  371  in a rear end portion of the top wall  370  adapted to receive the takedown pin lug  304  of the upper receiver assembly  110 , and except for a pseudo-trigger access cutout  91 C in the bottom wall  335 , which bottom wall  335  and cutout  91 C are identical to those of the prior art forging  101 PA as depicted in  FIG. 4 , the cutout  91 C being only somewhat larger in the training rifle  100  compared to that of the prior art M-16 rifle. Thus, the cutout  101 D of the prior art forging  101 PA is eliminated in the substitute forging  101 , but the bottom wall  335  and trigger access cutout  91 C are retained. Suitable apertures are provided in the left and right walls  340 L,  340 R of the central portion  101 D for mounting a magazine catch button  70 , a trigger pin  64 , a safety selector  82 , and for receiving the rear takedown pin  88 . At a front end of the substitute lower receiver forging  101 , apertured lug extensions  307  are provided for attachment of a front end of the upper receiver assembly  110  to a front end of the lower receiver forging  101  by front pivot pin  74 . As in the prior art lower receiver forging  101 PA, the front portion  101 F includes a magazine well  198  into which an ammunition magazine  98  is insertable. The magazine well  198  is a space defined by the left and right walls  330 L,  330 R joined by the walls  332 ,  350 . Interior surfaces of the walls  332  and  350  have vertical slots  332 S and  350 S, which complementarily engage front and rear walls of an inserted ammunition magazine  98 , respectively. An upper end of the wall  350  has a transverse slot  7 S and an exterior surface of the left wall  340 L of the central portion  101 C has as a pair nibs  7 N, which, in combination, are adapted to receive and mount a bolt catch  7  to the lower receiver forging  101 . Depending from the central portion  101 C is a trigger guard, which is identical to the trigger guard of the prior art lower receiver forging  101 PA, and comprises a front guard member  170 F with an arcuate rear surface and a rear guard member  170 R with an arcuate front surface joined at their lower ends by a straight, flat lower member  170 L. Integral with, and rearward of, the rear guard member  170  is means  180  for attaching an upper portion of the pistol grip  71 B to a lower portion of the lower receiver forging  101 ; said means includes a longitudinally-disposed plate  190  that depends from the bottom wall  360  of the central portion  101 C, and which appears substantially trapezoidal in left and right side elevational views. The plate  190  is complementary to, and is received by, a recess  184  in an upper end portion of the pistol grip  71 B and has an internally-threaded aperture  182  for attachment to the pistol grip  71 B by a threaded bolt  72 , as depicted in  FIG. 2 . Thus, the means of attachment of the pistol grip  71 B to the lower receiver forging  101  is identical to that of the prior art M-16 rifle. 
   The training rifle  101  may be used to demonstrate and to practice rifle clearing, cleaning, safety, and field stripping procedures. The procedure to check that the firing chamber is clear is as follows. The ammunition magazine  71 B is removed by pressing the magazine catch button  70  and pulling the magazine out of the magazine well  198 ;  FIG. 10A . The rifle muzzle is placed into a cleaning barrel; if one is not available, the muzzle is pointed into the air. The charging handle  20  is pulled back, and the bottom of the bolt catch  7  is pressed to lock the bolt  3  to the rear. With the ejection cover hinge plate  34  open, the firing chamber is visually checked through the ejection port  14  to see whether the firing chamber is clear;  FIG. 10B . If the firing chamber is clear, the safety selector is then moved to the “Safe” position;  FIG. 10C . 
   Field stripping of the training rifle  100  proceeds as follows. The strap  61  of the rifle sling is removed from the rifle;  FIG. 11A . The rifle  100  is made to stand on its buttstock  25 . To remove the handguards  66 , the slip-ring  316  must be depressed by another person or by use of a tool. With the slip-ring  316  depressed, one-half of handguards  66  is pried out of the delta ring assembly  302 , and then the other half out as well;  FIG. 11B . The rear takedown pin  88  is removed from its aperture  88 A and the rifle  100  is pivoted open about the front pivot pin  74 ;  FIG. 12A . The charging handle  20  is pulled out about half way (the bolt carrier assembly should come out with it);  FIG. 12B . The bolt carrier assembly  4  is pulled out. The charging handle  20  is pulled about three-fourths of the way out and lowered out of its track;  FIG. 12C . The bolt carrier assembly  4  and charging handle  20  are set aside. The front pivot pin  74  is pushed out and the upper receiver assembly  110  is separated from the lower receiver assembly  201 ;  FIG. 1 . The buffer detent  12  is pushed to release the buffer  15 B and buffer spring  15 D, which are then pulled out of the receiver extension tube  15 C within the buffer bore  318  of the buttstock  15 ;  FIGS. 13A ,  13 B. To disassemble the bolt carrier assembly  4 , the bolt  3  is pushed into the carrier  4 , and the firing pin retaining pin  40  is removed;  FIG. 13C . The bolt cam pin  16  is removed by turning it one-fourth of a turn and then pulling it out;  FIGS. 13D ,  13 E. The bolt  3  is then pulled out of the carrier  4 ;  FIG. 13E . To reassemble the training rifle  100 , just reverse the steps used to field strip the rifle. 
   From the foregoing description, it will be clear that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Thus, the presently disclosed embodiments are to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description. The term “forging,” wherever it appears in the claims, will be understood to include a component part of a lower receiver assembly of the kind herein described and illustrated and referred to above as a “forging,” which component part may be, but need not be, comprised of forged aluminum or other metals and which may instead be fabricated by machining, molded of plastic or made by other methods known to persons of ordinary skill in the design and manufacture of semi-automatic and automatic rifle components. 
   Part # Part Name 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               Part # 
               Part Name 
             
             
                 
                 
             
           
           
             
                 
                1 
               barrel nut 
             
             
                 
                2 
               upper receiver assembly, stripped 
             
             
                 
                3 
               bolt 
             
             
                 
                4 
               bolt carrier 
             
             
                 
                5 
               bolt carrier key 
             
             
                 
                6 
               bolt carrier key screw 
             
             
                 
                7 
               bolt catch 
             
             
                 
                7S 
               slot in forging for bolt catch 
             
             
                 
                7N 
               pair of nibs on left wall of forging for bolt catch 
             
             
                 
                8 
               bolt catch plunger 
             
             
                 
                9 
               bolt catch roll pin 
             
             
                 
                10 
               bolt catch spring 
             
             
                 
                11 
               bolt gas rings, set 
             
             
                 
                12 
               buffer detent 
             
             
                 
                13 
               buffer detent spring 
             
             
                 
                14 
               ejection port 
             
             
                 
                15 
               buttstock 
             
             
                 
                15B 
               buttstock buffer 
             
             
                 
                15C 
               receiver extension tube 
             
             
                 
                15D 
               buffer spring 
             
             
                 
                15E 
               buttstock screw 
             
             
                 
                15F 
               stock spacer 
             
             
                 
                16 
               cam pin 
             
             
                 
                17 
               cap handguard front (round) 
             
             
                 
                18 
               cap handguard front (triangular) 
             
             
                 
                19 
               rear sight 
             
             
                 
                20 
               charging handle 
             
             
                 
                21 
               bolt carrier assembly 
             
             
                 
                22 
               charging handle latch 
             
             
                 
                23 
               charging handle latch roll pin 
             
             
                 
                24 
               charging handle latch spring 
             
             
                 
                25 
               delta ring 
             
             
                 
                26 
               disconnector 
             
             
                 
                27 
               disconnector spring 
             
             
                 
                28 
               ejector 
             
             
                 
                30 
               ejector spring 
             
             
                 
                31 
               ejector roll pin 
             
             
                 
                32 
               ejection cover 
             
             
                 
                33 
               ejection cover spring 
             
             
                 
                34 
               ejection cover hinge plate 
             
             
                 
                35 
               ejection cover hinge pin clip 
             
             
                 
                36 
               extractor 
             
             
                 
                37 
               extractor pin 
             
             
                 
                38 
               extractor spring with insert 
             
             
                 
                39 
               firing pin 
             
             
                 
                40 
               firing pin retaining pin 
             
             
                 
                41 
               flash suppressor 
             
             
                 
                42 
               flash suppressor lock washer 
             
             
                 
                44 
               forward assist retainer pin 
             
             
                 
                45 
               forward assist spring 
             
             
                 
                50 
               gas tube 
             
             
                 
                61 
               sling strap 
             
             
                 
                62 
               front swivel pin 
             
             
                 
                63 
               hammer 
             
             
                 
                64 
               hammer and trigger pin 
             
             
                 
                64A 
               trigger pin aperture 
             
             
                 
                65 
               hammer spring 
             
             
                 
                66 
               handguards 
             
             
                 
                68 
               magazine catch 
             
             
                 
                69 
               magazine catch spring 
             
             
                 
                70 
               magazine catch button 
             
             
                 
                71B 
               pistol grip 
             
             
                 
                72 
               pistol grip screw 
             
             
                 
                73 
               pistol grip screw washer 
             
             
                 
                74 
               pivot pin, front 
             
             
                 
                82 
               safety selector 
             
             
                 
                82A 
               aperture in forging for safety selector 
             
             
                 
                82B 
               safety selector stop 
             
             
                 
                88 
               takedown pin 
             
             
                 
                83 
               safety detent 
             
             
                 
                84 
               safety spring 
             
             
                 
                85 
               swivel, front 
             
             
                 
                86 
               swivel pin 
             
             
                 
                87 
               swivel, rear 
             
             
                 
                88 
               takedown pin, rear 
             
             
                 
                91 
               trigger 
             
             
                 
                91′ 
               pseudo-trigger 
             
             
                 
                91C 
               forging cutout for trigger 
             
             
                 
                95 
               weld spring 
             
             
                 
                96 
               lock ring 
             
             
                 
                98 
               ammunition magazine 
             
             
                 
               101 
               lower receiver forging 
             
             
                 
               103 
               bayonet lug 
             
             
                 
               110 
               upper receiver assembly 
             
             
                 
               123 
               upper receiver cylindrical extension 
             
             
                 
               160 
               barrel assembly 
             
             
                 
               198 
               magazine well 
             
             
                 
               200 
               barrel 
             
             
                 
               100 
               non-firing training rifle 
             
             
                 
               101 
               lower receiver forging of non-firing training rifle 
             
             
                 
               101PA 
               lower receiver forging of M-16 rifle 
             
             
                 
               201 
               lower receiver assembly 
             
             
                 
               300 
               Rear sight screw adjustment 
             
             
                 
               302 
               delta ring assembly 
             
             
                 
               304 
               take down pin lug 
             
             
                 
               306 
               pivot pin lug 
             
             
                 
               307 
               pair of apertured lugs on lower receiver forging 
             
             
                 
               308 
               front sight 
             
             
                 
               310 
               tubular housing of upper receiver assembly 
             
             
                 
               312 
               charging handle track 
             
             
                 
               314 
               carrying handle 
             
             
                 
               316 
               slip-ring 
             
             
                 
               318 
               buffer bore