tm 9-314 57-mm rifles, t15e13 and m18__75-mm rifles, t21 and m20 (t25) 19490322

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Figure 86. Breechblock and breechblock hinge-rifle M2O-exploded view showing extractor assembly.

I 05. Tabulated Data

a. DATA PERTAINING TO 75-MM RIFLES T21 AND M20.

(1) General.

Weight of rifle (w/sight bracket) ________________ Length of rifle_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Length of tube _______________________________ Length of rifling ______________________________ Twist of rifling, right-hand_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Number of lands and grooves__ ____ ~ ____________ Type of breechblock ____ ___ ____________________ Type of firing mechanism_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Ammunition _________________________________

(2) Performance.

Muzzle velocity: HE and WP rounds_______________________

. HE, AT rounds ___________________________

Range (approximate maximum) : Cartridge, HE, AT, M310 (T39) ____________ Cartridge, HE, M309 (T38) ________________ Cartridge, smoke, WP, M311 (T40) _________

114 . 5 lb. 82 in. 65.1 in. (22 cal.). 65.1 in. (22 cal.).

1 turn in 22 cal. 28. Interrupted thread. Percussion. For complete ammuni­

tion data, see para­graphs 161-169.

990 fps . 1,000 fps.

7,200 yd. 6,955 yd. 7,020 yd.

Estimated usable life: Tube_________________________________ _ Choke ring (T21) _______ ~ ______________ _ Vent assembly (M20) ______ __ __________ _

b. DATA PERTAINING TO CAL. .30 MACHINE M1917A1.

WeighL _____________ - - -- --- - - -- - - - -- - ---- -------- ­Maximum elevation _____ --- - - - - - -- - ----- - -- - - - ----- ­Maximum depression __ - - - - - - - - - - - - - - - - - - - - - - - - - - - - -­Traverse ________ - - - -. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ­Elevation per turn of elevating knob __________________ _ Traverse per turn of traversing knob _________________ _ Dimensions (when folded for transportation)

Length_______________________ __ _________ ______ _ Width ________________________________________ _ Height_____________________________ ___________ _

c. SIGHTING AND FIRE CONTROL EQUIPMENT.

On-carriage:

Direct fireIndirect fire

SIGHTUNIT, M34 LIGHT, instrument, M42 CASE, carrying, M78 QUADRANT, gunner's, M1

oif-carriage:

Infantry

BOARD, plotting, M10 BINOCULAR, M13A1 or

M17A1 CIRCLE, aiming, M1 TABLE, firing, 75-BB-1

(abridged) FINDER, range, M7 WATCH, wrist, 7-J WATCH, wrist, 15-J or more

120

________________

__________________ ___ _____ __________________________

____________________ ___________________

______________ ___ ______ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

____________________ ______

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and breechblock hinge-rifle M20-exploded view extractor assembly.

75-MM RIFLES T21 AND M20.

bracket) - - - -

grooves ---

- _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

M3lO (T39) ____________ (T38) ________________

WP, M3ll (T40) _________

114 .5 lb. 82 in. 65.1 in. (22 cal.). 65.1 in. (22 cal.).

1 turn in 22 cal. 28. Interrupted thread. Percussion. For complete ammuni­

tion data, see para­graphs 161-169.

990 fps. 1,000 fps.

7,200 yd . 6,955 yd. 7,020 yd.

Estimated usable life: Tube _____________________________ ____ ___ 5,000 rds. Choke ring (TIl) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 500 rds. Vent assembly (M2O) __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 500 rda.

b. DATA PERTAINING TO CAL..30 MACHINE GUN TRIPOD MOUNT M1917Al. WeighL _____________ _________________________________ Maximum elevation _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Maximum depression _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Traverse ______________________________________________ Elevation per turn of elevating knob ______________________ Traverse per turn of traversing knob _____________________ Dimensions (when folded for transportation)

Length____________________________________________ \Vidth _________________________________________ ___

Height_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

c. SIGHTING AND FIRE CONTROL EQUIPMENT.

53.2 lb. 27 deg. 65 deg. 360deg or 6,400 mils. 25 mils. 25 mils,

36 In. 10 In.

19.5 in.

On-carriage:

Indirect fire

SIGHTUNIT, M34 LIGHT, instrument, M42 CASE, carrying, M78 QUADRANT, gunner's, Ml

Off-carriage:

Infantry

BOARD, plotting, MlO BINOCULAR, M13Al or

M17Al CIRCLE, aiming, Ml TABLE, firing, 75-BB-l

(abridged) FINDER, range, M7 WATCH, wrist, 7-J

.WATCH, wrist, 15-J or more

Direct fire

MOUNT, telescope, M78 TELESCOPE, M85C LIGHT, instrument, M36 CASE, carrying, M79

Airborne

BOARD, plotting, 1\110 BINOCULAR, M13Al or M17 Al CHEST, lighting equipment, M21 CIRCLE, aiming, Ml TABLE, firing, ·75-BB-l

(abridged) COMPASS, M2 WATCH, wrist, 7-J WATCH, wrist, 15-J or more

121

BR

,REECHBLOCK HI

CAM ROLLER - l S II A7229116 .

OPEN BREECH LOCK

OPEN BREECH LOCK SPRING - A7229126

RA PD 108000

Figure 87. Breechhlock and breechhlock hinge-rifle Mfl-e:eploded view 81wwing open breech lock and 8pring.

CHAPTER 6

OPERATING INSTRU

Section I. GEN

106. Scope

Chapter 6 contains information for the responsible for the operation of this equipment. on the operation of the equipment, with the the controls and instruments.

Section II. SERVICE UPON RECEI

107. General

a. Upon receipt of new or used materiel it is officer in charge to ascertain whether it is condition. A record should be made of any malfunctions, and any such conditions should I as possible.

b. Attention should be given to small and mm most likely to become lost and may seriously affe~ of the materiel. I

c. The materiel should be cleaned and prepar/ ance with instructions given in paragraph 108 01

108. New Materiel

a. Rifles received from storage will usually bJ preventive. They will be serviced as follows: 1

(1) Remove and disassemble breech operati lined in paragraph 141 and breechblo paragraph 143 (T21) or 145 (M~O).

(2) Clean by removing corrosion preventive 14.

122

CHAPTER 6

OPERATING INSTRUCTIONS

BR ,:I"... n DLU\_" '",­

OPEN BREECH LOCK

OPEN BREECH LOCK SPRING .. A12~9126

RA PD 108000

breechblock hinge-rifle M21-ezploded view showing open breech lock and spring.

Section I. GENERAL

106. Scope

Chapter 6 contains information for the guidance of the personnel responsible for the operation of this equipment. It contains information on the operation of the equipment, with the description and location of the controls and instruments.

Section II. SERVICE UPON RECEIPT OF MAT~RIEL

107. General

a. Upon receipt of new or used materiel it is the responsibility of the officer in charge to ascertain whether it is complete and in operating condition. A record should be made of any missing part<> and of any malfunctions, and any such conditions should be corrected as quickly as possible.

b. Attention should be given to small and mmor parts as these are the most likely to become lost and may seriously affect the proper functioning of the materiel.

c. The materiel should be cleaned and prepared for service in accord­ance with instructions given in paragraph 108 or 109.

108. New Materiel

a. Rifles received from storage will usually be coated with a corrosion preventive. They will be serviced as follows:

(1) Remove and disassemble breech operating handle group as out­lined in paragraph 141 and breechblock group as outlined in paragraph 143 (T21) or 145 (M~O).

(2) Clean by removing corrosion preventive as ou tlined in paragraph 14.

123