THE 155-MILLIMETER G. P. F. GUNS.
The reproduction in the United States of the French 155-millimeter G. P. F. (the French designation) gun presents much the same story as that of the howitzer of equal size—a story of difficulties in translating plans, writing into them the precision of finishing measurements that the French factory usually leaves to the skill of the mechanic himself, difficulties in finding manufacturers willing to undertake the work, and then of providing them with suitable raw materials and machinery, and, above all, of locating the necessary skilled mechanics.
This strange, big monster of a weapon is of rugged design. The entire unit weighs 19,860 pounds. The gun has the extremely high muzzle velocity of 2,400 feet per second, a rate of propulsion that throws the 95-pound projectile 17,700 yards, or a little more than 10 miles.
The wheels of the carriage have a double tread of solid rubber tire. By an ingenious arrangement a caterpillar tread can be applied to the wheels in a few minutes whenever soft ground is encountered.
The center of gravity of the unit is low. The wheels are of small dimensions and the cradle is trunnioned behind in such a fashion as to reduce the height of the cannon. The carriage has a split trail, which allows for a large clearance for recoil at a high elevation and a large angle of traverse. The carriage when traveling is supported on semielliptical springs, as is also the carriage limber.
Two large steel castings make up the carriage of this unit. The bottom part of the carriage is supported by the axle, which carries the two sections of the split trail upon the hinge pins. The top part of the carriage is supported by and revolves upon the bottom carriage and carries in trunnioned bearings the recuperator. The principal difficulty in carriage manufacture was to obtain in this country the extremely large steel castings of light-section, high-grade steel.
The carriages, 1,388 in number, were ordered in November, 1917, from the Minneapolis Steel & Machinery Co. The first delivery of carriages was made in August, 1918, and in the last week of October they were being turned out at the rate of seven a day. Up to the armistice date 370 had been produced, of which 16 had been sent overseas.
We also placed orders in France for 577 of these carriages, of which 216 had been completed upon the signing of the armistice. The American monthly rate of production of carriages in October was 162.
The 155-millimeter gun itself is far from being simple to manufacture. It is of considerable length and is built of a number of jackets and hoops to give the required resistance to the heavy pressures exerted in firing, this being a high-velocity gun. Except for a slight change in the manner of locking the hoops to the jacket, our gun is identical with that of the French.
Orders for 2,160 cannon were given to the Watervliet Arsenal and the Bullard Engineering Works, at Bridgeport, Conn., in November, 1917. The Bullard Engineering Works had to construct new buildings and to purchase and install special equipment, and the Watervliet Arsenal had to extend its shops and also purchase and install much additional machinery—a job that took time at both places.