war iO'5-cm. (4-13-111.) medium gun was 36 cals. long and ranged 12,- 200 yd. Their 1914 pattern was 35 cals. long, range 14,300 yd.; and their 1917 pattern was 45 cals. long, range 21,300 yd. with false cap. It was on a field carriage of simple construction, with 4 ft. 4-m. wheels, resembling an enlarged field gun. It had rear trunnions, variable recoil (95-155 cm.), air recuperator and pivot traverse. The carriage gave 45 elevation. The weight was about 31 tons.
In the World War, all parties used medium guns of lo-cm. (4-2- in.) and 12-cm. (47-in.) calibre. These were largely not model guns belonging to siege trains and fortress armaments but some powerful naval guns and also some new models (e.g. the French iO5-mm. of 1913) were amongst them. Since the war a few types have been brought out, but for the reason mentioned below the history of the medium gun seems to be closed.
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FIG. 23. British 6o-pdr. gun.
The French (St. diamond) carriage for 4>7-in. guns or 6' I -in. how- itzers is noteworthy as a successful attempt to simplify equipment by using one pattern of wheeled carriage which will take either a medium gun or a heavy howitzer. The carriage has hydro-pneumatic recoil gear of the " floating " piston class. The recoil is controlled, i.e. automatically shortened at high elevations to prevent the breech of the gun from striking the ground. This is effected by throttling the passage through which the liquid passes from the buffer to the compressed-air reservoir, by means of a valve actuated, through the left cradle trunnion, by a cam attached to the carriage. The relative motion of the cradle with regard to the carriage, as the gun is elevated, partly closes the valve. This is the gear which has been adopted for several of the new U.S.A. equipments, as mentioned above. It is simple and efficient, and is better adapted for mass production than the pattern in which the recoil is controlled by revolving the buffer piston.
FIG. 24. German lo-cm. gun, 1914.
The 4-7-m. gun and 6-i-in. howitzer made by the St. Chamond firm have the Canet " revolving block " breech action and have rear trunnions, the forward preponderance being held up by a pneumatic balance spring. In other respects the wheeled carriage is of the ordinary construction. Since the gun, or the howitzer, weighs only 3-46 tons in action, it can be transported on its own wheels by a team or a tractor. However, to increase its mobility, it is usually transported in two loads, the gun travelling on a special wagon.
Although medium guns have been of great service in the past, it seems doubtful whether any more of them will be made. They repre- sented the maximum power, subject to the limitations of horse draught, that was compatible with mobility sufficient to march with an infantry division. With the advent of mechanical traction, they are likely to be superseded by the far more powerful 6-in. gun.
Medium Howitzers. During the period of trench warfare, the principal weapon employed by both sides was the 6-in. howitzer, throwing a shell of 95 to 100 Ib. This was capable of penetrating the strongest artificial cover commonly met with in the trenches, and nothing short of a semi-jjermanent concrete structure was proof
against it. Practically all belligerents employed weapons of this class, both old models (adapted- to new mountings or left on their old carriages) and new. In 1914 the British had none of these pieces except a few of the old siege howitzers described and illustrated at 20.224, b ut ^he ^' n ' Q-F- howitzer designed in January 1915 began to be issued in the latter part of the same year, and by the end of the war 3,633 of these had been delivered. It proved a serviceable weapon, though far inferior in power to those made since the war, as its weight was restricted by the limitations of horse draught, and was only 86 cwt. It ranged 10,000 yd. with a loo-lb. shell, or 11,600 yd. with the streamline shell afterwards introduced. The carriage was of simple construction with a long cradle. Future equipments of this nature will be made with S split trail to avoid the delay in- curred by traversing such a heavy piece.
FIG. 25. German lo-cm. gun, 1917.
The French in 1914 had only 105 mobile 6-in. howitzers. These were of the Rimailho pattern, designed by Commandant Rimailho, who like Deport had been one of the creators of the 75-mm. gun This piece was remarkable in its day as being the first medium howitzer designed to be drawn across country by a team of horses at a trot. This degree of mobility was secured by conveying the howit- zer itself on a special light wagon, while the carriage travelled empty. This wagon formed a slide which could be adjusted in prolongation of the cradle, so that the piece could be shifted from one to the other by means of a winch, an operation which took only ten minutes. Other features which were then novel were a semi-automatic breech mechanism actuated by the recoil, an automatic loading system in which the shell and cartridge were driven home by the breech block, elaborate sight mechanism, and rear trunnions with a pneumatic balance spring. The wagon with the piece weighed 2-75 tons, and the
FIG. 26. British 6-in. Q.F. howitzer, 1915.
empty carriage 2-5 tons. The extreme range was 6,500 yd., as the piece itself was an old model.
As the Rimailho was not sufficiently powerful, and as only 105 existed, Schneider and St. Chamond weapons of the same class were brought in to replace it. The powerful Schneider 155-mm. (6-i-in.) howitzer throws a 95-lb. shell, M.V. 1,500 f.s., to a range of 13,300 yd. The peculiarity in its construction is the counter- weight on top of the breech. This was added in order to enable the makers to get a greater length of the piece forward of the trunnions while maintaining a breech preponderance. In ordinary times they might have put in a pneumatic balance spring, 1 but in war-time the simpler expedient was preferred.
1 Balance springs and pneumatic equilibrators are introduced to take the weight of the gun and cradle when trunnioned behind the centre of gravity. This rear trunnioning is necessary with long-recoil high-elevation guns because, if the cradle were on central trunnions so as to balance the gun, then, when elevated, the breech would strike the ground on recoil. But this gives the gun a heavy muzzle preponderance which has to be balanced. The usual method was
