75-MM GUN M1897, U.S. ARMY

U.S. Army Field Manuel March 31, 1941

A maximum rate of fire of 25 to 18 rounds per minute may be attained, but the advisable rate is 6 rounds.

M1897 and M1897M1A2 75-mm Gun
Weight of gun – 2,657 pounds
Length of recoil – 44.9 inches
Maximum elevation – 19 degrees

DESCRIPTION OF 75-MM GUN
The gun is of French design. A number of these weapons were purchased by the United States. Similar guns were manufactured in the United States. The parts of the American and French manufactured guns are identical and therefore interchangeable.

The gun is the built-up type. Name and model are stamped on the left side of the breech hoop. Name of manufacturer, year of manufacture, serial number and weight, including breech mechanism, are stamped on the muzzle. Data on guns bought from France will be found on top of breech end.

M1897A4 and M1897A2 – The M1897A4 gun is a modification of the 75-mm gun, M1897 (French). The modification consists of the removal of rollers and sweeper plates with felt pads, and elimination of a portion of the jacket of the gun which is replaced by steel rails and bronze strips attached to supports on the gun.

M1897A2 gun is standard for new manufacture and is similar in design to the 75-mm gun, M1897A4

Operation of beech and firing mechanism- to open the breech unlatch breechblock latch by pressing on operating handle plunger with the thumb. Grasp operating handle with both hands toward the forward position. This will protect the little finger of the left hand from danger of injury by crushing between the pawl and rear sight. Pull upward and pust over to left until breechblock arm stops against breechblock stop.

To close breech grasp operating handle as in opening the breech, and pull to the right and down until breechblock arm strikes projection stop on lower right on breech face. At the end of this movement the inner end of the breechblock latch springs into the grooves in the latch catch in the breech face of the gun, latching the breech mechanism in closed position.

Firing mechanism – to fire the piece, pull lanyard sharply down and to the right and release lanyard. This allows the hammer to be thrown forward against the firing pin by means of the firing rack spring with sufficient force to explode the primer.

Safety piece is provided to prevent accidental firing. The safety piece screws into the threaded recess in the breechblock arm, and maybe located at two different points. These two points are marked “Safe and Fire” on the outer surface of the breechblock arm. On guns of French manufacture, these two points are marked “ Tir and Route”

Description of carriages – M1897, M1897A2, M1897M1, M1897M1A2 and M1897M1A4 – these gun carriages are of the hydropneumatic, constant recoil type in which the gun when fired recoils a sufficient length to permit the carriage to remain stationary.

The 75-mm gun carriage M1897 (French) was designed and manufactured in France. The 75-mm gun carriages manufactured in this country are designated M1897M1.

When the M1897 or M1897M1 carriages are equipped with handspike, model designation of the M1897 carriage is changed to M1897M1A2 and of the M1897M1 carriage is changed to M1897M1A2. When the M1897, M1897A2, M1897M1, and M1897M1A2 carriages are equipped with high-speed adapters, the model designation is changed to M1897M1A4

Recoil mechanism – the recoil mechanism controls the force created by firing and checks movement of recoiling mass in a gradual manner so as not to cause displacement of the carriage. The recuperator system of the mechanism returns the recoiling mass into battery in order that the gun maybe fired again.

All recoil mechanisms, except the M1897, have been equipped with a respirator, which acts in conjunction with the recuperator in regulating counter recoil at different temperatures. The respirator head has four indentations in which the respirator cap spring seats when the valve is rotated. These indentations are numbered 0, 1, 2 and 3, indicating the number of holes which maybe opened to allow escape of air from the recoil cylinder during counter recoil.

Elevating mechanism – Located between rocker and cradle. Its function is to elevate or depress the gun with reference to the rocker. Thus the gun can be laid to the desired angle of elevation for range without disturbing the laying for angle of site or the line of sight.

Range rack and range scale mounting – Range rack, range scale, and range rack guide, front, have engraved scales which correspond to the various ranges. The scales are for setting the gun in elevation or depression. Spacing of the graduations is such that when the gun is elevated or depressed, the graduation opposite the index indicates the actual range. The range rack and the range scale are graduated for range in meters. The range rack registers for every 100 meters, and the range scale for every 50 meters. The range rack guide, front, is graduated for every 2 mils. Thus to set the gun for a given range, elevate or depress gun until corresponding graduation of the scale is opposite the index. If the range is given in meters the scale on the rack is used. If it is given in mils the scale on the range rack guide, front, is used.

Range scale is located above elevating crank on right of carriage.

The range scale indicates any movement between rocker and cradle.

Index marks on front and rear guides register the range and elevation on the range rack scale and range rack.

Angle of site mechanism – The angle of site mechanism is located between trail and rocker, and provides means for elevating or depressing the rocker with reference to the trail. By means of this mechanism the rocker can be laid to the desired angle of site without disturbing the angle of elevation.

The angle of site hand wheel is perforated with twelve holes, which can be engaged with its anglesite hand wheel latch thus locking the angle of site mechanism. The outer face of the angle of site hand wheel is divided into 16 equal spaces, which are stamped and numbered. One complete turn elevates or depresses the rocker 16 mils.

The angle of site pointer is a reference for reading graduations on the outer face of the angle of site hand wheel.

Traversing mechanism – the carriage can be trained on a target by shifting the trail. A means is provided, however, for closer training through the traversing mechanism. In traversing the carriage the front of the trail slides laterally on its bearings on the axle, describing an arc about the spade. Thus during traverse one wheel advances slightly ahead of the other.

Shield – The shield is for protection of the gun crew. The three types of shields are a four-piece shield of American manufacture, a four-piece shield of French manufacture, and a seven-piece shield. The American four-piece shield is interchangeable with the French four-piece shield, and either maybe used to replace the seven-piece shield. However, the seven-piece shield cannot be substituted on a carriage fitted for either type of four-piece shield.

Wheels – There are two types of 14-spoke wheels, one steel-tired and the other rubber-tired. They are interchangeable on M1897 and M1897M1A2 carriages.

AMMUNITONS
Ammunition for the 75-mm guns, M1897, M1897A2 and M1897A4, is issued in the form of “fixed” rounds, either unfuzed or as fuzed complete rounds. A complete round includes all of the ammunition components used in a cannon to fire one round.

Fixed ammunition – In fixed ammunition the cartridge case, which contains the propelling charge and primer, is crimped rigidly to the projectile. Until recently, designs of fixed rounds provided for issue of the round unfuzed, the fuze to be assembled just prior to firing. In current design the round is issued as a fixed complete round, the fuze being assembled to the round “as issued.”

Classification – Dependent upon the kind of filler, projectiles maybe classified according to type as explosive, chemical, or inert. Explosive projectiles comprise high explosive and practice, and shrapnel. High explosive projectiles contain a high explosive bursting charge, whereas shrapnel and practice projectiles contain a relatively small quantity of low explosive filler. The modern shrapnel is a projectile designed to carry a large number of spherical shot to a distance from the gun and there discharge them over an extended area. The low explosive filler for practice projectiles is intended solely as a spotting charge and for some purposes maybe omitted. Chemical projectiles comprise those containing a chemical filler, that is, a chemical agent which produces either a toxic or an irritating physiological effect, a screening smoke, an incendiary action, or a combination of these. Inert projectiles contain no explosives.

LIMBER AND CAISSONS
The Limber is a two-wheeled vehicle to which the trail of the carriage is fastened to form a four-wheeled complete carriage for the gun when traveling. The caisson is built primarily to carry ammunition. Fixtures are provided on the outside for holding such miscellaneous equipment as picks, shovels, and similar tools. A name plate, giving name, number, and model of the vehicle, name of manufacturer, year of completion, and initials of the inspector, is attached to each vehicle. All reports and correspondence concerning a particular vehicle must always refer to it by name, model, and serial number given on the nameplate. Location of nameplates on the various vehicles will be found in the description of the particular vehicles.

Description and use of limber and caisson limber – The 75-mm gun carriage limber, M1918, and the 75-mm gun caisson limber, M1918, are substantially the same, except for the ammunition chest. The limber chest carries 18 rounds of ammunition and 3 oil cans, whereas the caisson limber chest is larger, carrying 36 rounds of ammunition and 3 oil cans. The top of the chest forms a seat for the cannoneers. The hand wheel, M1917, attached to the caisson, is a hand-operated reel for transportation and handling of telephone wire. The reel is so mounted on top of the caisson chest that it can be removed readily and replaced by another spool. A removable crank is mounted on left end of the shaft. When removed it is held by a clip riveted to end of frame. A hinged crank, mounted on end of driving gear, is so designed that it may be folded compactly against the frame. When folded back, the crank is disengaged from the driving gear for controlling the speed of the spool. The spool maybe operated from either side. In laying out wire, the left crank is removed and placed in the clips of the left end of the frame, the pin is removed from the end of driving gear, and right crank is folded back and placed on crank rest, the drum then being free to revolve. Speed of the drum in paying out the wire is controlled by the action of the brake. In recovering wire place right and left cranks in position. Revolving left crank operates the driving gear, the right crank being connected directly to the shaft on which the spool is mounted. The reel is also fitted with a brake for controlling speed of rotation when allowing wire to run out. The brake lever is operated by a thong attached to lower end of the lever. A thong or cord long enough to reach to the seat of the limber, if desired, maybe reeved through lower end of brake lever to operate the brake mechanism. By pulling the thong the upper end of the lever is made to drag on inside of rim of left spool flange. A brake release spring attached to upper end of lever, and a lug on the left shaft bearing keeps brake open when not in use.

Common parts – Wheels, dust guards, singletrees, doubletrees, drawbars, poles, neck yokes, etc, are interchangeable when used with the proper vehicle.

Lunette- The ring in the trail of a gun carriage or rails of a caisson by which it is attached to the limber is called the lunette. The hook of the limber with which the lunette engages is called the pintle. The pintle is free to rotate. The lunette used for horse drawn batteries has a small eye. For motorized batteries trucks replace the limbers and a different type of lunette is used. This lunette has a larger eye and no provision is made for an automatic pole support. Therefore care should be taken that the proper type is used.

Padlocks – Limber and caisson ammunition chests are furnished with a padlock marked “Ammunition” which is supplied with one key only. All ammunition keys are interchangeable. The padlocks furnished for each separate vehicle other than those having ammunition chest are alike and are supplied with two keys each. Each padlock and the keys belonging to it are stamped with a serial number.

76th Field Artillery Battery “D” passing in review Presidio of Monterey 1920’s. DLIFLC & POM Archives

The above picture shows a limber (men sitting with arms crossed) connected and towing a 75-mm gun. The limber is designed to support the artillery piece for towing and is connected by means of a lunette and pinhook. The caisson is designed to carry ammuntion. The limber would usally be connected to a caisson or a artillery piece. The limber would tow a artillery piece or a caisson.

FIRE CONTROL INSTRUMENT U.S. ARMY FIELD ARTILLERY 1918-1940s

ORDNANCE EQUIPMENT
Reels, battery, M 1917 (4-horse, each reel carrying approximately 1.7 miles of field wire, W-40).
Range finder – The battery had one.
Aiming circles - The battery had two.
Battery commander’s telescope - The battery had one.
Field glasses, type EE - The battery had five.

QUARTERMASTER EQUIPMENT
Wagon, mountain - The battery had one. Used to carry field equipment including fire-control instruments.

SIGNAL EQUIPMENT
Flag kits (semaphore) - The battery had four.
Reels, type RI-9 (breast reels each carrying 200 yards of outpost wire, W-44).
Signal lamps, complete - The battery had three.
Switchboards, 4-drop, BD-9 - The battery had two.
Telephone, type EE-5 - The battery had seven.
Telephone, type EE-70 (headsets only) - The battery had four.
Wire reserve (not on reels) W-40 – 1.6 miles, W-44 – 960 yards.

ENGINEER EQUIPMENT
Alidade, brass, etc. - The battery had one.
Declinator - The battery had one.
Plane table, etc. - The battery had one.
Plotting scale - The battery had one.
Sketching outfit, complete - The battery had one.
Protractor - The battery had one.
Tape (measuring) 100 ft. (and pins) - The battery had one.
Steel straightedge - The battery had one.
Tent pegs - The battery had ten.

FIRE CONTROL INSTRUMENT U.S. FIELD ARTILLERY
Plane Table – use to create maps, plotting and firing charts, useful for locating points and measuring data. The plane table made creating the above more convenient in field conditions. Its disadvantages are that it is conspicuous, bulky to carry, and the work can not be exposed to wet weather.

Aiming Circle – is an instrument for use in measuring angles in azimuth and site, and for general survey work.

Battery Commander’s Telescope M-1915 – is a binocular observing instrument for use in measuring angles in azimuth and site. Range Finder M-1916 - is an instrument for use in measuring distances, angles in azimuth and site.

Prismatic Compass M-1918 – is for use in measuring azimuth angles in reference to magnetic north (magnetic bearings). It is also equipped with a clinometer, by means of which vertical angles in mils (angles of site) may be measured.

BATTERY COMMANDER’S TELESCOPE M1915A1

Description – The instrument complete includes a binocular telescope, mount, tripod, and as accessories the necessary carrying case, storage chest, and cleaning brushes. Modified instruments to be designated M1915A1,will be equipped for reticle illumination and will be designed to receive the instrument light, M1 Illumination of such instruments maybe supplied by flashlight until such time as the instrument light becomes available.

Telescopes are arranged so that they maybe positioned vertically or swung down horizontally.

Operation – To set-up the instrument, remove tripod and mount from the tripod carrying case, clamp tripod legs at desired length, embed them firmly in the ground, and tighten leg clamping levers. Remove telescope from its carrying case and place it on the vertical spindle extending from the mount, depressing locking plunger and turning telescope until mating surfaces of telescope and mount engage properly, then release plunger. Level the mount using the circular level and ball-and-socket joint at bottom of mount, and clamp with the lever bubble is centered.

To prepare the telescope, remove caps from eyepieces and objectives. If required, place sunshades over objectives and amber filters over eye lenses. Sunshades and filters are carried in compartments of the telescope case. Release telescope-clamping knob and turn telescopes to vertical or horizontal position as required, at the same time setting proper interpupillary distances in millimeters on associated scale, and clamp in place. If the interpupillary distance for observer is not known it maybe found by observing the sky and moving eyepieces apart or together until field of view changes from two overlapping circles to one sharply defined circle. Focus each eyepiece independently, looking through telescope with both eyes open at an object several hundred yards away, covering the front of one telescope and turning diopter scale until object appears sharply defined, then repeating for other eye. A diopter scale is provided for each eye and if observer remembers the values for his own eyes, settings maybe made directly on the scales. Turn reticle rotating ring until reticle appears erect.

To orient the instrument, select a datum point of known azimuth and set this value on azimuth scale (100-mil steps) and micrometer (1-mil steps). The throw-out lever maybe used to disengage the worm drive for making large changes in azimuth rapidly. Turn telescope by means of orienting knob until datum point appears at the center of reticle of right hand telescope. The orienting clamping knob maybe temporarily released for making large angular changes rapidly. Thereafter use only the azimuth knob or the large changes the azimuth throw-lever, and correct azimuth of point observed will be indicated. For azimuth in the 3,200-6,400 mil region additional numbers (0-3,200 mils) are provided corresponding to azimuth scales on panoramic telescopes and other instruments.

To read angle of site, swing angle of site mechanism into a substantially vertical plane. Direct telescope on the object and rotate elevating knob until object appears at center of reticle. By means of angle of site knob, center bubble of angle of site level in its vial. The angle of site is then read on angle of site scale (100-mil steps) and micrometer (1-mil steps). An indication of 300 mils corresponds to a horizontal line of sight.

The horizontal axis of the reticle is graduated at 5-mil intervals for 30 mils on each side of center. The two short lines above horizontal line are spaced 3 mils apart.

To prepare the instrument for traveling, remove sunshades and filters, if used, and place them in the pockets of telescope carrying case. Cover objectives and eyepieces. With telescope shanks in a vertical position, press locking plunger and lift telescope from mount. Loosen telescope clamping knob and swing elevating mechanism against right and left hand telescope. Instrument will then fit snugly into the blocking of the case. Do not remove mount from tripod. Tripod leg clamping levers should not protrude.

M-1916 RANGE FINDER, 1-M BASE

Finder, range, 1-m base, M1916 – This instrument is used primarily for measuring distance by triangulation. Indications of azimuth and angle of site are also provided.

Description – This instrument includes an internal 1-meter base line, a 15-power optical system with two objectives and a common eyepiece of the coincidence type, and a scale on which the distance in indicated. It is furnished complete with mount and tripod. Necessary carrying cases and adjusting equipment are provided as accessories. The mount positions the line of sight of the range finder in elevation and azimuth and provides a hinge joint for placing the base line axis of the instrument in either a vertical or horizontal position. Angle of site and azimuth scales and micrometers are provide on the mount.

Operation – To set up the instrument, securely clamp tripod legs at desired length, embed them firmly in the ground, and tighten leg clamping levers. It is necessary that azimuth scale is in a substantially horizontal plane. Place range finder on mount and latch it into position. Position longitudinal axis horizontally and clamp with hinge clamping handle.

To prepare optical system for use rotate end box sleeves, uncovering both windows. Set ray filter lever to proper position. No filter at all maybe used, or the amber filter (for exceptionally bright daylight or reflection of sun over water), or the smoke filter (for observation near the sun or into direct rays of a search-light) maybe employed. Focus eyepiece by rotating diopter scale to produce a clear image. It the operator know the value for his own eye, the setting maybe made directly on the scale.

To orient the instrument, select a datum point of known azimuth. Set this value on azimuth scale and micrometer. Loosen tripod head clamping lever and swing instrument until datum point appears near vertical centerline of field of view, indicated by a short line in lower field of view. Clamp lever and refine setting with azimuth adjusting (orienting) knob so that point appears exactly on vertical centerline.

To measure the range of the object, select a clearly defined part perpendicular, if possible, to the halving line. Move the instrument in azimuth and elevation as required to bring the part at center of field of view when in coincidence. On moving targets it is advisable to start with the target at edge of field of view so that it maybe brought into coincidence as it crosses the field. An open sight is provided for picking up the target. For large angular displacements in azimuth, depress throw-lever and turn instrument as required. When first observed images will ordinarily not be in coincidence. Turn range knob until images of points selected appear in coincidence. Read range in yards on range drum opposite sliding range pointer.

To measure range of horizontal objects such as roads, trenches, crests of ridges, etc., which have prominent vertical parts, turn instrument with longitudinal axis vertical, temporarily loosening hinge-clamping handle for the purpose. Images when first observed will ordinarily not be in coincidence. Turn the range knob until the image of horizontal line appears to continue across the halving line. Temporarily lower the support-clamping lever for any necessary motion in elevation (within limits of plus or minus 10 degrees)

To read angle of site, center level bubble using angle of site knob. The angle of site indication may then be on associated scale (100-mil steps) and micrometer (1-mil steps). An indication of 300 mils corresponds to a horizontal line of sight. Angle of site can be read only when using the instrument with longitudinal axis horizontal.

To read azimuth, the azimuth scale (100-mile scale) and micrometer (1-mil steps) furnish the necessary indications. It is essential that the plane of the azimuth scale be substantially level and that the object be at the center of field of view for the correct angular indications. Azimuth maybe measured with longitudinal axis either vertical or horizontal, but the instrument must be oriented separately for each position. Azimuths from 3,200 to 6,400 mils have an additional auxiliary scale reading from 0 to 3,200 mils for use with panoramic telescopes similarly graduated. To prepare instrument for traveling, cover the eyepiece, close the end box sleeves and the cover over the range drum. Remove range finder from mount and place in its case. Place mount and tripod in their case, with elevating knob toward inside of case. Do not remove mount for tripod. Remove sight from adjusting lath. Place lath in internal pocket of tripod carrying case and sight in lid pocket. The latter pocket also contains the correction wedge key and camel’s hair brush.

AIMING CIRCLE M-1918 (FRENCH) AND M-1 (NEW AMERICAN)

76th Field Artillery regiment pictured with M1915A1 Commander’s Telescopes and M1918 Aiming Circles (French) at Camp Ord (Gigling) Reservation, Monterey, California, c1933. DLIFLC & POM Archives

M-1918 (French) Aiming Circle.

The Aiming Circle M-1918 (French) and the M-1 (New American) has only slight differences in construction and in operation. The reticle in the telescope part of an aiming circle contains a vertical mil-and-stadia scale. They both use the same tripod. The M1918 French model and M1916 were used by the U.S. artillery until the M-1 (U.S., New American) was introduced in the late 1930’s. The M-1918 was used during WW1 by the U.S. Army artillery using the French 75mm guns. The “plateau scale” (“k” in figure 52) was used in conjunction with the sight graduations on the gun carriage of the model of 1897 M1, 75mm gun and consisted of a quadrant subdivided into 200-mil spaces, each halved – one half plain and the other crosshatched. The aiming circle is an instrument used for measuring angles azimuth and site, and for simple survey work. The aiming circle consists of the aiming circle proper, the tripod, instrument light and the carrying case.

M-1 (New American) Aiming Circle. My display of the M-1 at Fort Ord Warhorse Day 2013. The M-1918 (French) and M-1 are almost identical and they use the same tripod.

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