Patent GB-1507874-A (GB)
Title: Automatic weapons
IPC: F41A23/08
Filed: 1975-04-01
Abstract: 1507874 Automatic weapon BRUNSWICK CORP 1 April 1975 [25 April 1974] 13267/75 Heading F3C An automatic weapon comprises a receiver assembly 100 within which is slidably mounted along rods 134, 135 a spring buffered bolt assembly 600. The bolt assembly includes a guide pad which engages over the barrel during the last part of the forward movement of the bolt to guide the bolt and thus accurately seat the cartridge. A barrel assembly 200, comprising a muzzle 202, a tapered section 201 and a cylindrical section 211 containing a chamber, is mounted on the receiver by a pair of pawls carried by a bulkhead attached to the front of the receiver, which pawls engage locking lugs 217, 218 carried by the barrel assembly. A stack is mounted to the rear of the assembly by pins 712, 713 which serve also to secure a handle 803. Located adjacent the handle is a trigger assembly 700 including a safety latch and located in advance of the trigger assembly is a cartridge feed assembly 300 which receives cartridges from either a remote magazine box (as in Fig. 1) or a magazine box 403 secured to the gun (see Fig. 2). The feed assembly is driven by an actuating assembly 500 (see Figure 26 and 27) to present in succession cartridges to a feed ramp (see Fig. 12). The activating assembly is in turn driven by the bolt and the bolt carries a projection to push the cartridges from the feed assembly along the ramp and into the chamber. The bolt also carries a firing pin to fire the cartridges as they seat in the chamber. A fixed rear sight 103 is provided together with a foresight 102 which is manually movable along a slot 128 in the receiver to move the bolt back and charge or cock the gun. The weapon may be used as shown in Fig. 1 with tripod legs as a machine gun, with bipod legs as shown in Fig. 2 as a sub-machine gun, or with a stock such as shown in Fig. 47 for firing from the prone position. The various components of the gun are slotted into place to effect easy assembly and dismantling of the gun. The receiver assembly. The receiver assembly 100 includes a channel shaped stamped apertured metal receiver 101 having a plastics mounted rear sight 103 and a front sight 102 mounted upon a plastics member 132 slidable in a slot 128 in the receiver. The rear end 133 of the member 132 engages a slot in the bolt so that the weapon can be cocked by pulling the front sight back. The receiver has a pair of flanges 150 midway along its length to which is mounted a feed ramp 178 (see Fig. 12) having a channel 187, 188 along which cartridges are fed and having projecting studs which secure it in place between the feed assembly 300 and the rear of the barrel hand grip 203. The bolt assembly 600 is slidable within the receiver along guide rods 134, 135, a buffering spring 656 being located between the assembly and a rear plate 828. The forward end of the receiver carries a bulkhead 139 firmly riveted to it. The bulkhead includes a pair of spring pawls 162, 165 pivoted to one side of it and a notched locking member 153 pivoted to the other side. The locking member carries tabs 155, 156 which engage slots 136, 137 in the front ends of the guide rods 134, 135, which project through apertures 147, 147<SP>1</SP> in the bulkhead. The pawls are adapted to engage below the rear lug 217 of a pair of lugs 217, 218 machined on to the barrel 201 to secure the barrel to the receiver. Both bulkhead and locking member have a cut-out 152, 154 which is received between the lugs. A pair of bipod legs (see Fig. 2) of uniform cross-section and having flat ground contacting bases 113, 114 can be pivoted to flanges 108, 109 located at the forward end of the receiver. The legs may be retained in a raised position by reception of the bases by spring plunger catches mounted upon the feed ramp. An alternative bulkhead assembly 1300 (see Fig. 55) comprises a bulkhead plate 1301 of several layers of high tensile steel. The plate has pivot holes for the sprung barrel retaining pawls and the locking member and has a pair of bipod support tabs 1319 and 1325 welded to it the tab having various notches 1328, 1329, 1330 to hold the supports in various positions. Backwardly directed legs 1310-1313 are provided to attach the bulkhead to the receiver. Barrel and bolt actuating assembly. The barrel comprises a tapered portion 201 having a muzzle 202 at one end, a cylindrical portion 211 at the other and a bore 216. A perforated hand grip 203 is carried by the cylindrical portion and a firing chamber is located at the rear of the bore in the cylindrical portion. The firing chamber comprises a main chamber 213 having a longitudinally grooved section 231 and an ungrooved section behind it. The grooved section connects with a smaller grooved section 215<SP>1</SP> via a tapering section 214 and the section 215<SP>1</SP> connects with an intermediate smoothwalled section 228 in communication with the rifled bore 216. Immediately after firing, the casing 1001 of a cartridge 100 in the chamber moves slightly rearwardly until it expands, under internal pressure of the combustion gases, into gripping contact with the chamber. Continuing build up within the casing causes the gases to flow along the grooves in section 231 to loosen the grip of this section and to cause a backward stretching of the casing which is still gripped by the ungrooved section of the main chamber. Further build up in the casing causes the gas in the grooved section to release the casing from the ungrooved section thus freeing the cartridge for bodily backward movement. The initial movement of the cartridge and the subsequent stretching are sufficient to overcome the inertia of the bolt and it is propelled away from the chamber helped in the last instance by the final bodily backward movement of the casing. The force exerted by the casing on the bolt and thus the bolt velocity can be easily controlled by adjusting the gripping action by altering the groove depth, groove length, projectile shape, and the material from which the projectile is made. A light-weight bolt is possible. The muzzle (see Fig. 15) is provided with slots 224, 225, 226 sloping backwardly at an angle X of 30 degrees. This ensures the gases moving down the barrel to impart a forward component to the barrel of approximately 1/3 of the sideways component. Thus the recoil of the barrel is reduced. Ammunition box. The ammunition box comprises a plastics body 403 having a transparent lower region 404. Secured to the box by studs which are releasably received in apertures at the rim of the box are a pair of handles 401, 402. The cartridge feed assembly 300 is secured to the box between the handles and effects mounting of the box on the gun. The handles in their raised position shown can be used to carry the gun and the box as a single entity. The ammunition feeding gap at the top of the box is sealed by a tear off strip of "MYLAR" (Registered Trade Mark). Feeding mechanism.-The feed advance assembly 300 comprises a metal housing 302 secured by lugs 304 (not shown) and 305 to the feed ramp 178 and the feed advance mechanism 500 (see Fig. 26). Rotatably mounted within the housing is a rotary feed member 320 having six longitudinal grooves 329 for receiving cartridges held together by clips c. The feed member is driven by a hexagonal aperture 321 engaged by a lug on a pawl 523 of the feed advance assembly activating device (see Fig. 26) and the member is indexed by the correct amount each rotation by spring biased ball 317 mounted in the housing and engaging detents 325 on the member. An aperture 318 is cut in the side of the housing 302 to allow for removal of the clip. The device 500 for activating the feed advance assembly 300 comprises a frame member 501 having a central bore 505 within which is rotatably mounted a pawl 523. A notch 524 in the rear end of the pawl 523 is engaged by a second pawl 518 which is spring biased clockwise to bias the pawl 523 to a projecting position. The pawl 523 is driven incrementally by a cam follower 530 which carries plates engageable in slots in the faces of the pawl (see Figs. 28, 30, not shown). The cam follower is itself driven by a sinuous cam groove in the lower surface of the bolt so that as the bolt retracts after firing the follower is rotated to drive the pawls 528 by one increment. When the bolt is reforwarded the ratchet nature of the connection between the follower and the pawl 523 leaves the pawl stationary. With each rotation of the pawl 523 its leading end engages the hexagonal aperture 321 in the feed member 320 and thus rotates the feed member. Bolt assembly and fire rate change device.-The bolt assembly comprises a lower portion 620 and upper portion 601 and a pair of guide portions 609, 609 which run over the barrel in the forward position of the bolt. The assembly reciprocates under the rearward action of the cartridge casing along part of guide rods 134, 135, a pair of compression springs 138, 138<SP>1</SP> being interposed over each rod between a buffer plate 828 and the bolt. The bolt is shown inverted in Fig. 54 and the underside of the lower portion 610 carries a sinuous cam groove 615 which drives the cam follower 530 to operate the feed advance assembly actuating device, a first projection 625 to engage a gear 705 to hold the bolt cocked when it has been pulled back by cocking right sight 103, and a second projection effective to push the cartridge from the feed assembly 800 and into the chamber 213 of the barrel along the channel 186 of the feed ramp. On the front face of the lower portion of the bolt is a recess 631 for receiving the rear of the cartridge. Located in a central bore of the recess is a firing pin 633 having a firing projection 634 and located in an off-centre bore is an ejection pin 640 spring biased proud of the recess. An arcuate slot 638 is formed in the wall of the recess 631 and contains a spring member 638<SP>1</SP>. In use after firing as the bolt mov