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HEAVY FIELD AND SIEGE] action in the open when necessary. At short ranges, with full charge, they make very powerful guns.

Construction of the Carriage.—The gun-recoil system is used as in a gun equipment. There is however one important difference. If the recoil allowed be sufficient to keep the carriage steady at low elevations, then when fired at an elevation of 45° the breech will strike the ground. This may be to some extent avoided by placing the trunnions of the cradle which supports the howitzer at the extreme rear end, so that when elevated the breech of the howitzer is not brought any nearer the ground (Krupp). One objection to this is that the forward preponderance of the howitzer has to be balanced by a spring to enable it to be elevated.

A second method is known as controlled recoil. The buffer-liquid, on recoil, has to pass through holes in the piston. The access of the buffer-liquid to these holes is controlled by a disk valve rotated by rifled grooves in the cylinder. By connecting the piston-rod to the carriage so as to rotate the piston when the gun is elevated, the area of the holes exposed by the disk valve can be decreased at high elevations so as to shorten the recoil. This is known as the Vavasseur-Ehrhardt control valve. Messrs Cockerill use a channel through which the liquid is forced on recoil, which is partly closed by a stopcock connected to the left trunnion when the howitzer is elevated. The running-up springs require to be strong in order to lift the weight of the howitzer at 45° elevation. In most equipments twin columns of springs are used. EB1911 - Ordnance Fig 66.png . 66.—Wagon Body, Rumanian (Krupp) Quick-firing Field Gun.

The Ehrhardt Q.F. Field Howitzer, fig. 67 (Plate IV.), may be taken as a type of the light field howitzer with controlled recoil, as opposed to the Krupp pattern with rear trunnions and constant long recoil. The howitzer is represented immediately after firing, before it has run up. The recoil is automatically shortened so that when fired at this high elevation the buffer, which is seen under the breech, does not strike the ground. The sights are on the bar which passes through the shield. The calibre is 4·7 in.; the howitzer fires a 46 ℔ shell with M.V. 985 f.s., and weighs 25 cwt. in action with shield.

The Q.F. Mountain Gun.—A mountain gun has the same tactical duties to fulfil as a field gun. It is merely a field gun sufficiently mobile for mountain transport. Its weight and dimensions are restricted by the following considerations: (1) The whole equipment has to be carried on pack animals. (2) The average load for a battery mule is about 280 ℔, including 65 ℔ of saddle and equipment. A few specially selected gun-mules can carry about 40 ℔ more, or 320 ℔. In Spain and Italy, where exceptionally fine mules are available, some of the mountain battery loads amount to 375 ℔. (3) The loads must be short, the length being limited by that of the neck of a mule. If possible no part of the equipment should be more than 4′ 6″ long. (4) The equipment must, therefore, be subdivided into component parts such that no part weighs more than 320—65 or 255 ℔, and these parts must be so designed as to be quickly assembled. (5) The number of parts into which the equipment may be subdivided is either four or five. British mountain batteries have five gun and carriage mules, and yet they come into action and fire the first round within one minute. Other nations mostly divide the equipment into four parts only, and use rather heavier loads than is in England considered consistent with activity on a hillside (6) Mountain guns are usually provided with shafts to enable them to be drawn instead of being carried when travelling along a road.

On a 5-mule basis the total weight of gun and carriage carried amounts to 10 cwt. or more than half the weight of a field gun. But the power obtainable is not commensurate, being in practice limited by the weight of the gun itself, which is restricted by the carrying power of the transport animals. In B.L. mountain equipments this difficulty has been got over by carrying the gun in two parts, which are screwed together on coming into action.

In the British service the 7 pr. R.M.L. of 400 ℔, the original “screw gun,” was superseded in 1900 by the 10 pr. B.L., also in two pieces. A quick-firing mountain gun has since been introduced (1907).

In modern mountain equipments, such as the Schneider-Danglis gun adopted by Russia, the gun is not divided across the bore but is lightened for transport by removing the breech-piece and breech-block, which are carried separately. These guns fire a shell of 14·3 ℔ with M.V. of 1100 f.s.

When the gun is in one piece, the equipment naturally divides itself into four parts, namely the gun, cradle, trail and axletree and wheels. When a long jointed trail is used, as in the Krupp Q.F. mountain equipment, the point of the trail is carried with the wheels, which form a light load. In addition to this the folding shield with ammunition forms a fifth load. The shield need not, however, be brought up till after the gun has opened fire.

Since the length of a mountain gun in one piece may not exceed 4 ft. 6 in., the calibre has to be comparatively large to get the necessary power, and is usually 75 mm. or 3 in. The weight may not exceed 255 ℔. A short breech action such as the swinging block or the eccentric screw is preferred. The sights must be of simple pattern; the independent line of sight is too complicated for mountain work. But it is most desirable that the sight-socket should be capable of being cross-levelled to eliminate the error introduced by difference of level of wheels. Except in the French gun, the recoil gear and running-up springs are similar to those used in Q.F. field guns. In the Krupp mountain equipment the gun does not slide directly on the cradle guides, but a steel forging called a sleigh is interposed. This forms a sliding cover to the cradle, and protects the guides. On coming into action the gun is dropped into the sleigh and secured by a keyed lug. The trail of a Q.F. mountain gun has to be from 6 ft. to 7 ft. long to keep the gun steady. It is either carried in two pieces (Krupp) or is hinged and folded (Ehrhardt). The spade is similar to that used with field guns. The wheels are of wood, about 3 ft. in diameter. The elevating gear is a plain screw. The gun and cradle traverse on a vertical pivot about 3 degrees each way. A shield high enough to protect the gunners kneeling weighs up to 1 cwt., and is carried in two pieces.

The Krupp mountain gun, fig. 68 (Plate IV.), may be taken as an example of ordinary practice. The gun is seen mounted on the sleigh, which slides to the rear on the cradle when the gun recoils. The cradle is pivoted vertically on a saddle mounted on horizontal trunnions between the trail brackets; the rearward extension of the saddle forms the traversing bed and is supported by the elevating screw. The foresight and arc sight are attached to the cradle. Near the middle of the 7-ft. trail are seen the seats for the laying and loading numbers. The trail is divided immediately in rear of the seats. The calibre is 2·95 in., the gun fires a shell weighing 11 ℔ 10 oz. with a muzzle velocity of 920 f.s. The weight in action is 820 ℔, without shield.

The French 1907 mountain gun differs markedly from other types in that the carriage is constructed with differential recoil gear as described above. There is no hydraulic buffer, and the whole of the recoil-energy is absorbed by the springs. The gun is held in the recoil position by a catch, and when loaded and released it is fired automatically by a tripper on the cradle. The calibre is 2·65 in., and the shell weighs 11 ℔ 10 oz.

.—H. A. Bethell, Modern Guns and Gunnery (Woolwich, 1907, 3rd edition, 1910); Kenyon, F.A. Material on the Continent (R.A. Institution, Woolwich, 1905); Greenhill, “The Dynamics of Gun Recoil,” The Engineer (23rd August 1907); v. Roskoten, Moderne Feldkanonen (Oldenburg, 1906); Rohne, Progrès de l’artillerie de campagne moderne (Paris, 1906), Challéat, Théorie des affûts à deformation (Paris, 1906), Siacci, Balistique extérieure; Witzleben, Feldgeschützfrage in Portugal (Dresden, 1906); Castner, “Development of Recoil Apparatus,” Journal U.S. Artillery (1904); and Der Erfolg des stdndigen Rohrn'icklaufs bei Feldhaubitzen (Frauenfeld, 1906); v. Reichenau, Munitionsausrüstung (Berlin, 1905). Shrapnels et boucliers and L’Obusier de campagne moderne (Lucerne, 1906), Bahn. Die Entwicklung der Rohrrücklauf-Feldhaubitze (Berlin, 1907),

Heavy Field Batteries.—Since the days of Gujrat and Inkermann the value of heavy metal in the field has been recognized, at all events in theory, but it was mainly due to the South African war that “heavy” batteries have become a component part of modern armies. Guns heavier than field guns have formed part of the equipment of the Indian army for many years.