20 mm. A.A. Gun

255 Pages·1943·20.389 MB·English

ORDNANCE PAMPHLET NO. 911
20 mm. A. A. GUN
20 MM. MACHINE GUN MECHANISMS MARKS 2 AND 4
20 MM. GUN BARRELS MARKS 2, 3, 4, AND 4 MOD. 1
20 MM. SIGHTS MARKS 2, 4, 4 MOD. 1, AND 5
20 MM. MAGAZINES MARKS 2 AND 4
20 MM. SHOULDER RESTS MARKS 2, 4, 5 AND 5 M09
DESCRIPTION
MARCH, 1943
SHIELD
CLAMPING LEVER--
--- COCKING WIRE ROPE
ZO mm. A. A. Gun on Mark 4 Mod. 3 Mount
PREFACE
Thi:: OrC::::~.:-:cc Pa;..i=::~c: ;\o 911. is:" re\'ision of the Gun Section o( Ordnance P<lmphlcr ~o. s:J
and dc:sc::bd the c.;~~:: _c:. • :. <.....::;u:i..r:, ;md miJ,intena.nce of rhe 20 nu11. A.A. Guns.
:1-ddi~:..;:-.... (::~;.-:c-e p..:O:!c~tions re!~tins: co the use of the 20 mm. A.A. Guns ate:
O.P. 909 -~ "'"'· ~lounts )lark 2. Mork 2 Mod. I, Mark 2 Mod. 2; Mark 4, Mark 4 Mod. I.
~:.rk <~led. 2. Mark 4 Mod. 3: Mark 5, Mark 5 Mod. I, Mark 5 Mod. 3, Mark 5 ~led.
; ~l>rk 6; Mark 10 and :Vlork 10 Mod. !.
-20 mm. A.A. Range Tables.
0.0. H29 -Gun Sight Mark B Mod. 2-1n stallMion and Opemrion.
st..:. ~o. 103308-20 mm. Ylachine Gun and Mount lndex.
Ordalt No. 118&-20 mm. Cradles M.:t.l'ks 2 and 4-[nstn>Ctions ior :Neces:sary ModifiC:.1tion for .'\!;sembly
of Cun Sight Mark B.
Ordalt No. l226- 20 mm. Machine Gun Mechanism :".l:'l.rks 2 a:ld 4-20 mm. Hand Grip$ and Shuutd~:
R. .. -sts :\larks 2 ~utd 4-ln:ilructions {or :\ddin~ Ur..inagc Hole~.
Ordalt :-lo. 1260-20 mon. Cradle ~lark 2 and ~lork 2 :11od. I.
20 mm. Cradle )r::t.rk -4 o.nd ).lark 4: .:Vtod. 1-lnstructions for l11~t."l!lation of Cock1ng
Shelve.
Ord.n.lt Xo. 1300-20 mm. Shield ;\(ark 2:20 mm. Shidd 2\f:l.rk 4.-l;lscruccioll:s for ~£<>dific:uion ol Shic.C
Br.~.<:keu.
Ordalt Xo. 1366-20 mno. Cradle ~l~rk 2 >nd ~lark 2 )1od. I.
20 mm. Cr.~.dlc ).·lark 1: J.r.d ).J:Jrk -1. ).1<...-.d. 1- lnstructions for Cradle ;.\Iodili.c:don t'-'
Facilic:ue Diuss~mbly.
Ordalt No. 1395-20 mm. Shields Marks 2 and 4-lmprovement of Sigh c.
Ordalt No. 1398-20 mm. Mounts :\larl.."S 2·and 4-Chal\ge$ co Improve Lubrication.
Ordalt 2\'o. 14$i-2\lodi:!i.C;ttioa of 20 mm. Sight ).l;..rk 4 Mod. 1.
The :\1ark l Gun was the origln3l type made in Swic~rland. The :vi'ark 2 is i:he improv'!d .. ~~~·
n1adc in England and also being made io U.S. A. The Mark 4 Gun is almost identical w:;h 2\Ld.: 1 .:. . ~-•
ior !lightly different mnnufacturing limits. Both :\larks 2 and 4 Guns will bt: found in s~rv:ke .n ~'1~: :._· !
:\o.vy, but eventuaJir only the :\1ark 4 wiH bt: manufactured in this cuuncry.
\
L
-
INTERCHANGEABILITY
There is very little difference, [rom the opero~ing point of view, between
Mark 2- British
Marks 2 and 4-U. S. N.
All o[ the above three Marks or assembled guns nre inte:changeable as units. There arc certain
differences in the Marks 2 and 4 guns that affect intcrchangeabiitt;- of parts. When individual parts are
not interchangeable between Marks 2 and 4, the auembly or the !CO<l$Sembly containing thcoe parts is
usually interchans<'able.
AMMUNITION
The ammunition is common for M:ltks 1 and 2 (British) and :\b:::. 2 a~d ~ (t,;, S. N.) Guns.
TABLE OF CONTENTS
NOT.E-Plore I is the folded insert of the 11,un osscmbly at pn~c 160.
Test IIIUJ.
P:a.ie Fl&. ~·o
F rontispieee. . . . . . . . . . . . . . . . . . . . . . .. . . . . • . . • . .. . . • • . . • . . . . . • . . . . . . .. • . .. .. .. 2
Preface .. .. ...... .......... ... ....... ........................................ 3
Chapter 1
OAT:\
•
Gun Firing Rate. . . .. . . .. .. . . . . . • . . . .. . . . . .. . .. . . . . .. . . .. .. • . .. . . . . .. . .. . .. . . 11
~l3ga:int C:a.pacity. . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . • . 11
G>n Barrel lhta . . . . . . . . . . • . . . . • . . • . . . .. . . . . . . . . . . . . . . . . . . . . . . . . 11
R~nge Data. . . . . . .. . . . . .. . . • . . . . . . . . . . . . . . . .. . . . .. . . . . . . .. . • .. . .. . . . . . . .. . 11
\\'eights of Components .........•....•.. .... ...... ............................. 12
Chapttr 2
CENER.-\L DESCRIPTION OF
CU~ OPERATION
Featuru...................................... . ................... .
·~
Principle of Construction . . . . . . . . . . . . . . . . . . . . • • . . . . . . . . . . . . . . . . . . . . . . • . . . 15 2
Firing Fe::.tures. . . . . . . . . . . . ......... , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Gun- Com;truction-Gencral Description. . . . . . . . . . . . . . ...................... . I• o. P!at< 1
Nlagazi.ne-General Descriplion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
~1ount........... . . .........................•........ 15
Operating Fearu~es .................................................. . 17 3+5-o
Chapter 3
Gl-:\ :\IECH:\.'\IS:\1
Trigge~ :\locoar.i;r:: 23
Recoiiir.g ~lec:-t.1:::sm 23
G"n Bar:el :"or::e"c:~:-~= 23 9
G. . m Barre: Co:1s:.:-.:c:~:-: :?~
Gun Barre: Re;:.k:-t=-::t:.: 25 !0 a:-:ci t?
Ba~rel Stop Pin 20 11
Barrel Locking ~,, 26 8
s,c;:
Double Loading 26 20 tO 23
Breech Caaing. . 27
Gu:1 Mounting .J..~:ac."':::-:~~!! 2S 13
,"d
~laguiae Catch ~a: E'•=:c: 29 14 to 18
.,_
Ejector and Cartridge Ejec:i~n '? 19
Magazine Interlock ~ar Oooro::or. . 33 16-li
Hamme: Plate Operation · 34 44-45
Double Loo.ding Stop Operatioo. 34 20 to 23
CONTENTS PAGe 5
TABLE OF CONTENTS
Ch~pter 4
TRIGGER ~IECH.<\.:'IISM Jllus.
fi&. ~o.
Trigger Mechanism ....................... . 39 24
Trigger Function ................ . 40
Cocked Position .....•............. . . . . . . . . . . . . • . . . . • . . 42 24-25
Firing Action ...................... . 12 26 to 31
Snle/Fire Gear. .............. . .. ···•···· ............. H 32
Mn gazine Interlock Gear F :.mc:io~: 48
Magazine Interlock Gea: .>.c:ion 48 33 to 42
.~ I nga.z.m e I nter Io ck · \\""J :..r .c. .:a.,,·a... \\..~ e:: .l. ::.:.~ :.; ;:::.: -.; .'• I a;.:.:;:-.: .\•0 . .................. ' .. 52
RECOIU;\G P.\RTS .\.'\D Bt:FFER
("nmronentF ~7 43
.;s
:;triker Gear. H-45
..
Breech Dlock . .......... . 39 44--15
B rccch Burs . . ........... . .;g 43
Barrel Springs and Case .. ~9 43
Recoil Buffer Springs .. 61 46
Trigger Buffer Springs .. ......... 61 2-!
Ch3pter 6
Opcrntion. . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . .........•...... 65 47
Feed Action. . . . . . . . . . ...... , . . • . • . . • . • . . . . . . . . . . . . . . 65 47
Mng:uine Clock Spring. . . . . .. . . .. . .. . . . . .. . . . . . . . . . . . • . . . . 65 47
Cartridge Feeder. . . . . . . . . . . . . • . . • . . . . • . . . . . . . . . . . . . . . . 65 47
Spring Tension limits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 47
Loading.............. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 66 48 to 56
Completely Tensioning a ~lagazine Spring . . . . . . . . . • . . . . iO 5S
Spring Tension Indicator.... . . . . . . . . . . . . . . . ...... , ........ , il 47
Slight Initial Tensioning ol a :'>!ngazine Spring. . .......•..•..... i l 58
Relieving the Magazine Spring Tension. . . . . . . . . . ................ 72 59 to 61
Unloading a Fully Tensioned nnd Completely Filled :l!~gnzi~e ................... 73 62
Unlooding a Completely Filled Magazine Having lnitinl S~r:ng Tensioning ..... , .... 73 63
Unloading a Fully Tensioned and Pnrtly Filled Magazine..... . .................. 73 62
Stripping a Magazine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............... , .... 74 64 to 67
Re>ssembling a Stripped Magazine . . . . . . . . . . . . . . . . . . . , .................... 77
Chansing- Ylagazines . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . . . . . . . . . . 78
)lagazine Maintenance. . . . . . . . . . . . . . . . .. . . . . . . . . . . , . • . . . . . . . . . . . . . . . 78
Magazine Corroded or Dry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . •................ iS
Magazine Clock Spring-<:are or. ............. , ..... , , .......................... 78
~!agazine Interlock Bolt-Care of. .............................................. 78 35
Magazine Lubrication ....................... ................................... 78
PAGE 6 CONTENTS
TABLE OF CONTENTS
Cb:~pter 7
Tut
SICH.T
Page
Description......... .............................................. 82 68-69
Usc of Sights Mark 2, Mark 4, and ;>.lark 4 ;>.lod. I................... .. ...... 83
Shipping and Unshipping :he Sight- :-.lar;, 4 and ~lark 4 Mod. 1 ................... 83
Preparing Sight for Stowir.g-~lark 4 a~d ~lark ~ :\lod. I .......................... 83
Replacement of For0$ight-Mark ~- ~lark 4. and ~lark ~ Mod. 1 .... ..•............ 85
Mark.; Sight- Description......... . ............................ 55 69
Mark 5 Sight-Operation....... ........ . .............................. 85
~lark 5 Si~rht-Servicing.. .. .. . .. . .. . .. . . . . . .. . .. .. .. .. . .. .. . . 87 70
Alternate Rear S!ght Tips...... . . . . . . . . . . . . . . . .. . . .. . . . .. . . . .. . $7
Bore Sighting......................... . .................... 88 ;1.12
Chapter 8
SHOt:lDER REST
Marks 2 and 4 Shoulder Rest Assemb>: . . . . . . . . . . . . . • . . . . . . • . . . . . 96
)<ia.rk 6 and Mo.rk 0 ~lod. 1 Shou!dc:- R.:n .\H~:l~bli..:o ................. ·•·•······ 90 73
Vertical Adjust.ment ........... . . .......................... 9i 73
Lateral Adjustmcn r. .......... . 97
Shoulder Pad Angular Adjustment.. 07
Instruction• for Use. . . . . 97 i-1 to 7i
Adjustment of Clamping Levers .. . ....... .. ...... .......... 101
Ch~pter 9
.-1.)1 )IL' );IT ro:-;
Am~unition Tvs>t' . . . . ...... . . ..................... 10<1
[A,dcd and Fuzed Projccile with T:-:1cer. .. .. .. .. • .. .. 1().1
Loaded and Fuzed Projec:.le without Tra<X'r .. .. .. .. . .. .. 10-1
Blind Loaded and Tr.>cer T;•pe Projectile ...... ... . 10<1
Blind Loaded ond Plu~ged Projectile .. . ............... 10-1
Propellant.. . ...... . 104
Ammunition Construction ............. . . •.••.•........ 105
High Explosive Shell. ................................ .. . ............... 105
Ammunition P:lcking. . . . . . . . . . . . . . . . . . . . . ...•.....•..... 105
L'np<~cking Cartridges .............................. . . . . . . . .105
Inspection or Cartridges.. .. .. .. . .. . .. . .. .. ............... .... 105
Grelting Ammun~tion.... . . . . . . . . . . . . . . . . . . . . . . . ........ ....... 105
::>ropping Cartrid~rcs.. . . . .. . . . . . . . . . . . . . . . . . . . . . .. ..... . 106
-:··~die R~it ............................... .. . . . . . . . . .106
=".:.·•~ Am::~unition Depot ................. . .. ................ 106
Chapter 10
GUN ~1.-\L'\TEN.\XCE lNSTRt,;CTIOXS
::~:.:::; :."": -~ .:-:i ~! G..lr
'\":·.!;- :: .... ~ ... - :."':: : ..
--=-=·
"'i
CONTENTS
TABLE OF CONTENTS
Chapter 10 (Contd.)
iext Jllus.
GUN MAJNTEI"ANCE INSTRCCTIONS
P::age: Fi&. No.
Double Loading Stop Parts Lubrication. . . . . . . . . . . . . ................... . .108 78
Double Loading Stop Geo.r and SuiTer Corrosion . . . . . . . . . . . . . . . . ..... •.... .108 78 and SO
Secur:ng Bolt Lub:ica<ion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................ 108
Barrel and'Barrel Spring-Care of............ ............ . ........... 109
Barrel Bore and Firing Chamber-Care of... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Muzzle Covers. . . . . . . . .. . .. . . .. . . .. . . .. ..... ........ JIO
S<op(»gcs-How <o Clear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 110
Use of Cartridge Extrac<ing Tool....... . . . . . . . . . . . . . . . . . . . ........... 110 79
Life of Barrel. . .. . . ...... 111
Gun Barrel Rcplactmt!nt ................... . • ....... 112
Gun Barrel Rcm0\'"3.! ............... . . ....... 112
Gu1l B::trrcl lnsr:tll3.tion .. ................. , .............. . . ..... l12
Violent Recoils... . . . .... 112
Buffer Corrosion . .......... . .113 80
Gun .Mounted on Submarine.. . . . . . • . . . . . . . . . . . . ..... .... . . ...... 114
Cleaning. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .. . . . . . . .. .. . . . .114
LubtiC'.J.tion... . . ................•........ .114
List of Gun C":.!stw.!ties ....................... ...... . 115
Chapter 11
COCKING AKD UNCOCKI~G THE GU:'\ ~IECH.-I..'IS~I
Cocking She=tvc 1\lethcd-Mounts \Vith Ad:usto.ble Tntnnions. .122 81-82
Cocking Sheove ~·lethod-Fixed Height :vtounts . ............. . . 125
Cocking Rope :'11ethod- \Vithout Cocking s:,eave . ............. . .125
Cocking l.nnyOlrd ~1~:-1:. 3....... ...... . ......... ........ . . .125
Hook and Rope Cocking Tool Mark 4 .. ..... ..•..•..•. .•..•. .••. .126
Block and Tackle Mark 2. . . .... .... ...... .................. .. .126 83
R:uchet Type Cocking Tool Mark 1 . . . . . . . . . . . . . . . . .. .. 127 84
Chapter 12
PARTIAL STR!PPI.'G
(See Pl3te 1, Pa~e 160)
Gun Tools................... ............ ....... . ............ ... 130 80
Breech Face Piece Removal ... ..... ... ..... .......... .......................... 131 86-87
Breech Face Piece Installation. ... .............. .. ................ . ..... 134 88
Barrel Spring Case and Cotter Securing Bolt and Retainer Remo•·al ................. 135 89 to 92
Barrel Spring Removal... . . . . . . . . . . . . . . . . . . . . . . . . . ............ ........ 137
Hand Grip Removal. ........................... ..... ................... ....... 137
Trigger Partial Stripping ...................... ....................... '. ...•..... 137 101
Breech Block, Bolt and Sear Removal..... . . . . . . . . . . . . . . . . . . . . . . ..... 138 101
Breech Face Piece Removal..... . . . . . . . . ......................... 138 Si
Striker Gear Removal.... . . . ..... .... ..................................... 138 95
PAGE 8 CONTENTS