Gun laying is the process of aiming an artillery piece, such as a gun,
howitzer or mortar, on land or at sea, against surface or air targets.
It may be laying for direct fire, where the gun is aimed similarly to
a rifle, or indirect fire, where firing data is calculated and applied
to the sights. The term includes automated aiming using, for example,
radar-derived target data and computer-controlled guns.
Gun laying means moving the axis of the bore of the barrel in two
planes, horizontal and vertical. A gun is "traversed" (rotated in a
horizontal plane) to align it with the target, and "elevated" (moved
in the vertical plane) to range it to the target.
2.2 Early mechanical gunnery aids
2.3 Modern era of gunlaying
2.3.1 Indirect artillery fire
2.3.2 Coastal & naval gun laying advances
Fire control systems
2.3.4 Anti-aircraft gun laying
3 See also
Manual traverse for an Eland armoured car.
Gun elevation is controlled
by the left traverse wheel, horizontal turret rotation by the right.
Gun laying is a set of actions to align the axis of a gun barrel so
that it points in the required direction. This alignment is in the
horizontal and vertical planes.
Gun laying may be for direct fire,
where the layer sees the target, or indirect fire, where the target
may not be visible from the gun.
Gun laying has sometimes been called
"training the gun".
Laying in the vertical plane (elevation angle) uses data derived from
trials or empirical experience. For any given gun and projectile
types, it reflects the distance to the target and the size of the
propellant charge. It also incorporates any differences in height
between gun and target. With indirect fire, it may allow for other
variables as well.
With direct fire, laying in the horizontal plane is merely the line of
sight to the target, although the layer may make allowance for the
wind, and with rifled guns the sights may compensate for projectile
"drift". With indirect fire the horizontal angle is relative to
something, typically the gun's aiming point, although with modern
electronic sights it may be a north-seeking gyro.
Depending on the gun mount, there is usually a choice of two
trajectories. The dividing angle between the trajectories is about 45
degrees, it varies slightly due to gun dependent factors. Below 45
degrees the trajectory is called "low angle" (or lower register),
above is "high angle" (or upper register). The differences are that
low angle fire has a shorter time of flight, a lower vertex and
flatter angle of descent.
All guns have carriages or mountings that support the barrel assembly
(called the ordnance in some countries). Early guns could only be
traversed by moving their entire carriage or mounting, and this lasted
with heavy artillery into World War II. Mountings could be fitted into
traversing turrets on ships, coast defences or tanks. From circa 1900
field artillery carriages provided traverse without moving the wheels
The carriage, or mounting, also enabled the barrel to be set at the
required elevation angle. With some gun mounts it is possible to
depress the gun, i.e., move it in the vertical plane to point it below
the horizon. Some guns require a near-horizontal elevation for
loading. An essential capability for any elevation mechanism is to
prevent the weight of the barrel forcing its heavier end downward.
This is greatly helped by having trunnions (around which the elevating
mass rotates vertically) at the centre of gravity, although a
counterbalance mechanism can be used. It also means the elevation gear
has to be strong enough to resist considerable downward pressure but
still be easy for the gun layer to use.
Until recoil systems were invented in the late 19th century and
integrated into the gun carriage or mount, guns moved substantially
backwards when they fired, and had to be moved forward before they
could be laid. However, mortars, where the recoil forces were
transferred directly into the ground (or water, if mounted on a ship),
did not always require such movement. With the adoption of recoil
systems for field artillery, it became normal to pivot the saddle on
the lower carriage, initially this "top traverse" was only a few
degrees but soon offered a full circle, particularly for anti-aircraft
guns. The introduction of recoil systems was an important milestone.
36-pounder long gun
36-pounder long gun at the ready.
The earliest guns were loaded from the muzzle. They were typically
little more than bare barrels moved in wagons and placed on the ground
for firing, then wooden frames and beds were introduced. Horizontal
alignment with the target was by eye, while vertical laying was done
by raising the muzzle with timber or digging a hole for the closed
Gun carriages were introduced in the 15th century. Two large-diameter
wheels, axle-tree and a trail became the standard pattern for field
use. The barrel was mounted in a wooden cradle with trunnions to mount
it on the carriage. As technology improved, the trunnions became part
of the barrel and the cradle was abandoned. Nevertheless, they were
relatively large and heavy.
Horizontal alignment was a matter of moving the trail. To achieve the
required elevation angle, various arrangements were used. At the
simplest, it was wedges or quoins between the breech and the trail,
but wooden quadrants, or simple scaffolds mounted on the trail, were
also used to support the breech and provided larger choice of
elevation angle. Screw elevation devices were also used as early as
the 16th century.
A naval cannon mounted on its gun carriage. The breech rope is
However, naval and some fortress carriages and mounting evolved
differently. Field mobility was not required, so large wheels and
trails were irrelevant. Headspace below decks was often low. This led
to compact carriages, mostly on four small wheels. Obviously, large
horizontal traverses were more difficult, but such things were
unnecessary when shooting broadside. However, in fortresses wider
traverse was required. One solution was platform and slide mountings.
Wide traverse was also useful on some shipmounted guns.
Laying required sights. At its simplest, this means nothing more than
aiming the guns in the right direction. However, various aids emerged.
Horizontal aiming involved sighting along the barrel, this was
enhanced by a notch made in the ring around the barrel at the breech
end and an 'acorn' on the ring around the muzzle. This was still used
in the 19th century in some instances.
The range with a flat trajectory was called 'point blank' range.
However, while point blank may have been enough for some purposes,
field artillery (whether mobile or static) and guns in fortresses
needed longer range. This required ways to measure elevation angles
and know the relationship between the elevation angle and the range.
Early mechanical gunnery aids
Various 16th-century artillery pieces, including culverin, falconet
The first recorded device to measure an elevation angle was Niccolò
Tartaglia's invention of a gunners' quadrant circa 1545. This device
had two arms at right angles connected by an arc marked with angular
graduations. One arm was placed in the muzzle, and a plumb bob
suspended against the arc showed the elevation angle. This led to many
calculations relating elevation angle to range.
The problem was that these calculations assumed what today is called
an "in vacuo" trajectory – they made no allowance for air resistance
against the projectile. What was needed were range and accuracy trials
to determine the actual relationship between range and elevation
angle. The practical approach was conducted by William Eldred,
Master Gunner at Dover Castle, in gunnery trials in 1613, 1617 and
1622. He used a wide variety of guns, including the culverin,
demiculverin, falconet and Saker. From the results of these trials, he
produced range tables for elevations up to 10 degrees for each type
with a standard propelling charge weight.
A problem affecting gun laying, was the tapered external barrel shape.
This affected elevation when the gun was aimed by sighting along the
top of the barrel. In the early 17th century, 'dispart sights'
compensated for this. This was a piece of metal placed on the muzzle
to make the line of sight parallel to the axis of the bore. Another
technique involved measuring the depth of the barrel through the
touchhole and at the muzzle, the difference being the wedge size
needed to compensate for the tapered barrel.
Ballistic pendulum, invented by
Benjamin Robins to calculate muzzle
The ballistic pendulum was invented in 1742 by English mathematician
Benjamin Robins, and published in his book New Principles of Gunnery,
which revolutionized the science of ballistics, as it provided the
first way to accurately measure the velocity of a bullet.
Robins used the ballistic pendulum to measure projectile velocity in
two ways. The first was to attach the gun to the pendulum, and measure
the recoil. Since the momentum of the gun is equal to the momentum of
the ejecta, and since the projectile was (in those experiments) the
large majority of the mass of the ejecta, the velocity of the bullet
could be approximated. The second, and more accurate method, was to
directly measure the bullet momentum by firing it into the pendulum.
Robins experimented with musket balls of around one ounce in mass (30
g), while other contemporaries used his methods with cannon shot of
one to three pounds (0.5 to 1.4 kg).
The first system to supplant ballistic pendulums with direct measures
of projectile speed was invented in 1808, during the Napoleonic Wars
and used a rapidly rotating shaft of known speed with two paper disks
on it; the bullet was fired through the disks, parallel to the shaft,
and the angular difference in the points of impact provided an elapsed
time over the distance between the disks. A direct electromechanical
clockwork measure appeared in 1840, with a spring-driven clock started
and stopped by electromagnets, whose current was interrupted by the
bullet passing through two meshes of fine wires, again providing the
time to traverse the given distance.
Tangent sights were introduced in the 19th century. These provided the
rear sight used with an 'acorn' or similar foresight at the muzzle.
The tangent sight was mounted in a bracket beside or behind the
breech, the eyepiece (a hole or notch) was atop a vertical bar that
moved up and down in the bracket. The bar was marked in yards or
degrees. This direct-fire sight was aimed at the target by moving the
trail horizontally and elevating or depressing the barrel. By the late
19th century the simple open tangent sights were being replaced by
optical telescopes on mounts with an elevation scale and screw aligned
to the axis of the bore.
Modern era of gunlaying
Canon de 75 modèle 1897
Canon de 75 modèle 1897 breech mechanism.
Rifled and breech loading artillery were introduced from the mid-19th
century, notably by William Armstrong, whose gun equipped Royal Navy
warships from the 1850s.
An important advance in the art of gun laying came with the
introduction of the first recoil mechanisms. The barrel recoil was
absorbed by hydraulic cylinders and then the barrel was returned to
its firing position by a spring that had stored some of the recoil
energy. This meant the gun did not have to be repositioned after
each time it was fired.
An early prototype incorporating this design feature was built in 1872
by Russian engineer, Vladimir Stepanovich Baranovsky. His 2.5-inch
rapid-firing gun was also equipped with a screw breech, a self-cocking
firing mechanism and it fired a fixed round (shell and cartridge case
together). The recoil mechanism was contained in the gun cradle.
Despite this effort, nothing followed from it, and it was only with
the introduction of the French 75 mm in 1897, that recoil systems
started to become normal. The gun's barrel slid back on rollers,
pushing a piston into an oil filled cylinder. This action absorbed the
recoil progressively as the internal air pressure rose and, at the end
of recoil, generated a strong but decreasing back pressure that
returned the gun forward to its original position. By this time
smokeless powder had replaced gunpowder as the standard propellant.
Naval range-finding instruments of 1936.
The first practical rangefinder was developed by Barr & Stroud a
pioneering Scottish optical engineering firm.
Archibald Barr and
William Stroud became associated from 1888. In 1891 they were
approached by the
Admiralty to submit a design for a short-base
rangefinder for trial, and in 1892 they were awarded with a contract
for six of their rangefinders. The device, operated by one person,
brought two images from a distance object into coincidence allowing
the distance to be calculated from their relative motions. 
Eyepiece image of a naval rangefinder, showing the displaced image
when not yet adjusted for range.
Now that the barrel remained aligned with the target after firing, the
more primitive tangent sight was replaced with the rocking-bar sight
for direct-fire sighting. These were installed on QF 4.7-inch
I–IV quick firing gun from 1887. The rocking-bar (or 'bar and drum')
sight had an elevation scale, could mount a telescope as well as the
open sight, and provided a small amount of horizontal deflection.
These provided 'independent line of sight' because they enabled data
to be set on the mount and the telescope (or open sight) aimed at the
target independent of the barrel elevation.
A related problem, particularly for large and longer range guns, was
that the wheels could be at different heights due to the slope of the
ground, which caused inaccuracy. Before the First World War, the
BL 60-pounder gun
BL 60-pounder gun was fitted with oscillating (reciprocating)
sights, using sighting telescopes, a sight clinometer and range scale
as well as a deflection drum for the telescope. These mounts could be
cross-leveled, which removed the need for the gun commander to
calculate a deflection correction for uneven wheels.
Cross-leveling introduced the third axis into laying.
Indirect artillery fire
Recoil mechanism on the
BL 60-pounder gun
BL 60-pounder gun Mk. I, 1916.
Modern indirect fire dates from the late 19th century. In 1882,
Russian Lt Col KG Guk, published Field
Artillery Fire from Covered
Positions that described a better method of indirect laying (instead
of aiming points in line with the target). In essence, this was the
geometry of using angles to aiming points that could be in any
direction relative to the target. The problem was the lack of an
azimuth instrument to enable it; clinometers for elevation already
The Germans solved this problem by inventing the Richtfläche, or
lining-plane, in about 1890. This was a gun-mounted rotatable open
sight, mounted in alignment with the bore, and able to measure large
angles from it. Similar designs, usually able to measure angles in a
full circle, were widely adopted over the following decade. By the
early 1900s the open sight was sometimes replaced by a telescope and
the term goniometer had replaced "lining-plane" in English.
The first incontrovertible, documented use of indirect fire in war
using Guk's methods, albeit without lining-plane sights was on 26
October 1899 by British gunners during the Second Boer War.
Although both sides demonstrated early on in the conflict that could
use the technique effectively, in many subsequent battles, British
commanders nonetheless ordered artillery to be "less timid" and to
move forward to address troops' concerns about their guns abandoning
them. The British used improvised gun arcs with howitzers; the
sighting arrangements used by the Boers with their German and French
guns is unclear.
A 1904 Russian lining plane sight.
Optical sights appeared in the first years of the 20th century, and
the German Goerz panoramic sight became the pattern for the rest of
the 20th century. They were graduated in degrees and 5 minute
intervals, decigrads or mils (4320, 4000 or 6000/6300/6400 to a
A feature of 20th-century laying was the use of one- or two-man
laying. The US was notable for using two-man laying, horizontal on one
side of the gun, elevation on the other. Most other nations mostly
used one-man laying. The laying drill, dealing with all three axes,
typically adopted this sequence: "roughly for line, roughly for
elevation, cross-level, accurately for line, accurately for
The other main difference in sighting arrangements was the use of an
elevation angle or alternatively the range. This issue became more
World War I
World War I when the effects of barrel wear in changing
muzzle velocity were fully recognised. This meant that different guns
needed a different elevation angle for the same range. This led many
armies to use an elevation angle calculated in a battery command post.
However, in the 1930s the British adopted calibrating sights in which
range was set on the sight, which automatically compensated for the
difference of muzzle velocity from standard.
An alternative to this was a 'gun rule' at each gun; in this case the
range was set on the rule and an elevation angle read and given to the
layer to set on the sight. The issue was finally resolved by the
introduction of digital computers in the battery command post that
calculated the correct elevation angle for the range and muzzle
velocity accurately and quickly.
Apart from calibrating sights, there was no significant difference in
field artillery laying arrangements for most of the 20th century.
However, in the 1990s new or modified guns started adopting digital
sights, following their successful use in the multi-launch rocket
system developed in the 1970s. In these the azimuth and elevation were
entered manually or automatically into a layers computer, then guided
the layer's use of horizontal and elevation controls until the barrel
was in the required horizontal and vertical alignment. This computed a
correction for the cross level of the gun and used feedback from
electro-mechanical devices, such as gyroscopes and electronic
clinometers, aligned to the axis of the bore. These devices were
subsequently replaced by ring laser gyros.
Coastal & naval gun laying advances
The Range Finder Building, built into the cliff face at St. David's
Battery, Bermuda, captured data that was used in the plotting room to
produce gun-laying data.
Most coastal artillery was in fixed defences, "fortresses" in some
form. Their targets moved in two dimensions, and the gun had to be
aimed at the target's future position. Some guns were relatively small
calibre and dealt with relatively close targets, others were much
larger for long-range targets.
Coast artillery employed direct fire, and until the late 19th century
laying had changed little, apart from gaining telescopic sights, over
Nineteenth-century improvements in gun design and ammunition greatly
extended their effective range. In 1879, Major HS Watkins of the Royal
Artillery invented the depression range finder, the
position-range finder and associated fire control.
His description explains its essence:
"The position-finder traces the course of the ship, and when the guns
are ready to lay, predicts the position the ship will occupy half a
minute or more in advance. The dials on the gun floor automatically
indicate the range and training to hit the predicted position. When
the guns are laid an electric tube (i.e., primer) is inserted and the
signal goes up to the observing station that all is ready for firing.
The non-commissioned officer in charge of the position-finder watches
for the appearance of the ship in the field of view of his telescope,
and when she arrives at the cross wires presses a button, and the guns
It took almost 20 years to get it to full effectiveness, but its
general principle became the norm for heavy artillery fire control and
laying. Shorter-range guns retained conventional direct-fire laying
with telescopes for much longer. In the 20th century, coast artillery,
like field and the larger anti-aircraft guns, included corrections for
non-standard conditions such as wind and temperature in their
Fire control systems
Main article: Fire-control system
Accurate fire control systems were introduced in the early 20th
century. Pictured, a cut-away view of a destroyer. The below decks
analog computer is shown in the centre of the drawing and is labelled
"Gunnery Calculating Position".
Naval artillery on board capital ships soon adopted gunlaying
arrangements broadly similar to Major Watkins' coast artillery
pattern. The introduction of breech-loading guns, then recoil systems
and smokeless powder, completed the change in warship armament from
hull-mounted to turreted guns.
However, ships had a complication compared to land based guns: they
were firing from a moving platform. This meant that their laying
calculations had to predict the future position of both ship and
target. Increasingly sophisticated mechanical calculators were
employed for proper gun laying, typically with various spotters and
distance measures being sent to a central plotting station deep within
the ship. There the fire direction teams fed in the location, speed
and direction of the ship and its target, as well as various
adjustments for Coriolis effect, weather effects on the air, and other
The resulting directions, known as a firing solution, would then be
fed back out to the turrets for laying. If the rounds missed, an
observer could work out how far they missed by and in which direction,
and this information could be fed back into the computer along with
any changes in the rest of the information and another shot attempted.
Rudimentary naval fire control systems were first developed around the
time of World War I.
Arthur Pollen and Frederic Charles Dreyer
independently developed the first such systems. Pollen began working
on the problem after noting the poor accuracy of naval artillery at a
gunnery practice near
Malta in 1900. Lord Kelvin, widely regarded
as Britain's leading scientist first proposed using an analogue
computer to solve the equations which arise from the relative motion
of the ships engaged in the battle and the time delay in the flight of
the shell to calculate the required trajectory and therefore the
direction and elevation of the guns.
Pollen aimed to produce a combined mechanical computer and automatic
plot of ranges and rates for use in centralised fire control. To
obtain accurate data of the target's position and relative motion,
Pollen developed a plotting unit (or plotter) to capture this data. He
added a gyroscope to allow for the yaw of the firing ship. Again this
required substantial development of the, at the time, primitive
gyroscope to provide continuous reliable correction. Trials were
carried out in 1905 and 1906, which although completely unsuccessful
showed promise. He was encouraged in his efforts by the rapidly rising
figure of Admiral Jackie Fisher, Admiral
Arthur Knyvet Wilson
Arthur Knyvet Wilson and the
Director of Naval Ordnance and Torpedoes (DNO), John Jellicoe. Pollen
continued his work, with tests carried out on Royal Navy warships
Admiralty Fire Control Table in the transmitting station of HMS
Meanwhile, a group led by Dreyer designed a similar system. Although
both systems were ordered for new and existing ships of the Royal
Navy, the Dreyer system eventually found most favour with the Navy in
its definitive Mark IV* form. The addition of director control
facilitated a full, practicable fire control system for World War I
ships, and most RN capital ships were so fitted by mid 1916. The
director was high up over the ship where operators had a superior view
over any gunlayer in the turrets. It was also able to co-ordinate the
fire of the turrets so that their combined fire worked together. This
improved aiming and larger optical rangefinders improved the estimate
of the enemy's position at the time of firing. The system was
eventually replaced by the improved "
Admiralty Fire Control Table" for
ships built after 1927.
By the 1950s gun turrets were increasingly unmanned, with gun laying
controlled remotely from the ship's control centre using inputs from
radar and other sources.
Telescopic sights for tanks were adopted before World War II, and
these sights usually had a means of aiming off for target movement and
graticules marked for different ranges.
Tank sights were of two
general types. Either the sight was in fixed alignment with the axis
of the bore with ranges marked in the sight, and the gunner laid the
range mark on the target. Or during laying the gunner physically set
the range to offset the axis of the bore from the axis of the sight by
the correct amount and laid using the centre mark in the sight.
Some sights had a means of estimating the range, for example using a
stadiametric method. Other tanks used an optical coincident
range-finder or after World War II, a ranging machine gun. From the
1970s these were replaced by laser range finders. However, tank guns
could not be fired accurately while moving until gun stabilisation was
introduced. This appeared at the end of World War II. Some were
hydraulic, while others used electrical servos. During the 1970s tanks
started being fitted with digital computers.
Anti-aircraft gun laying
A French anti-aircraft motor battery (motorized AAA battery) that
brought down a
Zeppelin near Paris. From the journal Horseless Age,
The need to engage balloons and airships, from both the ground and
ships, was recognised at the beginning of the 20th century. Aircraft
were soon added to the list and the others fell from significance.
Anti-aircraft was direct fire, the layer aiming at the aircraft.
However, the target is moving in three dimensions and this makes it a
difficult target. The basic issue is that either the layer aims at the
target and some mechanism aligns the gun at the future (time of
flight) position of the target or the layer aims at the future
position of the aircraft. In either case the problem is determining
the target's height, speed and direction and being able to 'aim-off'
(sometimes called deflection laying) for the anti-aircraft projectile
time of flight.
German air attacks on the
British Isles began at the beginning of the
First World War. Anti aircraft gunnery was a difficult business. The
problem was of successfully aiming a shell to burst close to its
target's future position, with various factors affecting the shells'
predicted trajectory. This was called deflection gun-laying, 'off-set'
angles for range and elevation were set on the gunsight and updated as
their target moved. In this method when the sights were on the target,
the barrel was pointed at the target's future position. Range and
height of the target determined fuze length. The difficulties
increased as aircraft performance improved.
The British dealt with range measurement first, when it was realised
that range was the key to producing a better fuse setting. This led to
the Height/Range Finder (HRF), the first model being the Barr &
Stroud UB2, a 2-metre optical coincident rangefinder mounted on a
tripod. It measured the distance to the target and the elevation
angle, which together gave the height of the aircraft. These were
complex instruments and various other methods were also used. The HRF
was soon joined by the Height/Fuze Indicator (HFI), this was marked
with elevation angles and height lines overlaid with fuze length
curves, using the height reported by the HRF operator, the necessary
fuse length could be read off.
A Canadian anti-aircraft unit of 1918, running to stations.
However, the problem of deflection settings—'aim-off'—required
knowing the rate of change in the target's position. Both France and
UK introduced tachymetric devices to track targets and produce
vertical and horizontal deflection angles. The French Brocq system was
electrical, the operator entered the target range and had displays at
guns; it was used with their 75 mm. The British Wilson-Dalby gun
director used a pair of trackers and mechanical tachymetry; the
operator entered the fuse length, and deflection angles were read from
In 1925 the British adopted a new instrument developed by Vickers. It
was a mechanical analogue computer Predictor AA No 1. Given the target
height its operators tracked the target and the predictor produced
bearing, quadrant elevation and fuze setting. These were passed
electrically to the guns where they were displayed on repeater dials
to the layers who 'matched pointers' (target data and the gun's actual
data) to lay the guns. This system of repeater electrical dials built
on the arrangements introduced by British coast artillery in the
1880s, and coast artillery was the background of many AA officers.
Similar systems were adopted in other countries and for example the
later Sperry device, designated M3A3 in the US was also used by
Britain as the Predictor AA No 2. Height finders were also increasing
in size, in Britain, the
World War I
World War I Barr & Stroud UB 2 (7 feet
optical base) was replaced by the UB 7 (9 feet optical base) and the
UB 10 (18 feet optical base, only used on static AA sites). Goertz in
Germany and Levallois in France produced 5 metre instruments.
World War II
World War II the situation was largely as follows: for targets up
to a few thousand yards away, a smaller-calibre automatic gun was
used, with simple sights that enabled a layer to judge the lead based
on estimates of target range and speed; for longer-range targets,
manually controlled predictors were used to track the target, taking
inputs from optical or radar rangefinders, and calculating firing data
for the guns, including allowance for wind and temperature.
World War II
World War II predictors changed from being electro-mechanical
analogue computers to digital computers, but by this time heavy
anti-aircraft guns had been replaced by missiles, but electronics
enabled smaller guns to adopt fully automated laying.
Gun data computer
Enfilade and defilade
Gun laying radars
^ Hogg pp. 97 – 98
^ Hogg pp. 98 – 99
^ Hogg illus. 6, 8, 9 and 11
^ a b Hogg pp. 239 – 240
^ Hogg pp. 238 – 239
^ Hogg pp. 75, 273
^ a b "Chronograph". Encyclopædia Britannica, 11th Ed (1911).
Archived from the original on 2011-07-26.
^ a b Edward John Routh (1905). The Elementary Part of A Treatise on
the Dynamics of a System of Rigid Bodies. Macmillan.
^ Hogg pp. 240 – 241
^ Bellamy pg 13
^ Bellamy pg. 23
^ Archives of Barr and Stroud Archived 2008-03-30 at the Wayback
^ Robert Bud, Deborah Jean Warner (1998). Instruments of Science: An
Historical Encyclopedia. Taylor & Francis. p. 182.
^ Headlam Vol 2 pg. 96 - 97
^ a b Frank W. Sweet (2000). The Evolution of Indirect Fire.
Backintyme. pp. 28–33. ISBN 0-939479-20-6.
^ The History of the Royal
Artillery from the Indian Mutiny to the
Great War, Vol II, 1899–1914, Major General Sir John Headlam, 1934
^ Headlam Vol 1 pg 302
^ For a description of one, see US Naval Fire Control, 1918.
^ Pollen 'Gunnery' p. 23
^ Pollen 'Gunnery' p. 36
^ a b c Routledge (1994). History of the Royal regiment of
Artillery – Anti-Aircraft
Artillery 1914–55. London:
Brassey's. pp. 14–50. ISBN 1-85753-099-3.
Bellamy, Chris. 1986. Red God of War – Soviet artillery and rocket
forces London: Brassey's, ISBN 0-08-031200-4
Callwell, Major General Sir Charles and Headlam, Major General Sir
John. 1931. The History of the Royal
Artillery – From the Indian
Mutiny to the Great War - Volume 1 (1860–1899). Woolwich: Royal
Headlam, Major General Sir John. 1934. The History of the Royal
Artillery – From the Indian Mutiny to the Great War - Volume 2
(1899–1914). Woolwich: Royal
Hogg, Brigadier OFG. 1970. Artillery: Its origin, heyday and decline.
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The Official History of the Ministry of Munitions, Vol X The Supply of
Munitions, Part VI Anti-Aircraft Su