Gunnery School Notes

MMcDermottC1119618-161216-11.pdf

Title

Gunnery School Notes

Description

A book used by Colin McDermott to record his notes from Gunnery school. Subjects covered include the Browning and Vickers guns, gun sights and their use, turrets, range standing orders and the Boulton Paul turret.

Creator

Language

Type

Format

One notebook with 136 pages of handwritten notes

Rights

This content is available under a CC BY-NC 4.0 International license (Creative Commons Attribution-NonCommercial 4.0). It has been published ‘as is’ and may contain inaccuracies or culturally inappropriate references that do not necessarily reflect the official policy or position of the University of Lincoln or the International Bomber Command Centre. For more information, visit https://creativecommons.org/licenses/by-nc/4.0/ and https://ibccdigitalarchive.lincoln.ac.uk/omeka/legal.

Identifier

MMcDermottC1119618-161216-11

Transcription

A Gunnery [indecipherable words] [underlined] Form 407. [/underlined]

ROYAL AIR FORCE.

Sgt [underlined] C McDermot [/underlined]

LARGE NOTE BOOK.

T.2322. Wt.1535 75,000 Bks – 5/38 W & S Ld (192476T.)

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[diagrams]

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BROWNING GUN

Type of installation .303 Mark II

A. As a fixed gun. e.g. wing installation cockpit installation
B As a free gun. e.g Turret installation

The gun is automatic in the sense that the continued operation of the firing control will cause all the available ammunition to be expended.

General description

Overal [sic] length 38 1/2 in. Length of Barrel 26”
Weight (with loaded mech). 22lbs 12 oz.
Rate of fire 1100-1200 r.p.m. [indecipherable word] 1/20 pm action
Rifling. Left hand 1 in 10

The parts of the gun are divided into two groups thus

Recoiling Parts
Breech Block
Barrel Group

Non Recoiling Parts
Barrel Tracing
Body
Back Plate
Breech Cover
Lock Frame
Return Spring

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[inserted] 14 Ta pressure [/inserted]

1/ [underlined] Action of Recoil Backward Movement [/underlined]

When a round is fired direct recoil action takes place and gas is momentarily trapped in the muzzle attachment, rebounding from cone of flash elliminator [sic], impinging on the end of the barrel. These coupling forces combining together, forces the Barrel, Extension and Breech Block to the rear. The latter being locked to the Barrel Extension due to the [deleted] locking of [/deleted] locking piece being held upwards by the locking piece cam, the “T” projection of the Barrel Extension bearing against the [inserted] barrel [/inserted] return spring.

2/ [underlined] Unlocking of the Breech Block [/underlined]

The Barrel.

Barrel Extension and Breech Block [deleted] are forced to the rear [/deleted] Are locked together as they move to the rear. The inclined position on the Locking Piece allows the L.P. to drop down the inclined surface of the inclined L.P. cam disengaging the LP. from the L.P recess on the B.B. This action is [inserted] ensured [/inserted] assisted by the prongs of the lock frame travelling along the cam grooves and the inclined surfaces on the prongs engaging the

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locking piece pin and giving it a definite downward movement. The B.B. is now free to move to the rear.

3/ [underlined] Backward Acceleration [/underlined]:- action of.

As the B & B.E. move to the rear the accelerator face on the B.E. comes into contact with the front face of the accelerators. Forcing the accelerator upward, backwards and over the centre. The horns of the accelerator arm strike the [indecipherable word] on the B.B. and assist in the backward movement of the B.B. As the accelerator moves backwards and over centre, [deleted] of [/deleted] the ramps engage behind the “T” piece projection locking the B. & B.E. to the lock frame.

7/ [underlined] Cocking Action [/underlined]:-

The tail of the cocking lever is engaged in the cocking lever bracket and the nose in the slot in the firing pin and as the B.B. moves back, the tail of the C.L. is forced forward causing the nose to move backwards and withdrawing the firing pin from the firing P. hole. This action causes the F.P. spring to be

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compressed [inserted] against the rear [indecipherable words] pin [/inserted]. The [indecipherable word] of the F.P. engages the rear pushing it clear and the F.P. continues to the rear where it is held by the nose of the cocking [deleted word] lever.

4/ [underlined] The backward action of the Transporter. [/underlined]

As the B.B. moves to the rear the claw on the transporter which is engaged in the front of the rim of the cartridge withdraws the cartridge from the belt The round being supported by the ejector. The transporter is prevented from falling by its plunger riding along the top transporter front cam. On reaching the chamfered face the plunger is depressed and the ramp on the cover forces the transporter down bringing a live round down onto the face of the B.B.

5/ [underlined] Extraction [/underlined] and Ejection

The case in the chamber is held by the cartridge rim guides and as the B.B. moves to the rear the empty case is withdrawn from the chamber and being unsupported is free to drop off the cartridge rim guides when sufficiently clear of the

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chamber. If it does not fall off the the [sic] rim of the live round bears on the rim of the empty case forcing it downwards. In the case of the last round it is ejected by the ejector

6/ [underlined] First action of Belt Feed [/underlined]

The stud on the feed lever is engaged in the cam grooves on the top of the Breach Block and as the B.B. moves to the rear the feed lever is rotated on its axis. The nose of the feed lever is engaged in the recess in the feed slide & moves the slide across the belt. The feed pawl rides over the round held by the retaining pawl and by the action of the feed pawl spring engages the round ready for feeding. During the whole of this action the belt is prevented from leaving the gun by the retaining pawls & spring

8/ [underlined] Second action of Belt feed [/underlined]

As the B.B. moves forward the stud on the feed lever moves in the cam grooves and rotates the feed lever, this causes the feed [deleted] [slide] [/deleted] [inserted] pawl [/inserted] to feed in the belt

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so that a live round is brought against the cartridge stop During this movement the retaining pawl & spring are depressed by the next live round and then under pressure from the spring the pawl rises and engages behind that round.

10/ [underlined] First Forward action of the transporter [/underlined]

As the B.B. travels forward the transporter plunger rides down the sloping face of the rear cam. until the transporter arm reaches the transporter stop. During this downward movement the live round is brought into line with the chamber & firing pin hole. The round is still supported by the ejector and with continued forward movement of the B.B. the live round feeds into the chamber.

11/ [underlined] Second Forward action of the transporter [/underlined]

When the ejector is brought abreast of the ejector slide clearances in the B.E. the transporter plunger starts to side [sic] up the transporter front cam. This causes the transporter to rise and so lifts

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the ejector clear of the round. The ejector being forced outwards by the contour of the case. When clear of the round the the [sic] ejector spring returns the ejector to its normal position. As the transporter reaches its fully forward (movement) or position the claw rides over the rim of the live round in the belt and under pressure from the transporter guide spring engages in the front of it. At the same time the ejector, under the influence of its spring, engages the case of the round ready to support it when later it is withdrawn from the belt In this position the nose of the ejector rests on the top of the ejector clearance on the barrel.

12/ [underlined] Forward rotating action of the Accelerator [/underlined]

When the [indecipherable word] on the B.B. stricks [sic] the horns of the accelerator the latter is rotated forwards. The accelerator ramp becomes disengaged from the B.E. “T” piece and the B. & B.E. are thus free to be driven forward by the B. return spring

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9/ [underlined] Return of the Cocking Lever [/underlined]

During the forward travel of the B.B. the tail of the C.L. engages in the C.L. bracket & rotates the C.L. The rotation re-sets the lever for cocking engages the [indecipherable word] of the sear and firing pin and at the same time gives clearance for the firing pin to travel forward when released.

13/ [underlined] Locking of the Breech Block [/underlined]

As the B. and B.E. moves forward under the influence of the B. return spring the B.E. moves away from the prongs of the lock frame This leaves the L.P free to move upwards when the B.B is home and the B. fully closed. The locking piece being forced upwards by the slope of the L.P. cam it enters the L.P. recess on the B.B. and so locks the B.B. to the B. and B.E.

14/ [underlined] The operation of the sear gear. [/underlined]

On ceasing to operate the controls the rear sear lever is released allowing the rear sear to rise Thus on the backward movement of the B.B. obtained as

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the result of the [deleted] explosion [/deleted] [inserted] recoil [/inserted] the rear [deleted word] of the B.B. depresses the rear sear which is then forced upwards when clear of the [deleted word] bent. [inserted] [indecipherable word] [deleted] On [/deleted] the B.B. being forced forward by the return spring its forward [inserted] movement [/inserted] is [inserted] assisted [/inserted] arrested by the bent engaging the rear sear. The shock of the engagement between the B.B. & sear is absorbed by the buffer spring should the B.B. strike the rear sear before it has fully risen resulting in a partial engagement of the bents. As the rear sear is carried forward in this low position, a projection striker on inclined ramp and forces the bent into full engagement.

Firing of Cartridge

When the B.B. is right forward the lower eng of the Sear is brought into line with the first safe plunger which strikes the sear and drives it inward The sear bent disengages from the F/P Bent The firing pin is carried forward by its spring Thus firing the cartridge

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BROWNING STOPPAGES

[a] NO [b] IMMEDIATE ACTION [c] RESULT [d] CAUSE [e] PREVENTION & SUBSEQUENT REMEDY

[a] 1/ [b] cock & fire gun, watch belt. If feed takes place [c] The Gun fires. Gun does not fire [d] misfire due to defective round Defective firing pin or spring Defective fire & control mechanism [e] NIL. unload change Breech Block Examine & test Fire & control mechanism

[b] If feed doesn’t take place raise breech cover & examine feedway [c] – [d] 1/ Defective feed pawl spring [e] change defective part.
[d] 2/ Defective return [inserted] retaining [/inserted] pawl spring [e] change defective part.
[d] 3/ Defective Transporter claw [e] change defective part.
[d] 4/ Misfire due to belt jamming in feedway. [e] Correct belt filling

[a] 2/ [b] cock & fire gun [c] Gun doesn’t fire
[d] cross feed due to cartridge jamming feedway [e] correct feeding & positioning of cartridge in belt.
[d] Empty link jamming feedway [e] correct feeding & positioning of cartridge in belt.

[b] Raise the breech cover, adjust the belt, cock & fire. [c] The gun does not fire second time & repeats stoppage. [d] 1/ Separated case [e] 1/ unload & use clearing plug, check for correct breeching up
[d] 2/ Defective Transporter plunger or spring [e] 2/ change breech block

[a] 3/ [b] cock & fire [c] Gun fires. [d] Insufficient recoil due to defective cartridge [e] NIL.
[d] Excessive friction [symbol] [e] Correct maintenance

[c] Gun repeats Stoppage. [d] Defective ejector [e] change breech block.
[d] Defective breech block [e] change breech block.

A defective B.R spring. T.G.S. a bent as damaged R.S. [indecipherable word] Rod a distorted of bent [indecipherable words] may cause a stoppage in various positions

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[inserted] adjusting of cartridge head Space [/inserted]

BREECHING UP.

Breeching up is the correct positioning of the breech & of the barrel in relation to the front of the B.B. when the L.P. is fully engaged in the locking recess. It is of the greatest importance and must be done very carefully if the gun is to work efficiently.

Assuming the gun to be fully assembled the following is the sequence of operations

1/ See that gun is not loaded
2/ Raise breech cover
3/ Remove back plate & Return Spring
4/ Remove Cocking Stud & withdraw B.B.
5/ Remove the Transporter switch plate, plunger & spring cocking lever & axis pin from B.B.
6/ Withdraw the re-coiling portions until the locking notches are clear of the breech casing
7/ Remove L.F. from B.E
8/ Disengage Barrel L. Spring & rest spring on lower side of B.E.
9/ Unscrew the barrel slightly
10/ Assemble the B.B., less components, to the B.E Turn the assembly upside down

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and ensure that the L.P. is fully engaged in the L.P. recess.
11/ Hold the L.P. in full engagement carefully screwing the barrel until the breech end is felt to bear against the front of the B.B.
12/ Engage the B.L.S. in the adjacent locking notch. If no notch is coincident unscrew one notch.

N.B.
The Locking spring must not be deformed to obtain engagement.

13/
Push the assembly fully home in the gun until the front end of the B.E. bears against the trunion [sic] block.
14/ Hold the B.E firmly in this position and test for fore & aft movements of the B.B. This movement should not be confused with premissable [sic] lateral & vertical movement.
15/ If fore & aft movement is present withdraw the assembly & screw up the barrel one notch.
16/ Re- test assembly as in (14) and repeat (15) until all fore & aft movement has been eliminated

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17/ Test for over breeching by placing the assembly in gun and pushing fully home. only a normal pressure should be necessary to do this If the locking notches are visible between the B.E & T.B. the gun is over breeched. (i.e.) The locking piece cannot rise into full engagement.

Stripping of Browning for cleaning.

1/ Ensure the gun is unloaded. B.B. in forward position.
2/ Remove Flash eliminator
3/ Remove Back plate
4/ Remove Return Spring & Rod
5/ Pull back B.B. withdraw cocking stud & Remove B.B.
6/ Disengage lock frame retainer plunger & withdraw lock frame B. & B.E. If fitted with rear Sear release unit it will be removed during this operation
7/ Press forward on horns of accelerator and disengage the B. from the B.E.
8/ Raise the barrel locking spring and

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support on the lower face of B.E. Unscrew & remove barrel.
9/ Remove Barel L Spring.
10/ Push out L.P. pin & Remove L.P.

To re-assemble reverse the forgoing procedure ensuring that:-

a/ The firing pin clearance groove is upermost [sic] & that the chamfered edges of the L.P. are forward.
b/ That correct Breeching up is carried out before assembling.
c/ That when assembling the B. B.E & L.F. to the gun body that the rear sear release unit is engaged when the L.F. is about one inch from being fully home. Also that the rear sear is depressed in order to clear the rear sear from the bottom plate.
d/ That the sear is assembled in the B.B. on the same side as the fire & safe mechanism
e/ That the cocking stud is assembled on the opposite side to the F & S.
f/ That the firing pin is cocked &

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Cocking lever forward when re placing Breech Block.

[underlined] N.B. [/underlined]

THE BREECH COVER MUST NOT BE CLOSED UNTIL BREECH BLOCK IS RIGHT FORWARD.

Stripping of Component Parts.

BREECH BLOCK.

1/ Rotate Cocking lever & fire firing Pin
2/ Raise Transporter & withdraw
3/ Remove Switch plate & Plunger
4/ Remove Cocking lever axis pin & Cocking lever
5/ Bring Sear Spring Retainer keeper to central position & push out from underside of B.B.
6/ Remove sear spring retainer taking care not to lose Sear Spring. Remove Sear Spring
7/ Remove sear retainer & sear.
8/ Take out Firing Pin

To Re-assemble reverse above and check by Cocking & Firing

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Browning. Safety Devices

1/ Breech Block must be right forward before gun can be fired

2/ Breech Block is locked before it reaches its most forward position

3/ Breech Block is locked for 5/16” in its backward movement to allow bulk of gases [sic] to escape.

4/ If the sear is accidentally released the cocking lever takes the tension of the Firing Pin Spring

5/ Breech Block stays to the rear due to the action of the Rear Sear.

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7/ Clean inside of breech casing and clean and oil the working parts & surfaces.
8/ Check the correct functioning of the gun if exchanges have been made.
9/ Check the security of gun and mountings
10/ Check empty cartridge case chute and link chute for security & correct alignment
11/ Examine and clean Reflector sight
12/ Enter up the Guns ‘History Sheet’

c/ After flight if firing has taken place

1/ Ensure gun is unloaded.
2/ Remove gun & take to armoury for cleaning.
3/ Strip & examine gun for burrs, wear, damage
4/ Lightly oil all parts & Re-assemble.
5/ Enter up all rounds fired in gun History sheet.

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A/ Operation before flight when firing is to take place.

1/ Inspect the gun attachments & mountings for security
2/ Ensure that the flash eliminator and muzzle attachment are secure.
3/ Clean & dry base.
4/ Clean & oil the moving parts & working surfaces.
5/ Test the fire & safe mechanisms rear sear release.
6/ Check the correct functioning of the gun using drill cartridges in belt
7/ Inspect the ammunition box, empty cartridge case chute & link chute for security & correct adjustment
8/ Check the sights for security & correct alignment & in the case of reflector sight for continuity of [indecipherable word]

B/ Operation between flights when firing has taken place

1/ Ensure that the gun is unloaded.
2/ Empty the spent cartridge container
3/ Re-fill ammunition tanks
4/ Obtain firers report & if necessary make exchange
5/ Remove Flash Eliminator & clean any carbon [indecipherable word]
6/ Clean the base of gun using simple pull through and flannelette

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VICKERS GAS OPERATED .303 GUN

[underlined] General Description [/underlined]

Weight 20 lbs. Overal [sic] Length 40 inches.
Length of Barrel 20 in. Left hand Turning 1 in 10in.
Base .303. Magazine 60 or 100 rounds
Rate of Fire 950 rounds per min. (approx)

[underlined] The Gun is divided into two parts or groups [/underlined]
a/ Stationary Parts. B/ Recoiling Parts.

[underlined] Stationary Parts consist of :- [/underlined]
1/ Barrel Group. 2/ Body & Gas cylinders
3/ Return Spring & Rod. 4/ Deflector & Deflector Bag Grip
5/ Body Extension & Spare Grip 6/ Magazine

[underlined] Recoiling Parts consist of [/underlined] :-
1/ Piston Rod 2/ Breech Block

First action/

[underlined] Cocking by hand [/underlined]
On the cocking handle being pulled to the rear the cocking lug being engaged in the slot in the Piston Rod draws the Piston & Breech Block to the rear. This movement continues until the bent on the Piston Rod is engaged by the sear, at the same time the Return Springs are compressed.

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V.G.O.

Forward movement.

[underlined] The Release of the Sear. [/underlined]

When the Trigger is pressed the Trigger Rod is forced forwards & compresses the T.R. Spring the forked end of the T.R. being engaged against the lower arm of the Sear rotates the Sear on its axis compressing the sear Spring & withdrawing the nose of the sear from the Bent on the P. Meanwhile has the Lugs on the T.R. moves forward [inserted] and [/inserted] the Sear catch is rotated under the action of its Spring the arms engaging over the Stop on the Sear. When the nose of the Sear is disengaged from the Bent on the P.R. the P.R. is forced forward under the influence of the Return Spring carrying with it the Breech Block.

[underlined] Feed of Round into Chamber [/underlined]


Has [sic] the B.B. moves forward the Feed Piece engages the cartridge held in the lips of the Magazine forcing the bullet end of the cartridge under the bullet Guide guiding the bullet into the Chamber. At the same time

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the base of the cartridge is forced downwards onto the face of the B.B. where it is engaged. The final movement of the B.B. forces the cartridge fully home into the Chamber.

[underlined] Locking of the Breech Block [/underlined]

When the B.B. reaches the end of its forward movement the P.R. continues to move forward & the Locking Cam on the sear of the P.R. bears against the corresponding cam on the rear of the B.B. forcing the rear of the B.B. up until it engages in front of the Locking Shoulders in Body. The P.R. still continues to move forward and the Horizontal surface of the sear bears against the corresponding position on the underside of the B.B. Thus returning the B.B. in its Locked Position.

[underlined] Firing of Cartridge [/underlined]

During its final forward movement the front of the P.R. projection (hammer) strikes the firing pin forcing it forward & compressing the Firing Spring Pin

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V.G.O.

Backward Movement

[underlined] Action of Gases [/underlined]

When the cartridge is fired the Cordite turns to Gases & forces the bullet up the Barrel. After the bullet has passed the Gas Vent in the barrel the Gases pass through the Gas Vent into the Gas Block. These Gases are deflected into the Gas Cylinder where they impinge on the head of the P.R. driving the P.R. to the rear & compressing the Return Spring[inserted]s [/inserted] Backward movement of the Piston
[underlined] Rod & the unlocking of the Breech [/underlined][inserted] Block [/inserted]

As the P.R. is forced to the sear the front of the P.R. projection is disengaged from the Firing Pin, at this time the Horizontal surface of the rear of the P.R. still [indecipherable word] against the Horizontal surface of the Breech B. ensuring that the B.B. remains in the locked position until the Gases have escaped from the Chamber. As the P.R. moves further to the rear the unlocking cam on

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V.G.O.

the P.R. bears against the corresponding Cam on the B.B. forcing the B.B. down and the Locking Shoulders out of engagement with body Locking Shoulders. The P.R. now carries the B.B. to the rear until the P.R. is brought to rest against the Buffers on the Body Extension.

[underlined] Extraction & Ejection [/underlined]

As the B.B. moves to the rear the claw of the extractor being engaged with the rim of the empty cartridge case draws the empty case to the rear. The B.B. continues rearward until the tail of the ejector is struck by the ejector cam causing the ejector to rotate on its axis and the nose of the ejector strikes the base of the empty case forcing it through the ejector opening into the deflector bag.

[underlined] Action of the Feed Piece [/underlined]

As the B.B. moves to the rear the Feed Piece is forced down by the the [sic] live round held in the Magazine When [deleted] passed [/deleted] past the live round

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V.G.O.

the F Piece is returned to its normal position by the F Piece Spring

[underlined] Engagement of the Sear. [/underlined]

When the trigger is released the trigger & trigger Rod are returned to their normal Position by the T. Rod Spring thus forcing the forked end of T.R. from the lower arms of the Sear. The Sear is still unable to rise until the T.R has almost reached the limit of its backward movement when the Lugs on the T.R. bears against the Sear Catch rotating it to the rear & disengaging the arms of the sear catch from the Step on the Sear. The Sear is now forced up into position by the Sear Spring & engages the Bent on the P.R. The shock of the engagement between the Sear & the Bent on the P.R. is absorbed by the Buffer Spring through the Sear lever & the Sear Spring Plunger. In the event of only partial engagement of the sear the sear is forced

[page break]

forward its underside bearing against the Sear Stop this action forces the Sear to Rise into full engagement with the bent on the P.R.

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Machine Gun Maintenance

Powder Fouling:-

Forms as a hard scale on the surface. as in the flash eliminator, barrel. Its [underlined] Caused [/underlined] by deposits from the burning of the propellant (cordite, neonite as nitro-cellulose.

Removal:- Soak in Type ‘A’ cleaning oil for 10 mins (approx.) clean with 4” x 2” as is necessary 30-40 strands of brass wise 26 gauge soaked in Type A cleaning oil

Chemical Fouling:-

Is caused by decomposition of the cap compound and produces a salt like substance [inserted] which [/inserted] collect moisture from the air. This acts on the barrel like sea water on a metal ship
Removal:- as for Powder Fouling

Metallic Fouling:-

Is caused by nickel deposits from the bullet envelope on the grooves & lands. Detected by use of .301 gauge as visual checking on Group C & F inspection
Removed by:- Two tablets of K.N.N.S

[page break]

dissolved in 40 P.P. of liquid ammonia at a specific gravity of .95 for a period of (approx.) 30 min. If nickel is present the liquid will appear as a deep blue or bluish green liquid. Repeat process until clear or nearly clear liquid appears after treatment with solution. Dry base & clean with Type A oil Solution
28 Tablets. 40.c.c. { 50% 88 SG ammonia/50% water
1 pint of mixture.

Metallic Fouling. Copper. 20mm. Gun
Detected by use of 20.02 mm. gauge at Group F inspection (3 days or 600 Rounds)
Removed by using wire brush if fouling is slight

Copper Solvent.
1 1/4 pints of Ammonia Pes sulphate.
5 pints .88 S.g. Ammonia
4 pints of water.
Leave for 3 hours Re-check repeat if necessary.

[page break]

Gauges.

.303 Test for metallic fouling Barrel end
.307 Test for Barrel wear must not pass right thro’
.308 Test for [indecipherable word] wear at muzzle end. (bell mouth)
Plug lead No 2.
.6” Reject for use with incendiary ammo
1.5” Reject for air operational use
3.0” Reject for air use training station
4.5” Reject for ground use.
After every 1000 rounds Test bore of gun by firing 10 round on the 25 yrd range. If bullet pattern exceeds 7” x 6” barrel is u/s for all purposes.
.064 Test for cartridge Rim Guides used in conjunction with .003 feeler gauge.
.074 Should not enter.
.050 Firing pin shouldn’t pass over
.058 Should pass over firing pin
.076 test for [indecipherable word] of firing pin

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STOPPAGES V.G.O.

[A] NO. [B] Immediate Action [C] Result [D] Cause

[A] 1 [B] Pull back cocking handle push forward fire & watch toppled [C] 1/ Gun fires – 2/ Top plate revolves – 3/ Top plate does not revolve – 4/ Gun fires single shot [D] 1/ Misfire – 2/ Probable broken firing pin or spring – 3/ a/ Empty magazine, b/ Defective magazine, c/ Broken feed piece or spring – 4/ [circled a] Insufficient tension on magazine spring, [circled b] Dirty gas block, [circled c] Excessive friction

[A] 2 [B] pull back C.H. push forward. Remove & inspect Mag. look in body & chamber [C] 1/ Round half forward in magazine – 2/ Empty case on face of Breech Block – 3/ Round half forward in chamber – 4/ Empty case in body or ejector opening [D] 1/ Round jammed in lips of magazine – 2/ Broken ejector, 3/ Separated case, 4/ Full deflector Bag.

[A] 3/ [B] pull back C.H. push forward. Remove & inspect Mag. look in body & chamber [C] 1/ No round in body or Chamber – 2/ Live Round in body – 3/ Empty case in chamber [D] 1/ Round jammed in lips of mag – 2/ Misfeed – 3/ Broken extractor

The main stoppages are mainly due to defective Ammunition Defective magazine or defective parts of the Breech Block

Rear end of the piston viewed thro’ the cocking handle slot as determined by pulling back the cocking handle until the cocking lug [deleted] slot [/deleted] engages the C.H. lug slot will indicate the [indecipherable word] stoppage [circled 1] cocking handle fully forward. [circled 2] CH below as in front of Rear Mag catch [circled 3] C.H. to rear of Rear Mag. Catch.

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[underlined] SIGHTING [/underlined]

[underlined] Definitions [/underlined] :-

[underlined] Muzzle Velocity:- [/underlined] is the velocity imparted to the bullet by the charge 2440 ft p.s.

[inserted] 2220 ft p.s. [/inserted] [underlined] Average Velocity:- [/underlined] is the average velocity of the bullet over a particular range

[underlined] Point of Intersection:- [/underlined] is that point were [sic] the bullet and target meet

[underlined] Deflection:- [/underlined] Is the distance moved by the [deleted] bull [/deleted] target during the flight of the bullet

[underlined] Angle of Deflection [/underlined]:- Is the angle formed by a line through the axis of the barrel to the firers eye and aligned from the firers eye to the target

[underlined] Trajectory [/underlined]:- Is the actual path of the bullet

[underlined] Cone of Fire:- [/underlined] is that point or position of space that contains all the trajectories of all the bullets fired

[Underlined] Relative Speed [/underlined]:- is the speed of one object in relation to another one as both being in motion

[underlined] Point of Harmonisation:- [/underlined] Is that point at which the line of sight

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intersects the trajectory of the bullet under certain specified conditions

[underlined] Construction of 50 mph Ring Sight [/underlined]

[equations, diagram and calculations]

Relative Speed Sighting

When firing a free gun from a/c at another one there are two main factors which influence the point of aim.

A/ The velocity of the target a/c.
B/ The movement imparted to the bullet

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by the velocity of the gunners a/c. In relative speed sighting these two factors are combined and only the resultant considered (ie). The relative velocity of the target

[underlined] Principals of Relative Sighting [/underlined]

In relative speed sighting the gunner is not concerned with the actual velocity of the target but only with its apparent velocity relative to his own a/c. His only concern is with the speed & direction with which the target appears to move across the ring of his sights

In short the gunner allows only for what he sees The direction of the apparent motion of the target must always be made to pass through the centre of the ring while the amount of deflection to be allowed is to be determined by the apparent speed of the target across the ring.

The 50 mph Ring sight [indecipherable word] at 20 ft for every 100 yds

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Method of using Ring Sight

1/ Identify the target
2/ Place the centre of sight on target hold the sight steady & watch which way the target appears to move across the ring and at the same time estimate its apparent speed
3/ Move the sight along the line of apparent motion overtaking overtaking [sic] the target & position the target so that it appears to move through the centre of the ring & at the same time make the correct deflection allowance for the estimated apparent speed Fire a burst & repeat the whole procedure.

[diagrams]

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Reflector Sight

Free gun reflector sight Mrk. IIIA.

General Description

The sight consists essentially of a flat clear glass screen inclined at an angle of 45° through which the target is seen The light from the graticule illuminated by a double filament lamp is projected through a lens system onto this screen from below and at the same time is reflected at right angles in the direction of the gunners eye. The image of the graticule is projected to infinity & always appears superimposed on any target in the line of sight

The sight may be used on 12 or 24 volt circuit & is fitted with a dimmer switch for use at night. The hood which is adjusted for harmonizing purposes is provided with a tinted glass screen for use against a bright background

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Advantages of Reflector Sight

1/ The sight base is flexible and sideways and vertical movement of the eye – within certain limits – is permissible. As long as the complete graticule can be seen the sight may be considered correct.

2/ The bead is fixed in the centre of the ring so removing any possibility of error due to the none alignment of the sight

3/ The Graticule always appears superimposed on the target so the eye hasn’t to try and focus itself on near & far objects at the same time

4/ The sight may be used effectively at night time

5/ the Gunner uses both eyes so giving him wider range of vision & also relieving eye strain

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6/ the sight may be fitted in the most convenient position in the turret & is also free from shock

Disadvantages

1/ The sight is an electrical device and is liable to electrical failure

Precautions

1/ See that the correct bulb is fitted and fitted the correct way and make sure that terminals marked A. & B. are connected [sic] for 12 volt system & left out for 24 volt system

2/ See that there are no signs of blackening on top of bulb.

3/ See that a supply of spare bulbs is carried

4/ Test the sight for continuity of circuit & the dimmer switch for correct functioning

5/ Keep Glass surface clean & free from scratches

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6/ Make sure the sight is securely mounted & correctly harmonized

7/ Don’t burn lamp any longer than necessary.
N.B. Life of bulb is approx. 100 burning hours when free from gun shock and 1500 rounds when under gun shock

Bullet Trail.

[diagram]

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Factors Effecting the Amount of bullet Trail

1/ Speed of Gunners aircraft

2/ Range.

3/ Altitude

4/ Direction of Fire

Allowance for Bullet Trail. Beam Shot. Speed of G.A/C. Range

200 mph. [a] 200yds [b] 300yds [c] 400yds
[a] 8 ft [b] 16 ft [c] 24 ft
[a] 25 mph [b] 30 mph [c] 35 mph

300mph. [a] 200yds [b] 300yds [c] 400yds
[a] 12 ft [b] 24 ft [c] 36 ft
[a] 40 mph [b] 45 mph [c] 50 mph

The above figures for an altitude of 10,000 ft.

From 90° to 45 full allowance
From 45° to 15 half allowance
From 15° to 0° no allowance

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[underlined] Tracer [/underlined]

Types of tracer in use.

[d] starts to Burn [e] Burn out.
G.I White trace [d] 0 to [e] 300-400 yds
G.II Red trace [d] 0 to [e] 1000-1200 yds
G IV Red trace white top [d] 0 to [e] 600 yds
G V Red trace. [d] 200 to [e] 600 yds

[diagrams]

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[a] RS Method [b] Common [c] Tracer method

[a] Observe the apparent relative speed of E a/c Estimate path of E a/c Make adjustment of Bullet trail
allow for Gravity drop Then position Target in Ring Sight [b] Identify a/c Estimate Range Aim Point Blank [c] [underlined] Continue [/underlined] to aim point blank and fire a sighting burst 10-15 rounds.

Ranges

1/ Point blank. 0 to 150yrds it’s the range at which allowances shooting is discontinued and Rapid point blank aim maintained
2/ Effective Range. 150 – 400 yrd [sic] at this range you have a good chance of destroying enemy. A large amount of ammo may be expended.
3/ Long Range 400 – 600 yrd. [sic] use limited amount of ammo. Main object to upset aim of enemy a/c and on the off chance of a hit
4/ Very long Range.
Is that range at which under the gunnery leaders direction a very limited amount of Ammo may be expended.

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VECTORS

A vector is a line of a certain length in a certain direction

Triangle of Velocity

Vector Problems.

1/ Draw a line to represent the e/a/c. speed & direction
2/ From the end of the enemy speed. draw a line to represent the speed of G.a/c in reverse.
3/ Complete the triangle, put in all arrows. This side of the triangle is the True Relative Speed.
4/ Draw in the line of sight
5/ Draw a line from the line of sight @ sight angles to it to the end of the line of True R. Speed.
This line is the apparent R. Speed.
The length of the line indicates the magnitude of the speed & the direction is [underlined] always [/underlined] from the line of sight to the true relative Speed

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Sensitive No 252

[diagrams]

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[underlined] AMMUNITION [/underlined]

[underlined] Types [/underlined]

[drawings & notes]

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[diagrams]

[inverted Calculations]

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Errors of Ring & Bead Sight

1/ Incorrect head position. If the sight is to be correct the gunner must maintain a sight base of 18”-19”, If, however his head is too near or too far away, an incorrect line of sight will be obtained as will be seen in the following diagram.

[diagram]

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Maintenance of Reflector Gun sight

1/ See that the correct bulb is fitted & filled the correct way, and make sure that terminals marked A & B are connected for 12 volt system & left open for 24 Volt system.

2/ See that there are no signs of blackening on top of bulb.

3/ See that a supply of serviceable bulbs are carried

4/ Test the sight for continuity of circuit & the dimmer switch for correct functioning

5/ Keep glass surfaces clean, dry & free from scratches

6/ Make sure the sight is securely mounted & correctly harmonised

N.B. Change bulb at the end of 30 [underlined] hrs [/underlined]

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[underlined] Definitions [/underlined]

1/ [underlined] Muzzle Velocity [/underlined] is the velocity imparted to the bullet by the charge. 2440 ft per sec.

2/ [underlined] Average Velocity [/underlined] is the average velocity of the bullet over a particular range. 2200 F.P.S.

3/ [underlined] Point of Intersection [/underlined] is that point were [sic] the bullet & target meet.

4/ [underlined] Deflection [/underlined] Is the distance moved by the target during the time of flight of the bullet.

5/ [underlined] Angle of Deflection [/underlined] Is the angle formed by a line through the axis of the barrel to the firers eye and aligned [sic] from the fixers eye to the target

6/ [underlined] Trajectory. [/underlined] Is the actual path of the Bullet.

7/ [underlined] Cone of Fire [/underlined] Is that portion of space that contains all the trajectories of all the bullets

8/ [underlined] Relative Speed [/underlined] Is the speed of one object in relation to another, one or both being in motion.

9/ [underlined] Point of Harmonisation [/underlined] Is that point at which the line of sight intersects the trajectory of the bullet under certain specified conditions

10/ [underlined] Line of Sight [/underlined] Is the straight line from the firers eye thro’ the sight to the target

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Construction of 50 M.P.H. Relative Speed sight Ring

[Notes, diagram & calculations]

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Range Estimation. Wing Span. 36 [missing word]

A/C. Filling Ring 1/2 w/s. add 0 180[symbol] Range
A/C. 3/4 Filling Ring 2/3 w/s add 0 240[symbol] Range
A/C. 2/3 Filling Ring 3/4 w/s add 0 270[symbol] Range
A/C. 1/2 Filling Ring w/s add 0 360[symbol] Range
A/C. 1/3 Filling Ring 1 1/2 w/s add 0 540[symbol] Range
A/C 1/4 Filling Ring 2 w/s add 0 720[symbol] Range

[table]

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[diagram]

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HARMONIZATION
[underlined] Single Gun [/underlined]

[diagram]

[calculations]

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TURRETS.

Frazer Nash turret:-

Filling of System.

1/ See that the Gun ram is fully closed.

2/ Slacken union at Engine Driven Pump.

3/ Remove filler cup from Recuperator and with a gauze lined funnel fill top reservoir (100% Anti Freezing oil) at the same time using hand pump

N.B. Do not exaust [sic] all the oil in the reservoir before re-filling as you will only pump air into the system

4/ Continue to fill & pump until clear oil flows from slackend [sic] union nuts. Tighten unions.

5/ Continue to fill & pump until the recuperator spindle protrudes [underlined] 4” [/underlined], except in the case of a retractable under turret in which case spindle should protrude [underlined] 3in [/underlined] Fill reservoir to one inch of the top in all cases.

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6/ Operate controls in all motions so as to fill remaining pipes and units with Gun ram fully closed Top up at recuperator.

BLEEDING Power. Method

1/ Start up engine & as soon as warm run at approx. 1000 R.P.M.

2/ Open bleed screw at top of Gun ram body. Open Master valve, set control to extended ram position. Close bleed screw when clear oil flows.

3/ Open bleed screw at top of gun ram piston rod. Open Master valve; set controls to ram closed position. Close bleed screw when clear oil flows.

4/ Detach [inserted] Rear [/inserted] gear release from guns, open bleed screws. Open master valve. press trigger Close bleed screw when clear oil flows Attach [inserted] Rear [/inserted] sear releases to guns & with gun ram closed top up at recuperator.

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BLEEDING: Static Method

1/ Inspect system for leaks.

2/ Pump recuperator spindle to its fullest height to expel any air which may have gathered under the plunger.

3/ Open bleed screw at top of gun ram body
Open Master Valve, set controls to extended ram position Close bleed screw when clear oil flows.

4/ Open bleed screw at top of gun ram piston rod. Open Master Valve, Set controls to ram closed position. Close bleed screw when clear oil flows

5/ Bleed sear release also but do not open Master Valve and do not press trigger. With gun ram closed top up at recuperator.

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FUNCTIONS OF RECUPERATOR

1/ Means of filling System

2/ Maintenance of Static Pressure of 16 lbs per Sq in. when system is at rest

3/ Maintains Static Pressure of 12-20 lbs per sq in. when System is working.

4/ Acts as a chamber of variable Volume.

5/ Compensates temperature variations

Faults of F.N.T.

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Frazer Nash Turret

For simplicity of instruction in both mechanism & filling & bleeding of the System it is advisable to take the components in the following order:-

1/ Engine Driven Pump.
2/ Relief Valve.
3/ Recuperator
4/ Rotating Service Joint
5/ Valve Box.
6/ Vane Oil Motor.
7/ Hydraulic Ram.

Engine Driven Pump.

Consists of a cast metal body having two ports of unequal bore the larger being the suction or inlet, the pressure port has a lip which prevents turbulence inside the pump so as to present excessive friction on the pipe walls which if allowed would effect [sic] the efficiency of the pump.
Inside the body are two pinions in mesh with each other. One pinion is

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attached to a splined shaft which is attached to the engine this is known as the driving pinion. The driven pinion is supported on two short trunions [sic]. Each turret system requires a pump in which case two pumps are mounted together & termed ‘Ganged’ pumps. The pumps are separated by a partition & a gland surrounding the driven shaft. If this partition or gland broke down through fracture or wear oil could be pumped from one system to the other and would be indicated by the position of the ‘Indicator Spindle’ of the recuperator.

The Relief Valve.

Consists of a metal casting through which runs the main pressure and main exhaust pipe lines attaching there is a smaller passage into which is fitted a steel seating. The Valve itself is made of steel & is known as a ‘Poppet’ valve, the valve is kept on its seating by means of a

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guide & spring. The spring weight is governed by this general rule:-

The weight of the spring plus the weight of the back pressure in the exhaust pipe line equals the forward pressure in the main pressure pipe line at that point.

Recuperator

1/ Consists of a metal cylinder divided into two compartments by a fixed seal. The top compartment is named the reservoir & has a filler hole & cap at the top and a hole near the bottom to allow communication with the hand pump

2/ The lower compartment is named the Chamber of Variable Volume, inside it has a spring loaded piston the spindle of which protrudes through the top of the recuperator and is known as the ‘Indicator Spindle’

3/ Secured to the bottom is the base running through which are the pressure & main exhaust passages. The main pressure enters & leaves

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immediately & does not normally communicate with the C of V.V. the main exhaust, however, does communicate with the C of V.V. & it is by this means that the Recuperator does its work.

4/ Secured to the body as barrel of the recuperator by a metal strap is the hand pump. This consists of a cylinder & plunger. the cylinder has a hole near the top and its exit may be closed by a spring loaded non-return ball valve. The plunger has a series of holes drilled from a shoulder which converge on a central passage, this passage may be closed by a spring loaded non-return [inserted] ball [/inserted] valve on the base of the plunger is another series of holes which if the ball valve was unseated would communicate with the top holes.

Drilled through the walls of the recuperator are two series of holes which in conjunction with a channel in the strap from the transfer Ports their object is to prevent over filling

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the system & to allow the escape of air.

[underlined] NOTE. [/underlined] In the case of Poppet valves & spring loaded non-return ball valves should the valves become unseated due to grit or foreign matter or should the seating become scored as the Spring weaken or break the efficiency of the valve will be greatly impaired.

Function of the Recuperator

1/ As a means of filling & bleeding the System.

2/ To maintain a static pressure of (approx.) 16 lbs. per sq. in throughout the whole system when the system is at rest so as to prevent the entry of air.

3/ To maintain a pressure of between 12 – 20 lbs per. sq. in. on the exhaust side of the system when the turret is in operation so as to ensure a constant supply of liquid to the suction side of the pump & to prevent ‘wire pulling’ and Cavitation

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4/ To allow for Variation in the capacity of the hydraulic ram due to its unbalanced piston which means that more oil will enter the ram than will leave it when the ram is being extended & vice-versa.

5/ To allow for variation in the temperature of the liquid

Rotating Service Joint

There are two types. The fully R.S.J. & the Partially rotating S.J. They are situated in the vertical axis of the turret either above (Top entry) or below (bottom entry) They in no way support the weight of the turret

The fully R.S.J. conveys into the turret oil, electricity & oxygen [deleted] also [/deleted] oil to power the turret, electricity to heat the guns, gunners clothing to light the sights & Turret lamps & for inter com. The oxygen for the gunners use a [sic] high altitudes

The partially R.S.J. conveys oil only electricity & oxygen being laid in by flex & tubing

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Valve Box.

In the valve box there are three valves The Master Valve Elevation & Depression Valve & Rotation Valve. each valve moves in a sleeve. this sleeve is perforated to give communications with passages & ports in the body. The valves are of the piston type. The master valve having three lands & two positions & one re-positioning spring The functional valves have two lands, three positions & two centralising springs each valve has a spindle which is conected [sic] to the rocking handles by means of linkage On the Rocking Handles are the M.V. levers which must be depressed before the turret can be operated. To rotate the turret the R.H.s are turned on their vertical axis in the same manner as steering a [deleted] by [/deleted] bicycle To elevate or depress the guns the R.Hs are twisted on their horizontal axis in the same manner as the twist grips on a motor bike, the amount of movement given to

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the R.H. controls the amount of movement of the functional valves which in turn controls the rate of flow of liquid and the speed of the turret movement

Vane Oil Motor

Consists of two main parts. The Rotar & the Statar [sic]. The Rotar is drum shaped & has six groves [sic] housing six vanes, drilled (vertically) transversally through the rotar are six holes housing six pins whose object is to keep the vanes. equi distant there are two end plates one of which carries a splined shaft on to which is secured the turret driving pinion. Each end plate has six “L” shaped holes the object of which is to prevent cushioning of liquid behind the vanes & also to preserve a static balance on the vanes The Rotar is mounted eccentrically to the Statar The Statar is a steel sleeve pressed into the body [deleted] of the [/deleted] and being ground out on a (pola-radii) There are two parts of the statar which form a true circle the one between

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the parts of the body being known as the working surface, on either side of the working surface are two series of holes which communicate with the ports of the body by means of ducts

Hydraulic Ram.

Consists of two main parts a cylinder and a piston, the cylinder has a port at the bottom and one at the top for the entry & exit of liquid. Near the top is a bleed screw for removing air from the system at the top are the means of adjusting the length of the piston store. The piston is of the unbalanced type, it has two washers opposed to each other to take the thrust from either direction. The shaft carries a floating sleeve which is part of the adjustment, the shaft is hollow & has a bleed screw near the top for removing air. At the top there is a hole to accept a pin to secure a piston to the gun arm.

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Vokes [deleted] Volkes [/deleted] Filter

Consists of a cap an inner and outer canister, the cap is secured to the main exhaust pipe line, inside there is a cylinder directly conected with the inlet port. The outlet port communicates directly with the outer canister, secured to the cap by means of a ring is the outer canister which has a drain plug at the bottom and contains a [indecipherable word] spring which is responsible for holding the inner canister against the cylinder of the cap. The inner canister is a perforated brass cylinder with two end plates held together by a screw and winged nut the top [inserted] cover [/inserted] [deleted] [indecipherable words] [/deleted] has a cylinder with a series of holes near the bottom which enter the cylinder of the cap when the filter is assembled, between the end plate & the cylinder is fitted a fibre washer inside the inner canister is a corrugated felt filter reinforced by a course [sic] wire mesh.

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.303. Mk VII.

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[INTERNAL DEMAND AND ISSUE VOUCHER]

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[Answer to Quiz]

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[picture]

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.303 MK VII

[pressure grid]

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[4th WEEK TIMETABLE]

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.303 Mk VII

[points & remarks of Commanding Officer]

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[missing word] ALL INSTRUCTORS.

Copy To:- Chief Instructor.
Chief Gunnery Leader.

Date:- 10th February, 1943.

[BREECHING UP – BROWNING .303 memo]

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[No.29 GROUP UNITS POSTING sheet]

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[folded page]

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.303 MK VII

Cap Composition

[indecipherable words]

Potassium Chlorate

Antimony Sulphoids

[indecipherable word] Powder

[underlined] Sulphor [/underlined] 1% P

[underlined] potassium chlorate [/underlined] [indecipherable word] burning.
[underlined] Antimony sulphate [/underlined] give Body.
[underlined] [indecipherable word] powder [/underlined] [indecipherable word] flame.
[underlined] Sulphor [/underlined] diminishes Violence

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Cap [underlined] Compo [/underlined]

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Range. Standing Orders.

[underlined] Supervision of Firing [/underlined]:-

Firing is only to take place under the supervision of an Officer or Instructor who has to explain all practices to firers prior to commencing fire.

[underlined] Red Flags on Butts [/underlined]:- Before firing a flag 4ft x 3 ft is hoisted on the Butts to indicate that the range is being used & should remain hoisted until firing is completed then remove.

[underlined] Red Flag at Firing Point & Markers Shelter [/underlined]:-
These to be hoisted when markers are present. Until flags are lowered guns must not be loaded.

Safety positions of Guns:-
V.G.O. must have their magazines removed & Guns set at Safe Browning Guns to have rear cover raised & Breech Block to the rear. Firing [missing words] to safe Safety Stops to be [missing words] to mountings so that so that guns [missing words] be traversed or raised any further than is necessary.

Awaiting details must stand clear of firing point & should have [missing word] instruction in aiming with [indecipherable word].

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gun as practical.

[underlined] Issue of Ammunition [/underlined]:- N.C.O. responsible for issue of belts or ammo & magazines to firers when ready to take up position from the firing point, after red flag has been withdrawn or lowered.

Conduct of Practices:- The pupils will wait for the instructor to give orders before firing. The instructor will order the Red Flags on a firing point and markers shelter to be withdrawn or lowered. (On completion) – when practice is completed the instructor will order “unload” immediately whether they have actually finished or not.

When firing V.G.O. the Mag. will be removed & gun cleared. Browning guns unloaded & B.B. to the sear

[indecipherable word] of Guns or Stoppages.
If there should be a stoppage & firer cannot clear with immediate action he will leave the gun with the muzzle pointing towards the butts and report to the instructor. The stoppage to be dealt with at the firing point by qualified personnel. If it cannot be cleared & the gun

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contains a live cartridge move the gun to the rear of the firing point whilst range is in use.

[underlined] Inspection of Targets [/underlined]:- Red flags to be hoisted on firing point after guns cleared as per para ( ) then target will be inspected. Markers to wait for permission before leaving shelter.

[underlined] Gun Cleaning [/underlined]:- Guns will be cleaned at the finish of practice as laid down in the Armament Training Manual. Collection of empty cases & [deleted] emp [/deleted] [indecipherable word] links. Each firer to collect his own & place them in boxes provided. [inserted] The [/inserted] N.C.O. will ensure that this is carried out & that no live rounds are mixed with the fired cases.

[underlined] Carrying Live Rounds [/underlined]:- under no circumstances must live rounds or miss fires be carried on person.

[underlined] Dummy Cartridges [/underlined]:- authorised [indecipherable word] only to be used.

[underlined] Smoking is prohibited [/underlined] on the range.

Locking of Workshop The officer or N.C.O. will be responsible that workshop & target Store are properly locked up

The cease [inserted] fire [/inserted] order [inserted] will be [/inserted] given if any a/c

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attempt to fly over the range.

[underlined] Night Firing [/underlined]:-

Order will be read & signed on the spot were [sic] firing is to take place.

Post Light
Ground . Salt Petra 71%
Surplus 18%
[indecipherable words] 11%
Burns 10 mins (approx.)

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Boulton Paul Turret

For the sake of instructions it is advisable to divide the instructions into 4 parts
1/ Hydraulic 2/ Electrical 3/ Mechanical 4/ Pneumatic
followed by such things as re-arming Gun installation, Harmonization & maintenance

Hydraulic.

Hydraulic Generator or Pump:-

The power which drives the the pump is generated by an engine driven dynamo – supply 1000 watts – this is lead in thro’ the turret by an electric distributor situated on the vertical axis of the turret either above or below, from there it is carried through switches to the electric motor which drives the pump, this motor absorbs 24 amps On the motor armature shaft is a pinion which is the “gun pinion” of an [indecipherable word] gear this consists of three main members:- The Gun Pinion, The Planetary Pinions with

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their carrier or spider & The Planetary Ring which in this case is always fixed The drive is carried thro’ from the gun pinion to the planetary Pinion & carrier giving a reduction in speed of 5 to 3 (approx.) The carrier is attached to the back of cylinders which is caused to rotate. This bank of cylinders has two rows of five each, inside each cylinder is a heavy steel piston which depends on centre fugal force for its movement. Each cylinder has a port at its inner end & is open at its outer end so as to allow the piston to protrude & contact the guide ring There are two guide Rings one for each row of cylinders, they are conected to the control column by means of linkage, each guide ring is set to move at 90° to each other The bank of cylinders embraces our hydraulic distributor. The distributor has four vertical passages each having four holes in the following order [inserted] from top to bottom [/inserted] (1) elongated port either suction or delivery (2) For the relief valve

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(2 for rotation 2 for elevation) elevation 750 lbs per sq in Rotation 1200 per sq in
(3) Inlet valve (4) Pipe lines.

The Sump is the means of filling and carries a reserve supply of liquid its webbing houses the Relief & Inlet Valves

The Hydraulic Motor.

Consists of 3 main parts 1/ The Elliptical Ring 2/ A bank of Cylinders 3/ Hydraulic Distributor

The elliptical has a major & minor axis which breaks the ring into four cams, these [deleted] cames [/deleted] cams being uphill or downhill according to the direction of rotation of the cylinder – There are 6 or 7 cylinders each cylinder containing a hollow piston, at the outer end of the cylinder are two flats which prevent piston rotation At the inner end there are ports to correspond with ports on the hydraulic distributor. The pistons have a spring loaded up thimble inside the object of which is to keep a soft rubber washer up to its work in preventing

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excessive escape of liquid [deleted] passed [/deleted] past the piston, in this it is not completely efficient so that an overflow pipe is necessary to carry the excess back to the sump of the hydraulic generator The outer end of the piston carries two rollers to lesson friction against the elliptical ring. The hydraulic distributor has two ports near the top which correspond with two passages in the body for the entry [deleted] of [/deleted] as exit of liquid these communicate by means of [deleted] a [/deleted] passages by means of four lipped ports drilled on the one plain to correspond with the cylinders, they are set in pairs and open 108° to each other. At the top of the hydraulic distributor is a positioning square which ensures correct register between the inlet & outlet passages and the top ports of the distributor, it also prevents the distributor from moving The pinion attached to the cylinder body is the sun pinion of an epicycle gear which gives a reduction to the turret driving

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pinion. A means is provided for breaking this gear so that the turret can be rotated manually

Pressure Regulator Box.

Its object is to prevent gun sinkage or creep & to provide a hydraulic lock on either side of the ram piston under all conditions of flight also to allow oil to be by-passed from one end of the ram to the other when manually operating the guns.

It consists of two identical sets of of [sic] the following:-

A hollow metal tube with a series of holes drilled through a shoulder held against a poppet valve by means of a spring, the shank of the poppet valve is fluted to permit the passage of oil. This valve is only opened when liquid is leaving the ram at a pressure in excess of 130 lbs per sq. in. In a passage close to the shoulder of the tube is a spring loaded non-return valve which is washed off its seating by the liquid flowing to the ram.

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Drilled thro’ the centre of the box is a passage closed at each end by a ball valve. Bearing against each of these is a fluted needle. Between these is an egg shaped cam operated by the Free & Engage Lever, the cam can be rotated & force the fluted needle outwards & they in turn force the ball valves off their seatings so that oil can be by-passed from the top of the ram to the bottom of the ram cylinder when the guns are moved manually

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[Bullet notes]

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the clock of engagement at the same time.

The ramp on the sear engages sear cam in the trigger mechanism plate & ensures positive engagement of the bents. The sear buffer springs return the buffer slide, Sear slide, sear & B/B to their normal cocked position when the energy is expended.

Safety arrangements

1/ If the B/B is not fully home the locking Piece cannot be lowered into engagement with the locking Shoulder
2/ The unlocking plates cannot move forward independently of the B/B unless L.P. is in full engagement with the locking Shoulder
3/ Positive engagement of the locking piece L.S. is ensured by the final [indecipherable word] in a forward movement of the unlocking plates
4/ Firing Pin which is [indecipherable word] by the [indecipherable word] cannot strike the cap of the cartridge until the locking plates reach the end of this forward travel
5/ The Locking Piece cannot rise out of engagement with the L.S. until they have travelled the [indecipherable word] safety distance thus ensuring
(a) [indecipherable words] of Gases have left the barrel
(b) The firing pin is withdrawn from the FP. hole in case of [indecipherable word] cap allowing the gases to escape

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4/

far in the backward movement for the ejector [indecipherable word] to engage on the base of the round.

If the firing button has been released the sear will rise & engage the bent of the locking Piece thus holding the B/B to the sear

Action of Magazine.

As the B/B moves forward taking with it the round held in the lips the next round in the mag is forced down on to the top of the B/B where it rests. This is done by the natural action of the Mag. spring. When the B/B has moved sufficiently to the rear to clear the round it is further forced into the lips of the mag

Action of Sear.

If the firing mechanism is released the sear spring will re-assert itself and raise the sear to project into the body of the gun. When the B/B travels to the rear the locking piece will override the sear depressing it compressing the sear spring. As soon as the locking piece is clear the sear will be returned by its spring ready to engage the L.P. Bent as the B/B rebounds off the buffer. When the L.P. engages the sear, the [indecipherable word] is driven forward, causing the sear slide to compress the sear buffer springs against the steel plate & [indecipherable word] buffer which absorb

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unlocking plates have travelled back thus half is allowing the unlocking cams of the unlocking plates to come into engagement with the unlocking cams of the locking piece lifting it out of engagement with the locking shoulder.

During this action the round has now cleared the end of the second reducer. The gasses coming in contact with the recoil reduces are deflects outwards & backward through the 45° outlet thus assisting the natural recoil of the gun. During the recoil movement the recoil spring has been compressed against the front mounting unit & the air piston moved backwards uncovering the inlet ports of the front mounting unit. During the natural return of the recoil spring a gassing effect is damped down by the compression of the air trapped in the air cylinder by the air piston, thus preventing damage to the front mounting unit & front mounting.

The residual gases which are left in the barrel (after the round has cleared recoil reduces) acting back through the empty case which in turn forces the B/B to the rear compressing the return spring. As the B/B moves to the rear a round being held by the extractor is expelled from the chamber & ejected through the ejector opening, when the B/B has travelled sufficiently

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[underlined] Cocking by air [/underlined]:- when cocking piston is forced to the rear by air pressure the piston lever engages the [indecipherable word] of the right hand locking plate forcing the B/B to the rear compressing the return spring. The air cocking piston is returned to the forward position having been extended during the cocking action

[underlined] [indecipherable word] movement [/underlined]

(Magazine) [indecipherable words] when the firing mechanism operated the sear is disengaged from [indecipherable words] the locking piece the B/B being forced forward by the return spring. Front face of the B/B engaging the base of the round held in the lips of magazine forcing it forward into the chamber, the rim of the cartridge being guided down the B/B face & engaging in the extractor. When the B/B comes to rest against the chamber the locking piece is forced down in to engagement with a locking shoulder by the locking cams of the B/B guides engaging the locking cams of the locking piece the unlocking plates are now free to move forward a further 1/2” making positive the locking of the B/B. The unlocking plates

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move forward under the influence of the return spring acting on firing pin & the unlocking plate spring acting on a thrust pin As the unlocking plates move forward the latter which is in engagement with both plates carries with it the firing pin & firing the cartridges. Thus the B/B is positively locked before the round is fired. Forward movement of the latter being assisted by the [indecipherable words] in the B/B.

[underlined] Backward Action [/underlined] 2840

When a round is fired the gases travelling down the barrel pass the gas vent where a portion of the gases are deflected through the vent, through the gas plug on to the head of the gas piston forcing it to the rear compressing the piston return spring. As the piston moves to the rear the gas piston [indecipherable word] engage the unlocking plate rods forcing them to the rear & these in turn force the unlocking plates to the rear as the unlocking plates are moved to the rear they carry with them the cotter & firing pin withdrawing the firing pin from the firing pin hole. The backward movement of the cotter is assisted by the cotter plate. During the movement the

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[underlined] ARMAMENT PUBLICATION [/underlined]

AP. 942 / Notes on [indecipherable word] armament experimental station with sites & tactics on [indecipherable word] gunnery

AP 1086 / Armament Stores & Explosives

AP 1180 / Supply dropping [indecipherable word]

1242 / Armament trainer manual Machining [indecipherable word] Small arms Etc (Vol. 1 & 2)

1243 / Bomb & sites

1244 / Training courses

1245 / Ranges & Armament buildings

1641 / (a) Vickers Recoil Guns
(b) Vickers Gas Operated
(c) Browning Gun
(d) Lewis Gun
(e) Firing Control Mechanism
(f) Hispano 20mm Cannon Belt filling position [indecipherable word]

1659 / (A) Frazer Nash Turret
(b) Bristol Turret
(c) Boulton Paul
(d) [indecipherable words] Turret
e Vickers Armstrong

1661. / Pyrotechnics

1749. / Cine Guns

1730 / A Bomb Sights
B Gun Sights

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[diagram of bullets]

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[back cover] [underlined] Powder [/underlined]

Collection

Citation

Colin McDermott, “Gunnery School Notes,” IBCC Digital Archive, accessed February 8, 2025, https://ibccdigitalarchive.lincoln.ac.uk/omeka/collections/document/27353.

Item Relations

This item has no relations.