AUTOMATIC RIFLE

CONTENTS

CHAPTER	DESCRIPTION	PARAGRAPH
I	Introduction	1 - 5
II	Disassembly and Assembly	6 - 9
III	Disassembling and Assembling of the Trigger Mechanism	10 - 12
IV	Disassembling and Assembling of the Bipod Assembly (A2 Rifle Only)	13 - 14
V	Miscellaneous Instruction with the Automatic Rifle	15 - 20
VI	Functioning of the Automatic Rifle	21 - 25
VII	Care and Cleaning of the Automatic Rifle	26 - 29
VIII	Stoppages and Immediate Action	30 - 34
IX	Preparatory Marksmanship Training	35 - 43
X	Range Practice	44 - 48

CHAPTER I



1. Development of the Automatic Rifle.

The Browning Automatic Rifle, Caliber .30, Ml918, was developcd during the World War to meet the need of the American Infantry for an automatic arm capable of being operated by one man and of accompanying the rifle squad in all phases of combat. The design of Mr. John M. Browning was selected as the best of twenty-six similar weapons which were presented for test.

This arm was manufactured in quantity and issued to American Infantry units, and it proved to be an excellent weapon, reliable, simple in operation, and sturdy in construction. A later model, the Browning Automatic Rifle, caliber .30, Ml918A2, was developed. It was equipped with a ligbt bipod and a shoulder rest for the purpose of increasing its stability and reducing its dispersion, but the most marked improvement was attained by incorporating in the operating mechanism a simple device which reduces the cyclic rate of the gun from nbout 550 to approximatdy 350 rounds per minute. When operating at tbis reduced cyclic rate, a decided decrease in dispersion is obtained, with greatly improved accuracy for automatic fire.

Units of the R. 0. T . C. will for some time: be equipped with the unmodified automatic rifle (Ml918). However with the exception of the added parts designed to reduce the cyclic rnte of the gun, there is no important difference in the internal mechanism of the modified ru1d unmodified automatic rifles.

2. Description.

a. Both models of the Browning Automatic Rifle are gas-operated, air-cooled, magazine-fed, shoulder weapons. Gas-operated means that the energy necessary to actuate the rifle is derived from the expanding powder gases resulting from the ignition of a cartridge. Actually, as will be shown later, the rifle is really a small, efficient gas engine which operates very much like an automobile engine. The ignition of a cartridge changes the powder in the cartridge case from a sol id to a gas, just as the spark from a spark plug chauges the mixture in the cylinder of an automobile eng~e from a vapor into a gas. While the gas, in the barrel of the automatic rifle, is driving tbe bullet out of the bore some of it escapes into a cylinder where it strikes a piston, driving it to the rear, exactly as is, done in a cylinder of any gas engine. After the gas has driven the piston to the rear, it is exhausted in the same manner that used gas is exhausted from any gas engine.

During the rearward movement of the piston the processes of unlocking the bolt, the extraction and ejection of the empty cartridge case, and the compression of the recoil spring, which furnishes energy to move the piston forward again , are effected. During the forward movement of the piston the feeding of another cartridge into the chambu locking the bolt, and igniting the cartridge are accomplished.

The automatic rifle, like any other weapon, gets hot when fired. It has no special cooling device, as does the Browning machine gun, which has the barrel immersed in water. The greater part of the surface of the barrel is merely exposed to the air; consequently, it is known as an air-cooled weapon. The hand of the firer is protected from the heat of the barrel by the large wooden forearm. Care must be taken to avoid touching the barrel during firing. T he ammunition is fed into the automatic rifle from a magazine, having a capacity of 20 rounds. Therefore it is classed as a magazine-fed weapon.


PLATE 1.


PLATE 1a.

b. Firepower.

(1) M1918. The unmodified or Ml918 model is capable of semiautomatic fire at the rate of 100 rounds per minute but its rate of effective sustained fire is about 40 rounds per minute.

(2) M1918A2. The modified or Ml918A2 model is not capable of semiautomatic fire. The.re ore two cyclic rntes of fo.11 automatic fire, norrnaJ and slow, which may be selected by the fi rer. The normal cyclic rate is upproximately 550 rounds per minute; the slow cyclic rate is approximately 350 rounds per minute. The diective rate of fire for this weapon .. is froin 120 to 150 rounds per minute.

3. Capabilities and Limitations.

a. The weight and bulk of the automatic rifle prohibit the use of the bayonet with it; therefore it acts by firepower alone. The weapon, like all weapons, has limitations; for example, it is not capable of sustained fire as long as the machine gun, nor is it suited for overhead or indirect fire.

b. The automatic rifle can be fired from all positions prescribed for the service rifle. The best position from which to fire the weupon is the prone with a rest. This position is similar to the prone position with the serv ice ri.Bc, except that the gas cylinder tube is permitted to re~t on some object such as a sandbag, stump, log, or pile of earth. The Ml918A2 rifle is equipped with a bipod, so that no rest is necessary. The sights are large as compared with the sights on the service rifle. Primarily, the weapon was designed to cover an area with a large volume of lire rather than for accurate shooting, such as sniping.

4. General Data.

The unmodified automatic rifle (Ml918), without magazine, weighs 15 pounds and 14 ounces. The modified (Ml918A2) rifle weighs about 21 pounds. The empty magazine weighs 7 ounces; when filled, it weighs 1 pound and 7 ounces and has a capacity of 20 rounds. The overall length of the weapon is 47 inches; the length of the barrel only 24 inches; and the distance of the gas port from the muzzle is 6 inches. The sights a.re graduated for cdcvations from 200 to 1600 yards. TI1ey are not adjustable for wind conditions. The ammunirion used is the same as for the service rifle.

5. Outline of Training.

A soldicr who is to be trained as an automatic rifleman should be taught the fondamentals of shooting first by undergoing a thorough course in marksmanship with the service rifle. Then, in order properly to train the individual to be capable of getting the most out of the automatic rifle, he must be thoroughly instructed in the following subjects:

a, Mechanical training.
b. Marksmaship, known distance targets.
c. Marksmanship, moving ground targets.
d. Marksmanship, air targets.


Questions

1. How is the automatic rifle operated? Cooled? Fed?
2. What is meant by gas operated?
3. What processes are effected during the rearward movement of the piston?
4. What processes are effected during the forward movement of the piston?
5. Describe the cooling system of the automatic rifle.
6. What is the difference between the normal cyclic rate of fire and the more effective rate of fire for the Ml918A2 automatic rifle?
7. From what positions can the automatic rifle be fired? Wbat is the best position?
8. State the following relative to the automatic rifle (both models):
a. Weight.
b. Weight of the magazine empty and filled.
c. Overall length and distance of gas pon from the muzzle.
d. Type of ammunition used.
9. In what subjects should the automatic rifleman be instructed in order to get the most out of the weapon?



CHAPTER II

DISASSEMBLY AND ASSEMBLY

6. mechanical Training.

The purpose of mechanical training is to give the soldier such training as will insure his ability to maintain the continued successful mechanical operation of the weapon. This weapon is a gas engine, as well as a rifle, and the automatic rifleman should be able to 1ix it if anything goes wrong in combat. If he knows enough to make minor repairs, he can keep it in action. It is practically worthless to him if he cannot make it shoot. Mechanical training will be taken up as soon as practicable after the soldier receives his rifle. In any case it will be completed before any fuing is done with the rifle. Instruction in care and cleaning of the rifle will also be given.

7. General Rules.

During the course in mechanical training the following general rules must be observed:

a. Nomenclature is not taught as a separate subject. The soldier should get in the habit of giving each part of the wciapon its proper name each time he handles it, and thw correct nomenclature will result. b. The automatic ri£1c is des'igned for disassembling and assembling without force. If force is required it is an indication that an error has been made and further application of force will result in damage to the ri£1c. c. The weapon will not be disassembled or assembled against time. This results only in unnecessary damage to the parts. By thorough training the soldier habitually lays the parts out in their rroper sequence on a smooth, clean surface as they are removed from the rifle and disassembling and assembling become second nature. d. When the soldier has become adept in field disassembling and assembling, he may practice the operations blindfolded, simulating darkness. e. The forearm, barrel, butt stock and buffer, rear sight, and receiver groups arc not disassembled or assembled by the individual soldier.

8. Disassembling.

a. Sequence. The disassembly of the rifle authorized to be performed by the individual soldier without supervision is performed in the fallowing sequence:

(1) Remove flash hider.
(2) Remove biped assembly. Ml918A2 only.
(3) Remove flash hider spring lock washer.
(4) Cock the rifle.
(5) Remove the gas cylinder tube retaining pin.
(6) Remove the gas cylinder tube and forearm assembly.
(7) Let the mechanism forward easily and remo...e the trigger guard retaining pin.
(8) Remove the trigger guard.
(9) Remove the recoil spring and recoil spring guide.
(1O) Push the hammer pin part way through the hammer pin hole in the recciTcr.
(11) Remove the operating handle.
(12) Remove the hammer pin.
(13) Remove the hammer.
(14) Remove the slide.
(15) Push out on the bolt guide.
(16) Remove the bolt, bolt lock, and bolt link.
(17) Remove the firing pin.
(18) Remove the bolt link pin and the bolt link.
(19) Remove the extractor and spring.


h. Method and detailed explanation. (See Plate 2).

9. Assembling.

a. Sequence.

Assembling is in reverse order of disassembling. The steps are performed in the following sequence:

(I) Replace the extractor and spring.
(2) Replace the bolt link and bolt link pin.
(3) Replace the firing pin.



PLATE 2a.


PLATE 2b.


PLATE 2c.


PLATE 2d.


PLATE 2e.

(4) Replace the bolt, bolt lock, and bolt lock pin.
(5) Replace the slide.
(6) Replace the hammer.
(7) Insert the hammer pin (only far enough to register all holes).
(8) Replace the operating handle.
(9) Fully scat the hammer pin.
(10) Replace the recoil spring and guide.
(11) Replace the trigger guard.
(12) Replace the trigger guard retaining pin.
(13) Cock the piece.
(14) Replace the gas cylinder tube and forearm.
(15) Replace the gas cylinder tube retaining pin.
(16) Let the slide forward easily.
(17) Replace flash hider spring lock washer on muzzle.



PLATE 3a.


PLATE 3b.


PLATE 3c.


PLATE 3d.


PLATE 3e.

(18) Replace bipod assembly on flash hider (Ml918A2 only rifle) and screw flash hider onto muzzle.
(19) Test rifle by pulling trigger.

b. Method and detailed explanation. (Sec Plate 3).

Questions

1. What is the purpose of mechanical training?
2. How docs the student learn the correct nomenclature of the automatic rifle?
3. Why should force not be used in disassembling the automatic rifle?
4. Is the automatic disassembled and assembled against time? Blindfolded?
5. Give the sequence of disassembling.
6. In what position is the rifle placed on the table for disassembling and assembling?
7. Expfain how to remove the hammer pin.
8. Explain how to remove the bolt from the receiver.
9. Give the sequence of assembling.
10. What holes must be lined up to insert the hammer pin?


CHAPTER III

DISASSEMBLING AND ASSEMBLING OF THE TRIGGER MECHANISM

10. General.

The trigger mechanism is remarkably sturdy. Breakages in it are very rare, It need not be disassembled each time the weapon is cleaned and therefore field disassembling of the rifle does not include the trigger mechanism. The trigger mechanism is not disassembled and assembled blindfolded, simulating darkness.

11. Disassembling of Trigger Mechanism.

a. Sequence.

The trigger mechanism is disassembled in the following sequence:

(1) Remove the ejector.
(2) Remove the magazine catch spring.
(3) Remove the magazine catch pin.


PLATE 4a.


PLATE 4b.

(4) Remove the magazine catch.
(5) Remove the magazine release.
(6) Remove the sear spring.
(7) Remove the trigger pin.
(8) Remove the trigger and connector.
(9) Remove the scar pin.
(10) Remove the sear and sear release stop lever.
(11)Remove the sear carrier and counterrecoil spring.
(12) Remove the change lever spring.
(13) Remove the change lever.


b. Method and detailed explanation. (See Plate 4).


PLATE 5a.


PLATE 5b.


PLATE 5c.

12. Assembling Trigger Mechanism.

a. Sequence.
The steps in assembling arc in the reverse order of the disassembling. They are performed in the following sequence:

(1) Replace the change lever.
(2) Replace change lever spring.
(3) Replace counte.rrecoil spring and scar carrier.
(4) Insert scar pin part way and replace sear.
(5) Fully seat scar pin.
(6) Replace trigger.
(7) Insert trigger pin.
(8) Replace connector.
(9) Replace sear spring.
(10) Replace magazine release.
(11) Replace magazine catch.
(12) Replace magazine catch pin.
(13) Replace magazine catch spring.
(14) Replace ejector.


b. Method and detailed explanation. (See Plate 5).

Questions

1. Is it necessary to disassemble the trigger mechanism each time the rifle is cleaned
2. Is the trigger mechanism disassembled and assembled blindfolded?
3. Give the sequence of disassembling the trigger mechanism.
4. Explain how to remove the ejector.
5. In disassembling is the trigger pin removed before the sear pin?
6. Explain how to remove the sear pin.
7. Explain how to remove tbe change lever spring.
8. Give the sequence of assembling the trigger mechanism.
9. Explain how the connector is replaced in assembling the trigger mechanism.
10. Which side of the magazine catch is to the front when it is assembled?




CHAPTER IV

DISASSEMBLING AND ASSEMBLING OF THE BIPOD ASSEMBLY (M1918A2 RIFLES ONLY)


PLATE 6.

13. Disassembling of Bipod.

The bipod assembly is disassembled in the following sequence ( See Plate 6):

(1) Remove the two bipod leg clamp wing screws.
(2) Remove the right and left bipod leg assemblies.
(3) Remove the two bi pod clamp leg guides.
(4) Remove the two bi pod body wing screws.
(5) Remove the right and left bipod leg tubes.


14. Assembling of the Bipod Assembly.

The bipod assembly is assembled in the following sequence:

(1) Replace bi pod leg tubes in bi pod body so that unthreaded holes of. bi pod leg clamps are facing outward.
(2) Replace two bipod body wing screws.
(3) Replace the two bipod clamp leg guides m their slots on the right and left bipod legs.
(4) Replace bi pod leg assemblies in bi pod leg tubes.
(5) Linc up U-shaped opening of bipod clamp leg guides with holes in bipod leg clamps.
(6) Replace bipod leg clamp wing screws.



CHAPTER V

MISCELLANEOUS INSTRUCTION WITH THE AUTOMATIC RIFLE

15. The Magazine. a. Sequence of dissassembling and assembling.

(1) Remove the magazine base by raising the rear end until the indentations thereon are clear, and sliding the base to the rear. The magazine follower and spring will then fall out.

(2) The magazine is assembled in reverse order. It should be noted that the bent end of the follower and the eye of the spring work against the inside of the rear (notched) end of the magazine.

b. Method of operating the magazine.
To fill the magazine, place the wide end of the magazine filler over the top of the magazine so that the groove in the filler fits over the catch rib of the magazine. Hold the magazine in the same relative position that it occupies in the rifle; that is, with the catch rib toward the operator. Insert a clip of cartridges in the guides provided in the filler, and with the right thumb near the base force the cartridges into the magazine. Each magazine will hold four clips.

(2) To insert the magazine. Press the magazine release and withdraw the empty magazine. Hold the loaded magazine with the base in the palm of the right hand, cartridges to the front. Insert the magazine between the sides of the receiver in front of the trigger guard, and push it home with the right hand. The magazine can be inserted with the mechanism in either the cocked or forward position. It is ordinarily inserted, however, after the rifle has been cocked.

16. To Set the Change Lever Control. The change lever controls the rate of fire.

a. M1918. (1) For semiautomatic fire, or single shot, push the change lever to the forward position, marked F.

(2) For full automatic fire or continuous fire to the capacity of the magazine, set the change lever in the vertical position against the change lever stop, marked 4.

(3) To set the rifle at "safe," depress the change lever stop and pull the change lever rearward until it covers the change lever stop. This position is marked S. The change stop prevents the accidental setting of the change lever at safe, and at the same time allows a quick change from safe to either full automatic or semiautomatic fire.

b. Ml918A2. (1) For the slow cyclic rate of automatic fire or single shot, push the change lever to the forward position marked "F."

(2) For the normal rate of automatie fire, set the change lever in the vertical position against the change lever stop, marked "A."

(3) To set the rifle at safe, depress the change lever stop and pull the change lever rearward until it covers the change lever stop. This posit1on is marked "S." The change stop prevents the accidental setting of the change lever at safe, and at the same time allows a quick change from safe to either full automatic or semiautomatic fire.


PLATE 7.


PLATE 8.

17. Spare Parts and Accessories.

a. General.

The accessory and spare-parts case, Ml918, contains the parts and tools to remedy all temporary stoppages. Without them the rifle is liable to be out of action indefinitely; with them the rifle can be returned to action in a few seconds. The importance of knowing what is, and what is not, carried as a spare part should be impressed on all automatic riflemen. It is essential that they know where to find any spare part that may be required.

All spare parts must be given their proper names; the use of other names is forbidden. A list of deficiencies in the spare parts kit should be kept inside each gun box, Spare parts must be kept lightly oiled, and breakages and losses must be reported immediately. Worn or defective parts should not be kept in the accessory and spare parts case. Care should be taken to sec that automatic rifles kept in reserve are in the same condition of readiness for action as those to be used on the firing line. They should not be utilized as a source for obtaining spare parts.


PLATE 9a.

b. Accessory and spare parts case, M 1918, and fabric envelope.
The accessory and spare parts case should be given the same care as other leather equipment. The contents should always be properly packed. The small fabric envelope is used to hold the recoil spring after it has been coiled up. The remaining spare parts are packed in the large fabric envelope. The accessory and spare-parts case, M-1918, contains:

1 Brush and thong, assembly.
1 Connector.
1 Envelope, fabric, large.
1 Envelope, fabric, small.
1 Extractor.
1 Extractor, ruptured cartridge, Mk. II.
1 Oiler, oval, 3-ounce, with cap and chain.
2 Pins, firing.
1 Pin, magazine catch.
1 Pin, retaining, gas cylinder tube, assembly.
1 Pin, retaining, trigger guard, assembly.
1 Spring, extractor.
1 Spring, magazine catch.
1 Spring, recoil.
1 Spring, sear.
1 Stop, change lever, assembly.
1 Tool, cleaning, gas cylinder.
1 Tool, combination.


c. Ruptured cartridge extractor, Mk. II. When a cartridge ruptures the front end is left in the chamber. This fragment of the case telescopes over the bullet end of the next cartridge which is fed into the chamber. As vie operating handle is pulled back the live cartridge is extracted and ejected, sometimes withdrawing the ruptured fragment with it. In this case the use of tbe ruptured cartridge cxtractor 1s unnecessary.


PLATE 9b.


PLATE 9c.


PLATE 9d.


PLATE 9e.

If the ruptured end is not extracted by the following cartridge, cock the rifle and remove the magazine. Insert the ruptured cartridge extractor through the ejection opening and push it forward into the chamber. Let the bolt forward without excessive shock so. that the extractr engages, the rim of the ruptured cartridge extractor. Dcaw the operating lundle back, extracting and ejecting the ruptured cartridge extractor and the ruptured fragment of the cartridge case. To remove this fragment from the ruptured cartridge extractor, unscrew aad remove the spindle and sleeve from the head of the ruptured cartridge extractor.

d. Combination tool.
The small spanner at the head of the combination tool is used to turn the gas cylinder or the flash hider. Barrels, which arc not excessively tight in the receiver, can be removed and replaced by the use of the larger spanner, although shop facilities arc necessary for the proper accomplishment of this work, and it should not be attcmpc.cd by line troops.

e. Gas cylinder cl~aning tool.
The gas cylinder cleaning tool is provided for the cleaning of the gas operating mechanism. Using the tool as a hand reamer, insert the smooth end of the body into the cylinder, turning it to the right as it is advanced toward the cylinder bead. As soon as it reaches the head, press down and give the tool a few turns to cut the carbon from the inside surface of the head, Withdraw and reverse the tool, using the recess cutter as a gauge to remove the carbon from the recess at the forward end of the interior of the gas cylinder. This part should be thoroughly cleaned, especially that portion near the edge of the operating surface of the cylinder wall. Using the drift point, clean the ports in the barrel, gas cylinder tube and gas cylinder. Scrape the carbon from the face of the piston with the front cutting edge of the cleaning tool body, and remove the deposit from between the piston rings with the drift point.

18. To Change the Firing Pin Without Disassembling. (See Plate 9.)

To remove the firing pin, lay the rifle on the table, barrel down, muzzle to the front. Remove the trigger mechanism. Place the rim of a cartridge under the center of the bolt guide. Hold base of cartridge firmly up under bolt guide with right forefinger (Fig. 1, "Plate 9). Pllll operating handle all the way to rear with the left forefin~er. Press down on the nose of the cartridge with the right thumb to free the bolt (Fig. 2, Plate 9). Push down on the bolt Link with the second finger of the left hand (Pig. 3, Plate 9), causing the bolt to break at the bolt lock pin (Fig. 4, Plate 9). Allow the mechanism to go forward until it stops. Change the fuing pin. Pull the operating handle to rear agai.11, and push the bolt into position (Fig. 5 Plate 9).

19. To Change the Extractor Without Disassembling.

Draw back the mechanism and insert an empty cartridge case between the bolt and chamber so that the extractor is opposite the ejection opening. With the forefinger of the left hand force out the claw of the extractor, then place the point of a cartridge behind the extractor shoulder and pry forward until the extractor is free of the recess. Remove the extractor spring. To assemble: the extractor insert the short end of the extractor spring in the hole in the shank of the extractor, having the long end of the spring along the slot in the extractor. Insert the extractor and spring in the end of the bolt and push into position.

20. Gas Adjustment.

a. There are three ports of different sizes which permit gas to enter the gas cylinder. The positions of these ports through the wall of the gas cylinder are indicated by three circles marked on the head of tl:ie gas cylinder. The ri8e should normally be operated on the smallest port, and this setting will not be varied unless the: rifle shows signs of insufficient gas. To align the smallest port, screw in the gas cylinder with the combination tool until the shoulder of the gas cylinder is about one turn from the corresponding shoulder of the gas cylinder tube and the smallest circle on the cylinder head is toward the barrel. Lock the cylinder in position by seating the ga.s cyl indcr lock in the recess in the gas cylinder tube. If, upon £ring, the rifle shows signs of insufficient gas, try setting the cylinder one complete turn on each side of the original setting. As soon as the proper setting has been obtained the rifleman will carefully note the position so that he can quickly assemble the cylinder to the proper point without trial.

b. The larger ports are provided for. uso in case of emergency, when the action of the rifle has been made sluggish through the collection of dirt and grit, or the lack of oil, and conditions render it impossible for the rifleman to correct these troubles. For this reason the threads should be kept clean and oiled and the cylinder free to turn if necessary, Under adverse conditions, and when signs of insufficient gas become apparent, the cylinder should be unlocked and unscrewed one-third of a turn, thus registering the medium circle and alining the medium port with the gas orifice; and then be locked in that position. To unlock the gas cylinder, push in on one side of the split pin which is opposite the gas cylinder lock. This will force the lock out of the recess in the gas cylinder tube. Repeat this operation in order to connect the largest port with the barrel.

c. Results of insufficient gas.

(1) Failure to recoil ( usually due to a misaligned or excessively clogged gas port, or extremely dirty mechanism).
(2) Failure to eject.
(3) Weak ejection.
(4) Uncontrolled automatic fire (exceptional).

d. Results of too much gas.

(1) Excessive speed, causing pounding.
(2) Excessive heat in gas operating mechanism.


QUESTIONS

1. Explain the disassembling of the magazine.
2. Explain how the magazine is filled.
3. What is the purpose of the change lever?
4. Explain how to set the change lever on safe.
5, Name ten parts carried in the spare parts kit.
6. Explain how to use the ruptured cartridge extractor.
7. What are the uses of the gas cylinder cleaning tool?
8. Explain how to change the firing pin without disasscm ing the piece.
9. Explain how to change the extractor without disassemblfr1g the piece.
10. Explain how to set the gas cylinder on the smallest port; the medium port.


CHAPTER VI

FUNCTIONING OF THE AUTOMATIC RIFLE

21. General.

a. After a round has been fired in a Springfield rifle the rifleman must perform several operations in order to fire a second round. He must raise the bolt handle in order to unlock the bolt; draw the bolt to the rear extracting the empty case from the chamber and ejecting it from the rifle; shove the bolt forward feeding a live round into the chamber; turn the bolt handle down locking the bolt and finally press the trigger igniting the cartridge. On any automatic weapon all these operations must be performed by the weapon itself. In the automatic rifle some of the gas resulting from the explosion of a cartridge is diverted from the batrd and conducted to a cylinder where it strikes the piston, driving it to the rear; and then by means of various springs, cams,plugs the rifle performs the operations necessary to continue fuing.

b. A lug is a projection against which another part operates or bears. The lug on the firing pin is an example. A cam (or beveled) surface is one that slides on some other surface. To cam is to cause motion of a part by means of a sliding contact between two surfaces.

c. The various operations performed by the mechanism have a certain sequence. Some of them are concurrent.

d. For convenience, the functioning of the automatic rifle is divided foto two phases based on the operation of the mechanism when a shot is fired. They are the first phase, covering the backward movement of the parts; and the second phase, covering the forward movement of the parts. The ignition of a cartridge in the c·hamber is taken as the starting point.

22. Description of First Phase.

(For detailed description see FM 23-15 or FM 23-20)

a. A cartridge having been ignited, the bullet, under the action of the expanding powder gases, travels through the barrel, and when it reaches a point near the end of the muzzle passes over a port in the bottom of the barrel.

b. The gas expands through the port in the bottom of the barrel into a well in the gas cylinder and acts upon the head of the piston, driving it to the rear.


PLATE 10 and PLATE 11.
Figure 10. Shows expanding gases passing through gas port inot gas cylinder. Gas strikes piston plug with hammer like blow driving piston with slide to the rear.
Figure 11. Showa action of gas, movement of piston to the rear and gas escaping through six port holes in the tube.


PLATE 12.

c. As the piston is forced bnck it carries with it the slide, to which it is attached, causing the compression of the recoil spring.

d. The slide, as it first moves rearward, imparts no motion to the bolt lock, thereby allowing the high pressure in the bore to be decreased before unlocking begins.

e. The slide continues its movement to the rear, causing the link to pull the bolt lock down and away from the locking recess in the top of the receiver.

f. As the bolt lock is pulled down a cam surface on its underside comes in contact with a lug on the firing pin, camming the firing pin away from the face of the bolt, and keeping it securdy locked away [rom the face of the bolt at all times when the mechanism is not locked in its forward position. After the bolt lock has been pulled down from out of the locking recess the bolt is pulled to the rear, carrying with it the empty cartridge case which is being slowly extracted from the chamber and which is held on the face of the bolt by the extractor.

g. Shortly before the mechanism reaches its rearward position the base of the cartridge strikes the ejector, causing the empty cartridge case to be pivoted about the extractor and through the ejection opening.

h. The rearward movement is terminated when the slide strikes the buffer which takes up practically all shock of recoil and decreases the cyclic rate of the gun from 1200 shots a minute to 600.

23. Description of Second Phase.

(For detailed explanation see FM 23-15 or FM 23-20.)


PLATE 13.


PLATE 14.


PLATE 15.

a. If the sear nose is depressed the mechanism will go forward under the action of the recoil spring. If the sear nose is not depressed the sear notch on the slide will engage the scar nose and the trigger must then be pulled before the mechanism will move forward.

b. As the mechanism moves forward under the action of the recoil spring, the feed rib on the bolt strikes the base of the top cartridge in the magazine, carrying it forward and seating it in the chamber.

c. During the forward movement of the mechanism the bolt lock is cammed upward (see Plate 14), until it is seated in the locking recess locking the bolt in its forward position.


PLATE 16.

This upward movement of the bolt lock releases th.c firing pin, permitting the hammer, as it continues forward, to strike the firing pin and thus ignite the cartridge. (Sec Plate 13.)

d. The forward movement of the mechanism is terminated by the forward end of the slide striking a shoulder at the rear end of the gas cylinder tube.


PLATE 17.

24. Functioning of the Trigger Mechanism.

a. M1918.

(1) By changes in the operation of the trigger mechanism the unmodified automatic rifle can be set on safe, fired automatically or semi-automatically. These changes are made by moving the change lever to the various positions marked S, A, cir F on the receiver.

(2) The forward end of the sear is held down by the sear spring at all times, unless a force is exerted to oppose it. Pressure on the trigger forces its rear end up and, as it rises, it lifts the connector which, in turn, raises the forward end of the sear against the action of the sear spring. This is how pressure on the trigger is transmitted to the sear.

(3) The shank of the change lever is a cylindrical bar with a solid portion, a cutaway portion, and another cutaway portion containing a tongue: of metal. The functioning of the trigger mechanism is governed by whichever portion 0f the shank of the change lever is nearest the rear shoulders of the trigger.

(4) Safe. When the change lever is turned to S the solid portion of the shank simply blocks any upward movement of the rear shoulders of the trigger when pressure is applied and the sear spring is not opposed. The sear nose therefore cannot be depressed.


PLATE 18.

(5) Automatic. When the change lever is set on A the cutaway portion of the shank containing the small tongue of metal is nearest the rear shoulders of the trigger. Pressure on the trigger causes its rear end to rise up into the cutaway portion of the shank of the change lever until the tongue of metal contacts the toe of the connector.


PLATE 19. This figure shows the functioning of the trigger mechanism for the M1918 rifle. Set for single shot firing. The connector cammed forward from end of sear to return to position under action of sear spring, causing rear end of sear to engage in sear noth in slide.


PLATE 20.


PLATE 21.


PLATE 22.

This upward movement of the trigger is sufficient to permit the connector to raise the forward end of the sear against the action of the sear spring. In this way the sear nose is depressed so that it cannot engage the slide and the rifle will fire and continue to fire until the pressure is released.


PLATE 23.

(6) Semi-automatic. When the change lever is set on F the cutaway portion of the change lever shank is nearest the rear end of the trigger and the tongue of metal on the change lever shank is rotated out of the path of connector. Pressure on the trigger raises its rear end, carrying the connector up with it. This front end of the sear is raised against the action of the sear spring depressing the nose thus releasing the slide. In this case the rise of the connector is not limited by the tongue of metal on the change lever shank, and it does rise to a point where a cam surface on its rear side makes contact with a cam surface on the sear carrier.· Further pressure on the


PLATE 24.

trigger causes the top of the connector to be cammed forward out from under the sear. This permits the sear spring to lower the forward end of the sear, raising its nose in time to again engage the slide so that only one shot is fired. The center leaf of the sear spring returns the connector and trigger to their original positions when pressure on the trigger is released.

b. M1918A2.

(1) Normal cyclic rate (A).
This is the same as "automatic" described for the unmodified rifle M1918.

(2) Slow cyclic rate (F).
When the change lever of the Ml918A2 rifle is set at (F) the sear is depressed, thereby disengaging the sear and sear notch when the trigger is pulled, but the mechanism is so constructed that the sear rises and engages in the sear notch when the slide comes back again, and the sear notch will not disengage until the sear release in the buffer (see Plate 24c) depresses the rear end of the sear by riding over the cammed end of the sear, or the trigger is fully released and then pulled. With this setting, the riAe fires one shot for each pull and quick release of the trigger, or a slow cyclic rate of 350 rounds per minute for the length of time the trigger is held completely to the rear. (For detailed description see Par. 23, FM 23-15 or FM 23-20.) (3) Safe (S). When so set, the sear cannot be released from the sear notch by pulling the trigger.

25. Functioning of the Combination Buffer and Rate Reducing Mechanism, M1918A2 Rifle.

a. Parts. The buffer and rate reducing mechanism of the modified (Ml918A2) rifle consists of the following parts, which are assembled in the order given, from front to rear. (See Plate 24b.)

(1) The buffer tube, which has four splined slots on the inside of the forward end for use in positioning the buffer head. One of these slots is used to anchor the buffer tube to the buffer head by means of the buffer key.

(2) The buffer head.

(3) The sear release, inserted in the bufier head,

(4) The buffer key, which holds Lhe sear release in the buffer head and anchors the buffer tube to the buffer head.

(5) Four bn1ss friction cups, with concave interiors which are split to allow for expansion.


PLATE 24b.

(6) Four steel cones, to fit into the brass friction cups. Cups and cones are placed one after the other in series.

(7) The buffer spring.

(8) The actuator.

(9) The buffer tube cap.

(10) The actuator tube.

(11) The actuator spring (inside actuator tube).

(12) The stotk retaining sleeve lock washer.

(13) Stock retaining sleeve.

(14) Actuator stop.

(15) Fin.

b. Action.

(1) When the automatic rifle is fired at the slow cyclic rate, the buffer head and sear release, struck by the rear end of the slide, move to the rear. The buffer head forces the friction cups over the cones, causing them to expand tightly against the tube, consequently producing considerable friction as the cups move back and compress the buffer spring. Thus the rearward action of the slide is checked gradually and there is practically no rebound. The buffer spring returns the buffer head and friction cups and cones to their original positions.

After striking the buffer head and sear release, the slide moves forward until it is engaged by the sear. The delayed rele:rse of the sear is then accomplished as follows: The sear release when struck by the slide in turn strikes the actuator in the buffer. The actuator is driven to the rear inside the actuator tube against the actuator spring. It returns under the force of expansion of the actuator spring to drive the sear release forward against the cammjng surface on the rear of the sear, thus releasing the sear and permitting the rifle to continue its cycle.


PLATE 24c.

(2) When the change lever is set for the normal cyclic rate the scar release is prevented from engaging the camming su rface on the rear end of the sear by the scar release stop lever. Otherwise the functioning of the mechanism is the same as described in (1).

Questions

1	What operations arc performed mechanically by the automatic rifle that the firer must perform in firing the Springfield rifle?
2	What is a lug? A cam surface?
3	How docs gas get from the bore to the cylinder?
4	What causes the compression of the recoil spring?
5	Explain how the lock is pulled down out of its recess.
6	Explain how the firing pin is cammed away from the face of the bolt.
7	Explain how the empty cartridge case is ejected from the rifle.
8	What functions arc performed by the bufier?
9	What furnishes the energy necessary to move the parts forward when the trigger is pressed?
10	Explain how a cartridge is seated in the chamber as the bolt goes forward.
11	Explain how the cartridge is ignited.
12	Explain how movement of the trigger is transmitted to the sear.
13	When the change lever is turned to S what portion of the shank of the change lever is nearest the rear shoulders of the trigger?
14	Explain how the setting of the change lever on A causes the unmodified rifle (Ml918) to fire automatically.
15	Explain how the setting of the change lever on F causes the unmodified rifle (Ml918) to fire semi-automatically.
16	Is the modified (M19I8A2) rifle capable of semi-automatic fire?

CHAPTER VII

CARE AND CLEANING OF THE AUTOMATIC RIFLE

26. Importance. perform in firing the Springfield rifle.

a. General.
The care and cleaning of the automatic rifle cannot be overemphasized. The kind of attention given the rifle determines largely whether it will shoot accurately and function correctly. It is not only a firearm for the accurate propelling of bullets, but it is dso a small and very efficient gas engine. The bore and chamber must be in perfect condition for accurate shooting, and the gas system and operating mechanism must be in perfect condition for efficient functioning. Soldiers accustomed to the use of the service rifle are liable to think the job completed with the cleaning of the bore, but it must be realized that the mechanism of the automatic rifle requires the same care that should be devoted to any fine piece of machinery, It must be borne in mind that the action of primer and powder fouling extends to all parts with which the gas comes in contact; the bore, chamber, piston, gas cylinder, gas cylinder tube and the included gas ports. The statement has been made frequently that the automatic rifle is not dependable, but, during twenty years of experience with the weapon, it has been proven conclusively that where the weapon receives proper care and cleaning it is seldom out of action.

b. Lubrication.
Proper oiling is second in importance only to intelligent cleaning. It is a vital necessity for the working parts, but the oil should be used sparingly; wiping with a well-oiled rag is the best method. Oil all bearing surfaces of the rifle before firing.

c. Cleaning.
To clean the automatic rifle, swab the bore with an oily flannel patch. Repeat with dry patches until several successive patches come out clean. Push a patch dampened with oil through the bore to protect its surface. Dust out all screw heads and crevices with a small cleaning brush or small stick. Wipe all metal surfaces with a dry cloth to remove moisture, perspiration, and dirt. Wipe the outer surfaces of the automatic rifle, including the forearm, with a lightly oiled cloth, then clean with a soft dry one. Immediately after cleaning, wipe all the metal parts with a lightly oiled cloth. This protective film on all metal parts will be maintained at all times. At least once a month, and always after the stock and forearm have become wet, they should be rubbed thoroughly with a little linseed oil in the palm of the hand. Rub oil in until dry. Use only castile soap or saddle soap for cleaning or softening the sling.

27. Method of Cleaning After Firing.

a. First disassemble the rifle as in field disassembling and in addition remove the gas cylinder from the gas cylinder tube so that all traces of powder and primer fouling and all dirt and grit can be removed from all parts of the rifle.

b. Cleaning the bore.
(1) The firing of a cartridge leaves in the bore an ash from the burned powder and a salt (potassium chloride) from the primer of the cartridge. The powder ash is practically harmless but the salt, if left in the bore, absorbs moisture from the air and causes rust. This salt is easily dissolved by water. It is not soluble in oil. Therefore, clean the bore by swabbing it thoroughly with flannel patches saturated with hot sal soda solution or hot soapy water. Use hot water or cold water in that order of preference. Use a barrack cleaning rod with a slotted end and clean from the muzzle, being careful not to wear or rub unnecessarily the muzzle end of the bore. If available, a wet bronze or wire brush should be run through the bore several times to assist in loosening the fouling so that it can be swabbed out more easily with the saturated flannel patches.

(2) Then dry the cleaning rod and run dry patches through the bore until they come out dry and clean. Finally nm an oily patch through tHe bore, leaving it covered with a thin film of lubricating oiL (Note. The new type of ammunition now issued has eliminated metal fouling.)

c. Cleaning the chamber.
During firing, a certain amount of dirt and oil accumulates in the chamber where it is formed into a hard coating, akin to carbon. This coatinj! is easily removed with the automatic rifle cleaning brush while the chamber is hot, but is difficult to remove after it h:irdens upon cool mg. lf not removed, it causes the cartridge to stick in the chamber, resulting in failure to extract. Tbe automatic riBeman should be trained to use the cleaning brush immediately upon any cessation of firing, even if thi1 cessation is only for a few minutes. The deaning brush is introduced through the ejection opening in the receiver, and should be used vigorously, Upon completion of firing, the chamber is further deaned in the process of cleaning the bore, care being taken that water does not remain in the chamber, that the chamber is wiped dry with a patch wrapped around the forward portion of the cleaning brush, and finally lightly oiled in the same manner.

d. Cleaning the gas system.
The gas system, consisting of the gas cylindor, gas cylinder tube, piston and included gas ports, is subjected to powder and primer fouling to the same extent as the bore, and also receives carbon· deposits from the burning of oil. Insert the smooth end of the body of the gas-cylinder tool into the gas cylinder. As it is advanced toward the cylinder head turn it to the right. As it reaches the head, apply additional pressure to the tool and give it a few turns to cut the carbon from the inside surface of the piston head. Withdraw and reverse the tool. Using the recess cutter as a gage, remove the carbon from the recesses at the forward end of the interior of the gas cylinder. With the drift point, clean the gas ports in the barrel, gas cylinder tube, and gas cylinder. Scrape the carbon from the face of the piston with the front cutting edge of the tool body and remove the deposit from between the piston rings with the drift point. Wash with hot water and soap or sal-soda solution (if not available, use plain water), dry thoroughly, and oil lightly.

e. Cleaning the remainder of the rifle.
The breech mechanism, consisting of the receiver and all parts contained therein, and all exterior parts should be wiped with an oily rag to remove dirt and grit and then covered with a light film of oil for protection from rust.

f. Magazines should receive the same attention given other parts of the automatic rifle. Most failures to feed are due to faulty magazines which generally result from improper cleaning or rough handling.

28. Additional Rules for Care of Rifle.

a. Preparatory to firing.

(1) Remove the protective film of oil from bore and chamber.

(2) Work slide back and forth several times to see that it moves freely.

(3) Verify proper setting of gas port.

(4) Test trigger mechanism at "safe" (S), semiautomatic (F), and automatic (A) for the Ml918 model and at "Safe" for the Ml918A2.

(5) Examine magazines. It is imperative that magazines be given the best of care and kept in perfect condition. They should be disassembled, wiped clean and dry, and thinly coated with oil. Much dirt gets into them through careless handling on the ground during range or other firing. They must be kept free from dirt and rust which hinder their operation by making the spring and follower stick. Care must be exercised in the handling of magazines to avoid denting or bending them. The greatest possible care should be taken to prevent any damage to the lips of the magazine or to the notch for the magazine catch.

b. During firing.

(1) Keep bore free from dust, dirt, mud, or snow.

(2) Keep chamber free from oil or dirt.

(3) Keep moving parts oiled.

(4) Clean bore and gas system as frequently as opportunity during cessation of fire permits. The neglect of this precaution is a frequent cause of stoppages.

(5) Clean chamber frequently while still hot wiLh chamber brush by inserting it through the ejection ope.ning in the receiver.

c. After firing.

(1) The bore of the riAe will be 1horougbly cleaned, as described in par. 27, by the eve11ing of the day on which it is fired, and similarly cleaned for the next 3 days.

29. Care and Cleaning of the Automatic Rifle in the Field.

a. Conditions of service in the field increase the probabilitv of the rifle becoming dirty as well as the difficulties of proper cleaning. However. the rifle must receive the best care possihle under the conditions. If no cleaning rod is available the thong and brush, carried in the spare-parts case, will be used. Special attention must be paid to 1he prevention of rust. The weapon will be cleaned as described in paragraphs 27 and 28, depending upon whether or not it has been fired.

b. In advancing, after having opened fire, it is advisable to let the bolt go forward on an empty chamber before each advance, in order to keep dirt from getting in the receiver, chamber or magazine. This is done by lowering the magazine, pressing the trigger allowing the bolt to go forward, and then pushing the magazine in place.

QUESTIONS

1. What parts of the automatic rifle are subject to primer and powder fouling?

2. To what extent must the automatic rille be disassembled for cleaning after firing?

3. Explain how to clean the bore ol the automatic rifle after firing.

i. Explain the use of the chamber cleaning brush.

5. Explain the cleaning of the breech mechanism.

6. What parts constitute the gas sy stem?

7. How is the gas systein cleaned? What is one objection to excessive oil?

8. What care is given to magazines?

9. Explain the care a1,1d cleanwg of the automatic rifle in garrison.

10. Explain how to clean the aUlomatic rifle in the field.


CHAPTER VIII

STOPPAGES AND IMMEDIATE ACTION

30. Stoppages.

a. A stoppage is a failure of the mechanism to function.

b. Stoppages are classed as prolonged or temporary. A prolonged stoppage is one which cannot be remedied in the field under fire, such as the failure of some part which cannot be replaced or which requires special shop facilities. A temporary stoppage is one which the automatic rifleman can correct in the field. This type of stoppage results from the failure of a part which can be replaced from the spare parts kit; from faulty ammunition; and from improper care and cleaning.

c. The automatic rifleman should understand the causes of and the remedies for temporary stoppages in order to get the best possible performance out of the weapon. This chapter deals only with temporary stoppages.

d. Causes of stoppages.

(l) Dirt. Natural fouling incident to firing and also to careless cleaning.

(2) Insufficient oil. From failure to oil and because of oil burning up during firing.

(3) Extraneous matter in working parts. Due to poor cleaning, brass chipped from cartridges, breakages, blown primers, and similar causes.

(4) lmproper assembly of the rifle. Gas ports not registered, middle prong of sear spring riding on one wall of the sear carrier, and similar causes.

(5) Breakages. Due to wrong assembly, oversize or undersize parts, burrs, incorrect heat treatment and the overheating of parts incident to firing.

(6) Burred parts. Due to improper assembly or use of force, dirt, grit, and foreign matter in the mechanism.

(7) Magazine troubles. Due to bent or dented magazines, worn magazine catch notch, foreign matter (such as blown primer) between the lips of the magazine and the top cartridge.

(8) Faulty ammunition. Defective primers or dented cartridges.

(9) Excessive play in parts. Due to wear in disassembling parts not supposed to be disassembled, such as removing the barrel from the receiver.

(10) Ruptured cartridges. Due to excessive head space. Headspace is the distance between the face of the bolt and the shoulder of a standard steel-test cartridge. If excessive headspace exists when the cartridge is chambered properly, the cartridge case will be forced against the walls of the chamber at the instant of explosion. The cartridge case base will be driven to the rear, as it is not supported hy the bolt. This results in rupture about one-halt inch from the base of the cartridge. In effect, the action during the period of gas pressure within the cartridge case is the same as iF the chamber gripped all the surface uf the cartridge case except the part about one-half inch near the base. The pressure within the cartridge case being 50,000 pounds a square inch, the ungripped portion of the case is torn from the gripped part and forced back against the face of the bolt. The case is never pulled apart by the extractor.


PLATE 25a.


PLATE 25b.


PLATE 25c.

31. Classification of Stoppages by Positions.

a. In order to facilitate recognition of the cause of a stoppage and the application of the proper remedy, stoppages are placed in four groups or positions. This classification is dependent upon the position of the bolt when the stoppage occurs. For example, if a stoppage occurs when the bolt is in its extreme forward position we know that it could be caused by only a few of the many possible causes of all stoppages. The position of the bolt is determined by pulling the operating handle to the rear until it strikes 1he hammer pin.

b. The boundaries of the positions are (See Plate 25):

(1) First position, mechanism and opera1ing handle fully closed.

(2) Second position, the operating handle strikes the hammer pin anywhere from fully closed to a point where the operating handle plunger pin ride, over the raised shoulders on the ribs of the operating handle guiclcway.

(3) Third position, the operating handle strikes the hammer pin anywhere from the second poskion to a point directly over F of the change lever setting.

(4) Fourth position, the operating handle strikes the hammer pin anywhere between the third position and its rearmost position.

32. Explanation of the Causes of Stoppages.

a. First position.

(1)Failure to feed. Usually traceable to magazine trouble. An obstruction (wually a blown primer) between the lips of the magazine and the top cartridge prevents the new cartridge from being engaged by Lhe feed rib and causes the bolt to go home on an empty chamber. The same stoppage occurs when the magazine catch notch becomes so worn as to permit the magazine to drop down slightly and also when the magazine catch breaks, or when the magazine: is not pushed clear up in the magazine opening.

(2) Failure to fire. Repeated failure to fire is usually due to a broken or short firing pin. Frequently the beginner will mistake a misfire, due to an obstruction between the face of the bolt and the breech, for one due to a broken firing pin. He should remember that the latter is a first position stoppage and the former a second position stoppage. A misfire due to a broken tiring pin will not show any indentation on the primer. The second position stoppage almost invariably shows a slight indentation.

(3) Insufficient gas. A stoppage in the first position with an empty case in the chamber is due to insufficient gas, which in turn may be due to the gas ports not being properly registered or being partially clogged, or to excessive friction because of lack of oil and a dirty chamber.

b. Second position.

A failure to close will usually be caused by an obstruction lodging between the face of the bolt and the breech, thus holding the firing pin away from the primer. The primer will be slighlly dented. This stoppage is typical, When the piece stops in the second position always look for an obstruction either on the face of the bolt or in the breech recess where the bolt and receiver join; the most frequent obstruction is a blown primer, but often it is difficult to determine, as frequently it drops off as the bolt is drawn back. If the stoppage recurs, it is certain that an obstruction is in the rifle bctwce. n the face of the bolt and the breech or between the bolt lock and the receiver top plate.

c. Third position.

(1) Ruptured case.
This stoppage is due to excessive headspace. When the immense pressure following the 1gn1t1on of tl1e charge 1s taken up by the cartridge case the latter, not being properly supported by the bolt, will rupture about one-hnlf inch from the base. The short end at the base must then be extracted and the larger portion of the case will remain in the barrel. A temporary correction for such a stoppage is to clean and oil the chambcr thoroughly and oil the cartridges,

(2) Broken firing pin.
This stoppage is caused by the end of a broken firing pin protruding through the firing-pin hole 1n the face of the bolt. The cartndgc is then kept from sliding under the extractor as the bolt moves forward and a third potition stoppage will result. The cartridge will show an abrasion near the base. To remedy this stoppage the firing pin must be replaced.

(3) Mechanism wedged fast in third position.
This is a rare stoppage. The slide cannot be moved forward nor backward. It occurs when any obstruction gets between one of the bolt supports and the bolt lock. As the slide is driven to the rear the bolt lock is wedged fast by the obstruction. This stoppage has been caused by a blown primer or by a piece of metal broken off the rear of the firing-pin channel wall. It should be reduced in a properly equipped shop.

d. Fourth position.

(1) Failure to extract.
This stoppage is generally due to a dirty or pitted chamber. Usually, the empty case will have a small part of the rim pulled ofi by the extractor. This case can be removed only by the use of the cleaning rod. A few drops of oil in the magazine will ordinarily prevent this stoppage, temporarily. The only permanent remedy is a thorough cleaning of the chamber. If the gun develops this stoppage before a large number of rounds has been fired, it is not the fault of the gun, but is due to improper cleaning after the last firing.

(2) Failure to release sear.
Another fourth position stoppage is that in which the piece is cocked and the trigger mechanism will not release the sear when set at A or F. This stoppage is traceable to trouble in the trigger mechanism and may be due to a broken sear spring, a broken or lost connector, an improper assembling of the sear spring, or to any cause which has the effect of moving the middle prong of rthe sear spring too far to the front with respect to the connector, so that the connector is not cammed under the tail of the sear.

(3) Wedged primer.
Another fourth position stoppage occurs when a blown primer wedges itself between the points of the ejector and the face of the bolt, thereby holding the bolt mechanism back in the fourth position.

33. Immediate Action.

a. Definition and purpose.
Immediate action is the unhesitating application of a probable remedy for a stoppage. It is taught as a drill. Training in immediate action is designed to train the soldier to apply the proper immediate action without trying to figure out the cause of the stoppage. Any soldier who has learned immediate action as a drill, can keep the rifle in operation without a thorough knowledge of stoppages. Immediate acti,m will reduce practically all normal stoppages.

b. Rifle fails to fire.
Pull the operating handle completely to the rear and then push it forward. Tap the magazine fully home. Aim and fire. If stoppage recurs., pull back the operating handle slowly to determine position of stoppage, remove the magazine, and apply proper remedy as explained below.

(1) First position stoppages. 1£ the stoppage is in the first position, pull the operating handle all the way back and watch the ejection.

(a) If nothing is ejected, change magazine.
(b) If a loaded shell is ejected, change the firing pin.
(c) If an empty cartridge case is ejected, examine and correct the adjustment of the gas cylinder, turning it to the· next larger port if necessary.

(2) Second position stoppages.
1£ the stoppage is in the second position, feel for and remove the obstruction or burr on the face of the bolt, in the rear of the chamber, in the bolt lock recess, or on the bolt lock.

(3) Third position stoppages.
If the stoppage is in the third position:

(a) Use the ruptured cartridge extractor to remove the front part of a ruptured case from the chamber. If no ruptured cartridge extractor is available, oil and sand the nose of a bullet, put it in the chamber, and let the bolt go forward. Pull back the operating handle. This will usually extract the ruptured case. Clean and oil the chamber after doing this.

(b) If the stoppage recurs and is not due to a ruptured cartridge, examine the face of the bolt for an obstruction.

(4) Fourth position. If the stoppage is in the fourth position:

(a) If the slide moved after the trigger was pulled, use a cleaning rod to push the cartridge case &om the chamber. lf this stoppage recurs, clean the ammunition, clean and lightly oil the chamber with a rag.

(b) If the trigger cannot be pulled, or if the slide did not move when the trigger was pulled: See if the change lever is set on "Safe." Take out the trigger guard, and correct the fault in the trigger mechanism.

34. Position Stoppage Setups.

In the setups given below it is assumed the firer has alrcady executed the first step of his immediate-action procedure. He should be required to go through with his second step.

a. First position stoppagcs.

(l} Place a blown primer between the lips of the magazine and the top cartridge. Let the bolt go forward. Replace the magazine. Answer: Failure to feed-change magazine.

(2) Load the gun with a dummy cartridge. Let the bolt go forward. Replace the magazine.

Answer: Failure to fir~hange the firing pin.

(3) Place an empty cartridge case in the chamber. Let the bolt go forward. Replace the magazine.

Answer: Insufficient gas-correct gas adjustment.

b. Second position stoppage.
Place a blown primer on the face of the bolt or up in the locking recess. Let the bolt go forward. Replace the magazine.

Answer: Obstruction- remove the blown primer.

c. Third position stoppage.
Cock the riflc, then place a ruptured case in the chamber. Replace the magazine. Let the bolt go forward.

Answer: Call for the ruptured cartridge extractor.

d. Fourth position stoppage.

(l) Cock the rifle. Insert an empty cartridge case in the chamber. Replace a loaded magazine. Have the man pull the trigger.

Answer: Call for the deaning rod-examine extractor.

(2) Set the change lever on Safe.

(3) Remove the connector from the trigger guard or have the middle prong of the sear spring resting on the wall of the sear carrier.

Questions

1. What is a s,toppagc? Name five causes of stoppages.
2. What is headspace and what is the effect of excessive headspacc?
3. Explain how stoppages are classified according to the position of the bolt when a stoppage occurs.
4. What are the causes of:
a. Failure to fire.
h. Failure to feed.
c. Insufficient gas.
5. Name two causes of third position stoppages.
6. Name two causes of fourth position stoppages.
7. What is immediate action?
8. Explain the first step of immediate action.
9. When is the first step of immediate action applied and what percentage of stoppages will it correct?
10. Explain the second step of immediate action.