The rear corners of the bolt supports are rounded so as to aid by their camming action the raising of the bolt lock (80). The inner edges of the bolt supports are formed to guide the cartridge into the chamber as it is stripped from the magazine. The locking shoulder of the receiver is located just in rear of the top plate. This shoulder supports the bolt lock and bolt when the cartridge is fired.

The bottom of the receiver is left open to receive the magazine at the front end. The rear portion of the opening is closed by the trigger guard (10), which fits up between the sides of the receiver. The rear end of the trigger guard is supported by a tongue in the receiver, which fits into a corresponding groove in the trigger guard. The forward end of the trigger guard is held in place by the trigger guard retaining pin (11). The trigger guard retaining pin spring (12) locks in an indentation in the receiver, thus holding the pin in place.

The ejector (29) is retained in a T-cut at the front end of the trigger guard by means of the ejector lock (30) and spring (31). The top of the ejector extends upward in such a way as to operate in the ejector cut in the bolt. The magazine catch (32) is pinned to the trigger guard. The upper end projects through the ejector, and provides a catch which holds the magazine in place. The magazine catch spring (33) is positioned between the ejector and the magazine catch, below the pivot point of the latter. This holds the upper end of the magazine catch in the forward position. The magazine release extends forward from the trigger guard and operates against the lower end of the magazine catch, thus moving the upper end of the catch rearward when the release is pushed forward.

The trigger (13) is pivoted to the trigger guard by the trigger pin (14). The connector (16) fits loosely in the trigger, the lower notch riding on the connector pin (15). The upper edge of the connector comes in contact with the front end of the sear (23) when the trigger is raised. The cam surface in rear of this edge engages the corresponding surface of the sear carrier (25) if the change lever (17) has been set at "F." The sear (23) is pivoted near the rear end of the trigger guard by the sear pin (24) which passes through the trigger guard and the sear carrier (25), the holes in the trigger guard being slotted. The rear end of the sear is provided with a nose which engages the sear notch in the slide (45). The under surface of the front end of the sear engages the connector when it is raised by the action of the trigger. The sear spring (26) is held in grooves in the trigger guard. This spring is of the leaf type, the middle tongue bearing against the connector holding this latter part in position. The two outside tongues of the sear spring bear downward against the forward end of the sear.

The change lever (17) extends laterally through the trigger guard, being held in place by the front tongue of the change-lever spring (18). This tongue also engages in notches around the shaft of the change lever, thus holding the change lever in the various positions. The handle of the change lever extends upward along the left side of the receiver on which is marked the positions: "F" for semiautomatic fire, "A" for full automatic fire, and "S" for safety. The cuts and lugs on the underside of the change-lever shaft control the action of the trigger and connector, thus giving the classes of fire mentioned. The change-lever stop (20) in the receiver prevents the

change lever from being set at safety without intention. The change-lever spring (18) is held in the trigger guard by means of grooves. The sear stop (19) is assembled to the rear tongue of this spring. The sear carrier (25) is held in place at the rear end by the sear pin and at the front end by the trigger pin, the holes in the sear carrier for the trigger pin being slotted so as to allow a certain amount of movement of the sear carrier in a forward direction. This movement is arrested by the counterrecoil spring (28) which surrounds the spindle at the front end of the sear carrier, bearing against the front shoulder of the sear carrier and the opposite shoulder of the trigger guard. Thus, when a shock is imposed upon the sear it is transmitted to the sear carrier through the sear pin, which operates in slotted holes in the trigger guard. The trigger operates between the side walls of the sear carrier. The connector stop (27) is in the form of a pin passing between these side walls and forming a stop which prevents excessive forward movement of the connector.

The forward end of the receiver near the top is threaded to receive the barrel (60) which is screwed in tightly to the draw marks. The barrel is of plain, light construction, the large diameter at the breech end being carried well forward of the chamber. The chambering and rifling of the barrel are of the usual design for U. S. caliber .30, model 1906, ammunition. The gas port is provided on the underside of the barrel about 6 inches from the muzzle end. This port corresponds to a similar port in the gas cylinder tube bracket (56) which surrounds the barrel at this point, being held in place by the gas cylinder tube bracket pin (57). The gas port extends through this bracket, which is provided with a T-cut which retains the front end of the gas cylinder tube (52). The front-sight base (61) surrounds the muzzle end of the barrel. This carrier is held in place by the front-sight key (62) and the front-sight key pin (63). The front-sight blade (64), which is of the usual construction, dove-tails transversely into the top of the front-sight base. The front-sight blades vary in height in accordance with the requirements of targeting the rifle at the factory. After targeting, the blade is staked in place with a prick punch. The muzzle end of the barrel is threaded to receive the flash hider (154), which is of plain, tubular construction, provided with a hole at the rear end, which takes the combination tool.

The rear end of the gas cylinder tube (52) is held up into the receiver by the gas cylinder tube retaining pin (53), the spring of which locks in an indentation in the left side of the receiver. The tube provides a guide way for the gas piston (46), and is threaded at the front end to receive the gas cylinder (50). This end is notched to engage the gas cylinder lock (51). The ribs at the top engage the T-cut in the bracket of the barrel holding the gas ports in close contact. The shoulder at the rear end of the tube provides a stop for the front end of the slide (45). The lugs above this bear against the barrel. The rear portion of the barrel and gas cylinder tube are protected on the bottom and sides by a large wooden forearm (118), which is attached to the gas cylinder tube by means of the forearm screws, long (120) and short (119). The forearm escutcheon (131) is permanently seated in the forearm and acts as a nut for the forearm screw, long. The outside of the forearm is cut to provide a good gripping surface for the band.

The recoil spring guide head (42) engages retaining shoulders in the front end of the receiver. The rear surface of this head is checkered to

facilitate stripping and assembling. The recoil spring guide (41) is riveted into the head which forms the rear seat for the recoil spring (40). The rear portion of this spring is guided by the recoil spring guide, the front portion being retained in the hollow gas piston (46).

The front swivel bracket (145) clamps around the gas cylinder tube in front of the forearm. The link swivel, inner (148), and link swivel, outer (149), and the swivel (143) are attached to the front swivel bracket by the swivel screws (147) in the manner described for the butt swivel plate. The gas cylinder lock (51) fits in the transverse hole through the head of the gas cylinder (50). The cylinder is provided with three gas ports of varying size. These are located around the circumference of the cylinder wall, the position and size of each being indicated by circles marked on the cylinder head. The notches for the head of the gas cylinder lock are located so as to register the gas port in the cylinder, indicated by the circle marking nearest the barrel. The inside of the gas cylinder is recessed at the forward end to provide clearance for dirt and powder fouling.

b. The moving portions consist of the operating breech, and firing mechanisms.

The rings at the front of the gas piston (46) operate in the gas cylinder. The rear end of the piston threads loosely into the front end of the slide (45), and is held from rotation by the gas piston retaining pin (49). The piston is of hollow construction, the front end being closed by the gas piston plug (48) and a bearing for the forward end of the recoil spring being provided by the gas piston bushing (47).

The slide (45) extends rearward in longitudinal grooves in the receiver, clearance for the magazine being provided between the sides of the slide. The rear end of the slide is beveled slightly to form a parallel line of contact against the buffer. A sear notch is cut in the underside of the slide. The hammer (85) is held in the guides in the slide by the hammer pin (86), which also acts as the lower pivot for the bolt link (82). After the breech has locked, the front face of the hammer strikes the firing pin. The bolt link is pinned to the bolt lock (80) by the bolt link pin (83). The upper and rearward projection of the bolt link forms a bearing surface against which the bolt lock rests during the recoiling movement. This holds the rear end of the bolt lock up.

The rear locking surface of the bolt lock (80) bears against the corresponding surface of the receiver as the cartridge is ignited. The underside of the bolt lock is slotted, and a cam surface provided which engages the retracting cam of the firing pin (76). The front end of the bolt lock bears against the bolt (75) with which it is permanently hinged by means of the bolt lock pin (81). The bolt carries the firing pin (76), the retracting cam of the latter operating in the slot in the rear tail, or firing pin guide, of the bolt. The head of the firing pin extends rearward from this guide, and when struck by the hammer causes the firing pin point to project through the hole i. the front face of the bolt, thus igniting the cartridge, the base of which is supported by the face of the bolt. The extractor (77) and extractor spring (78) are positioned in a recess at the front end of the bolt so that the extractor will engage the rim of the cartridge as it is driven forward into the chamber. A lug on the extractor engages a groove in the recess in the bolt and prevents the extractor from pulling out to the front.

c. The magazine consists of four pieces: The magazine tube (108), base (109), follower (110), and spring (111). The magazine tube is formed to receive a staggered double row of cartridges. Magazines having a capacity of 20 rounds are issued to rifle companies, a 40-round magazine being used especially for antiaircraft fire. A notch is cut in the rear edge of the tube which engages the magazine catch. The upper lips of the tube are formed to facilitate feeding. The magazine follower operates upward against the cartridges under the action of the magazine spring, which is supported at the bottom by the magazine base. The construction of 40-round magazines is similar to the 20-round type, except the tube is deeper and is fitted with two springs separated by a spacer.

31. Forearm group.—a. To strip the forearm group, unscrew the forearm screws, long and short, and remove the wood forearm from the gas cylinder tube. The forearm escutcheon should never be removed from the forearm. Unscrew the two swivel screws which allow the removal of the gun sling swivel, and the swivel link, inner and outer. Spring the front swivel bracket off over the gas cylinder tube.

b. Before removing the gas cylinder note its setting carefully, so that it can be reassembled to the same position. Then force out the gas cylinder lock until its head clears the notch in the gas cylinder, which can then be unscrewed from the gas cylinder tube. The gas cylinder lock can be completely removed from the cylinder with a suitable drift or by prying under the head with the combination tool.

c. To assemble the forearm group, replace the forearm on the gas cylinder tube and insert the forearm screws, long and short. Spring the front swivel bracket over the gas cylinder tube, and replace the swivel link, inner and outer, and swivel, fastening these in place by means of the swivel screws. All screws should be drawn up tight. Screw the gas cylinder in the gas cylinder tube to its proper setting, and push in the gas cylinder lock so that its head engages the notch in the gas cylinder. The registration of gas port is indicated by the circle marking on the front of the cylinder. When on the small port the smallest circle is toward the barrel, and in this position the cylinder should be about one turn from the shoulder. Unscrew one-third of a turn successively to register the larger ports.

32. Barrel group.-a. The barrel should never be removed until replacement is necessary and then only in a properly equipped shop. Before removing the barrel, strip the receiver of the gas operating, firing, and trigger mechanism. Barrels can sometimes be unscrewed with the combination tool by engaging the spanner in the notch provided in the breech end of the barrel. A special barrel dismounting wrench for the Browning automatic rifle