5.56 mm low maintenance rifle usa 1973

7/29/2019 5.56 Mm Low Maintenance Rifle USA 1973

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TEQ1N I CAL fVLANUALOPERATION AND MAINTENANCE

5.56mmLOW MAINTENANCE RIFLE7 MARCH 1973

CONTRACT DAADOS-71-C-0260

SYSTEMS GROUI'

-

SYSTEMS GROUP OF TRW INC . ONE SPACE PARK, REDONDO BEACH. CALIFORNIA 90278 (213) 535-4321


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TE 0--kJ I CAL t ~ UALO P E R A T I U f ~ AND f Y l A i i ~ T E N f t N C E

5.5 mmLOW MAINTENANCE RIFLE

7 MARCH 1973CONTRACT DAADOS-71-C-0260

Prepared forDefense Advanced Research Projects Agency

andU.S. Army Small Arms Systems Agency

by

SVSTEMS GROU,.,

SYSTEMS GROUP OF TRW INC ONE SPACE PARK, REDONDO BEACH. CALIFORNIA 90278 (213 ) 535-43211


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TABLE OF CONTENTS

1.0 INTRODUCTION2.0 DESCRIPTION OF THE RIFLE3.0 GENERAL DATA4.0 FUNCTIONAL SEQUENCE5.0 PREPARATION FOR USE

5.1 Receiving Inspection5.2 Servicing Procedure

6.0 OPERATING INSTRUCTIONS6.1 Firing the Rifle6.2 Immediate Action lnof Malfunction case6.3 Sight Adjustment and Zeroing6.4 Bayonet Instal lat ion

7.0 MAINTENANCE INSTRUCTIONS7.1 Disassembly Instructions

Magazine removalButtstock removalOperating sl ide group removaland disassemblyTrigger group removalGas cylinder plug removal

7.2 Assembly Instructions7.3 Maintenance Instructions

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Figure If

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LIST OF FIGURES

Low Maintenance Rifle , Right SideLow Maintenance, Rifle , Left SideLMR & Accessories in StorageContainerFront Sight Adjustment ToolSight Tool Instal led for ZeroingFacsimile of Ins truction Card forSight ToolBayonet Attached to Gas CylinderLMR - Par t ia l ly Exploded ViewMagazine RemovedButtstock Pin WithdrawnButtstock RemovedTakedown Latch - LatchedTakedown Latch-UnlatchedOperating Slide Group WithdrawnBolt & Locking Wedge SeparatedRetainer Spring RemovalTrigger Group RemovedGas Cylinder Plug RemovedLMR Field Stripped

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22

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1.0 INTRODUCTION

Technical ManualOperation and Maintenance

5.56mmLOW MAINTENANCE RIFLE

73.4300.10-6

This manual provides operation and maintenance instruct ionsfor the ARPA/TRW Low Maintenance Rifle , 5.56mm. I t contains adetai led descr ipt ion of the r i f le and i t s general charac ter i s t i cs ,procedures for disassembly and assembly, operat ion and functioningof the r i f le , types of ammunition and maintenance9 Throughout thetext the r i f le wil l be referred to as LMR.

2.0 DESCRIPTION OF THE RIFLEa) The r i f l e , LMR (Figures 1 and 2) is a 5.56mm magazine-fed,

ga s operated, air-cooled, shoulder weapon. I t is designed for us eonly as an automatic weapon and functions from the open bol t posit ion. I t accepts the same 20 an d 30 round magazines as the M-16ser ies r i f l e s , but they are inser ted from the l e f t s ide ra therthan the bottom. The LMR is adapted to the Bayonet M6.

b) The LMR is equipped with a flash suppressor/compensatorand a dust cover for the eject ion port which is automaticallyposit ioned.

c) The r i f le i s fabricated from corrosion-resistant mater ialsand is semi-permanently lubr icated by the dry film process.

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FIGURE 1. LOW MAINTENANCE RIFLE, RIGHT SIDE

FIGURE 2. LOW MAINTENANCE RIFLE, LEFT SIDE

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3.0 GENERAL DATAa) Weights

Rifle without magaz1neEmpty (30 round capacity)agaz1neFull magazine ( 30 rounds)Firing weight (fully loaded)Bayonet, M6Scabbard, M8Al

b) LengthsRifle and the bayonet, M6Rifle overal l with flash suppressorBarrel (without flash suppressor)

c) Sights

7.26 lb.24 lb. 74 lb

8.0 lb.6 lb. 3 lb

40.0 in34.3 in19.4 in

Front - post adjustable + 5 mils for zeroRear - dual range peep 0-300 meters, 300-500 metersSight Radius: 21 inches

d) AmmunitionCaliber 5.56mm (complete round)Project i leTypes

e) Performance Characteris t icsMuzzle speedMuzzle energyCyclic rate of f ireMaximum rate of f i reSustained rate of f ireMaximum rangeMaximum effect ive range

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182 grains55 grainsBall Ml93

Tracer Ml96

3250 f t /sec1290 f t - lb

450 rounds/minute~ 1 2 0 ronnds /minute"" 30 ronnds/minute2650 meters

460 meters


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4.0 FUNCTIONAL SEQUENCEStar t ing with r i f le in the seared pos i t ion , pull ing the t r igger

rotates the sear nose downward out of engagement with the bol t face.This allows the spring wrapped around the operating rod to drive theoperating s l ide , e jec t ion por t cover, an d bo l t assembly forward,str ipping a round from the magazine and ramming it into the chamber.As the car tr idge shoulders in the chamber, the ext rac tor claw r idesover the rim of the case and snaps into the extractor groove. Atthe same time the locking wedge forces the locking ro l le r s par t ia l lyout of the bol t up an d down into recesses in the receiver to lockthe bol t . Continued forward motion af ter locking causes the s t r ike r ,located on the front of the locking wedge, to protrude through ahole in the bol t face and impact the primer of the chambered car tr idge.

The car tr idge f ires an d drives the bul le t down the bar re l . Asit passes a por t in the r igh t s ide of the bar re l near the muzzle,some of the powder gas i s diver ted into a cyl inder on the r ight s ide.This drives a pis ton attached to the operating s l ide assembly rear-ward. For the f i r s t 1/4 inch of rearward t r ave l the operating s l idemoves independently of the locking wedge. For the next 0.3 inch, thewedge is being withdrawn but continues to support the ro l le r s holdingthe bolt locked. During th is period the pro ject i le exi ts the boreand the pressure decays. After 3/4 inch of s l ide t r ave l the wedgeno longer supports the ro l le r s an d the operating s l ide col l ides withan d picks up the bol t . This cams the ro l lers into the bol t to unlocki t . Continued motion opens the bol t to extract the car t r idge . After3-1/4 inches of bol t t r ave l the f ired case contacts a s tud on thereceiver an d i s ejected to the r ight through a port in the operating

., . ds..:...1 e . After eject ion the bolt an d sl ide continue rearward, pickingup the eject ion por t cover an d carrying it rearward to close the por t .Normally, the operating spring stores the moving par t s energy an dstops them jus t pr ior to s l ide contact with the butts tock, which actsas a buffer . I f the t r igger remains pulled, the spr ing relaxes an ddrives the mechanism forward to repeat the cycle unt i l the magazinei s empty. I f released, the sear stops the bol t jus t to the rear ofthe eject ion posi t ion and with the eject ion por t closed.

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5.0 PREPARATION FOR USEThis sect ion contains receiving inspection requirements and

servicing procedure for the LMR.5 .1 Receiving Inspection

The r i f le i s provided with a r igid plas t ic foam-lined shippingand storage container (Figure 3) which contains the r i f le , s l ing ,bayonet with scabbard, a 20-round magazine, and a 30-round magazine.Upon receipt of the r i f l e and accessor ies , ver i fy that nothing hasbeen damaged during shipment. Report a l l damaged or missing itemsto responsible personnel.

r ( nmr,

..FIGURE 3. L}ffi AND ACCESSORIES IN STORAGE CONTAINER

5.2 Servicing ProcedurePerform the following servic ing procedure af te r verifying that

there are no damaged or missing items.

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a) Remove any preservat ive, corrosion, or f i r ing residue fromthe weapon and i t s accessor ies .

b) The r i f le i s designed to operate without o i l under normalconditions. I f necessary, retouch the dry film lube using the spraycan of dry-lube in the tool ki t .

6.0 OPERATING INSTRUCTIONSThis sect ion contains ins t ruc t ions for f i r ing the LMR, an d

adjust ing an d zeroing the s igh ts .6.1 Fir ing the Rif le

The mechanical arrangement of the r i f l e and i t s e jec t ion pa t te rnare such tha t it i s normally intended for r igh t hand f i r ing . In casel e f t hand f i r ing i s attempted, keep the face clear of the ejectedcases. Perform the following steps to f i re the LMR.

a) Examine bore and chamber to ver i fy tha t the bar re l i s freefrom foreign mater ia l .

b) Check ammunition for corrosion or foreign matter .c) Verify safety lever ( located a t l e f t rear of pis to l grip)

i s on safe (down) and the bol t is in the open posi t ion.d) Inser t loaded ammunition magazine unt i l locked by magazine

la tch.e) Position safety lever in the f i re (up) posi t ion.f) Align r i f le on ta rge t and f i re by depressing t r igger .

WARNINGThe LMR functions only in the automatic mode, i . e . ,i t wi l l continue to f i re un t i l the t r igger is releasedor the magazine is empty.

6.2 Immediate Action in Case of MalfunctionThe following sequent ial procedure should be observed by the

shooter in case of malfunction:

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a) Keep the r i f l e pointed in a safe direct ion.b) Remove the magazine.

..c) Wait 5 seconds in case of hangfi re .d) Retract the operat ing s l ide and verify sear engagement.e) I f eject ion is not observed, check chamber and action

visual ly for possible presence of l ive cartr idge or f ired case.Remove or f i re out i f present .

f) Replace magazine and resume f i re .6.3 Sight Adjustment and Zeroing6.3 .1 Range Adjustment

The rear s igh t consists of two peeps on a pivot so that on ei s raised as the other is lowered. The unmarked peep is intendedfor ranges to 300 yards; the on e marked L i s for ranges 300-500yards.6.3.2 Zeroing Adjustments

The front s ight i s adjustable to zero the s ights only, usingthe adjustment too l (Figure 4) in the spares and tool ki t . Figure 5shows the tool ins ta l led on the front s ight for adjustment. Theinstruct ion card accompanying the tool provides deta i led data onhow to adjust the impact pat te rn , f i r s t for ver t ica l and f inallyfor l a te r a l posi t ion. I t is reproduced as Figure 6.

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n Lr

in pd


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INSTRUCTIONS FOR USE OF LMR (1)SIGHT ADJUSTMENT TOOL1. Vert ical Adjustment (perform f i rs t )a. Loosen jam nut with wrench.b. Insert s ight wrench inside nutwrench and make desired correct ion. Each fu l l turn of s igh t wrench moves

impact 1 mil in direct ion indicated onstem. Make ver t ica l adjustments inunits of one fu l l turn only.c. Hold sight wrench fixed andt ighten nut wrench. (over)

INSTRUCTIONS FOR USE OF LMR (2 )SIGHT ADJUSTMENT TOOL (CONTINUED)2. Lateral Adjustments (perform af ter

ver t ica l adjustment described onreverse).a. Loosen jam nut unt i l red do tl ines up with zero on dia l of s ight

wrench.b. Make desired correction usingdot as reference, by turning s igh twrench as indicated on dia l .c. Hold sight wrench fixed andt ighten nut wrench. (over)

FIGURE 6. FACSIMILE OF INSTRUCTION CARD FOR SIGHT TOOL

6.4 Bayonet Ins ta l la t ionThe bayonet M6 may be attached to the r i f l e as shown in

Figure 7. The r ing on the guard engages the ga s cylinder plugand the la tch in the bayonet handle engages the lug on the rearof the gas cylinder.

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FIGURE 7. BAYONET ATTACHED TO GAS CYLINDER

7.0 MAINTENANCE INSTRUCTIONSThis sect ion provides instruct ions for disassembly and

assembly of the LMR an d maintenance requirements an d procedures.7.1 Disassembly Instruct ions

The LMR ca n be eas i ly and quickly disassembled into 6 majorgroups, namely: magazine, butts tock, operating s l ide group,t r igger group, gas cyl inder plug and barrel- receiver group. Thedisassembly can be accomplished in a number of different sequencesbut wil l be out l ined in the above order. Refer to exploded viewFigure 8 for par t s and nomenclature.

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Ir--ar--aI

TRWSYSTEMS GltOUP

LOW MAINTENANCE RIFLECAL . 5.56 MM

10 """'[~ ~ - ~ _ / /8 //

/ J/

FIGURE 8. LMR - PARTIALLY EXPLODED VIEW

. ~.... ~

- ~ - >I. MAGAZINE2. BUTISTOCK PIN3. BUTISTOCK4. OPERATING SLIDE5. BOLT6. EJECTION PORT COVER7. LOCK ING WEDGE8. RETAINER SPRING9. PIN10. TRIGGER GROUPII. GAS CYLINDER PLUG12. WASHER13. RECE IVER AND BARREL GROUP


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Magazine Removala) Depress magazine release catch and simultaneously withdraw

magazine (Figure 9).

FIGURE 9 . MAGAZINE REMOVED

Buttstock Removala) Depress center lock post of butts tock pin and simul

taneously withdraw butts tock pin from butts tock (Figure 10).

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FIGURE 10. BUTTSTOCK PIN WITHDRAWN

b) Pul l bu t t s tock rearward to complete removal (Figure 11).

FIGURE 11. BUTTSTOCK REMOVED-13-


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Operating Slide Group Removal and Disassemblya) Push forward and rotate take down la tch on operating s l ide

1/4 turn counterclockwise (Figures 12 and 13).

FIGURE 12. TAKEDOWN LATCH - LATCHED

FIGURE 13. TAKEDOWN LATCH - UNLATCHED-14-


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b) Withdraw operat ing sl ide assembly, bol t and locking ~ e d g eby sl iding rearward (Figure 14).

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FIGURE 14. OPERATING SLIDE GROUP WITHDRAWNc) Separate bol t from operating sl ide drive stud.d) Remove locking wedge from bol t by s l iding to rear (Figure 15

.FIGURE 15. BOLT AND LOCKING WEDGE SEPARATED-15-


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e) Sl ide eject ion port cover rearward out of i t s weapontrack in the receiver i f it did not come free with operat ings l ide .Trigger Group Removal

a) Depress front end, ro ta te , and remove re ta iner spring(Figure 16).

FIGURE 16. RETAINER SPRING REMOVAL

b) Remove pin from t r igger assembly body.c) Pul l t r igger and s l ide t r igger assembly rearward andremove (Figure 17).

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I

FIGURE 17. TRIGGER GROUP REMOVEDGas Cylinder Plug Removal

a) Unscrew and remove gas cylinder plug and washer using5/8" open-end wrench (Figure 18).

FIGURE 18. GAS CYLINDER PLUG REMOVEDDISASSEMBLY COMPLETED. This completes f ield disassembly of theLMR (Figure 19).

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Further disassembly i s not normally required except for repa i r orparts replacement, which should be normally accomplished byordnance personnel.7.2 Assembly Instruct ions

To assemble the weapon the above procedure i s reversed, takingcare to i ns t a l l the eject ion port cover as indicated thereon andwith i t s drive lug trapped between the driving lugs on the opera-t ing s l ide .7.3 Maintenance Instruct ions

The LMR, as the name implies, requires only minimal maintenance to insure re l iable functioning. Components are ei thercorrosion res is tan t or provided with protect ive coatings againstnormal corrosive environments. The bar re l bore an d chamber arehard chrome plated to minimize not only corrosion but erosionfrom automatic f i re an d buildup of powder fouling.7.3.1 Cleaning

Occasional cleaning of the moving parts is necessary toremove accumulated powder foul ing, brass shavings from the cart r idge cases, an d foreign matter such as dust. Fresh water anda toothbrush or l in t - f r ee rag are recommended cleaning implements.Particular a t tention should be given to the gas piston an dcyl inder , where powder and metal fouling ca n build up, especial lywhen f i r ing t r acer rounds. Use of a wire bore brush or metalscraper , inser ted through the access hole on the front of t ~ ecyl inder , is recommended. Snapping the mechanism several t imeswith the r i f le unloaded wi l l also help to clean this buildup offouling in the cyl inder .

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7.3.2 LubricationThe r i f l e has a semi-permanent dry film lubr icant applied

to wearing surfaces .tend to col lec t di r t .

I t i s superior to o i l because it does notAt approximate 2000 round intervals this

should be inspected an d touched up in high wear areas using thespray ca n of dry film lubr icant contained in the spares and toolki t . In l ieu of the above, a very small amount of LSA or otherl igh t small arms o i l may be applied to the bo l t , ro l l e r s , locking wedge, and s l ide area, except in extremely cold environments where the o i l might freeze. As with other r i f l e s , theLMR wil l not operate when clogged with dust , sand or mud.Keep it clean!

5.56 mm low maintenance rifle usa 1973

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