An interesting fact in connection with the production of shell for the 6-inch mortars is that they were built principally by American makers of stoves. The 6-inch mortar-shell bodies were of cast iron instead of steel, and thus were adaptable to manufacture in stove works. Each shell weighed 40 pounds without its explosive charge. Such shell were used at the front for heavy demolition purposes.

The contracts for these shell were placed in March, 1918. The Trench Warfare Section was immediately called upon to secure favorable priority for the pig iron required for this purpose. The various stove works did not have the necessary machinery for building these shell, and so a special equipment in each case had to be built. At the tests the first castings which came through the foundry were found to leak, and this required further experiments in the design, holding up production until July, 1918.

Because of the many troubles encountered in this work the various stove makers in the summer of 1918 formed an association which they called the Six-inch Trench-mortar Shell Manufacturers' Association. This association held monthly meetings and its members visited the various plants where shell castings were being made. The United States Radiator Corporation, the Foster-Merriam Co., and the Michigan Stove Co., were especially active in improving methods for making these shell.

The various concerns producing 6-inch mortar shell and the amounts turned out were as follows:

Foster Merriam Co., Meriden, Conn.33,959
U. S. Radiator Corporation, Detroit, Mich.240,700
Globe Stove & Range Co., Kokomo, Ind.17,460
Rathbone, Sard & Co., Albany, N. Y.97,114
Michigan Stove Co., Detroit, Mich.100,000

The following concerns shortly before the armistice was signed received contracts for the production of 6-inch mortar shell, orders ranging in quantity from 50,000 to 150,000, but none of these concerns started production:

It was not until July, 1918, that the plans were ready for the 4-inch Newton-Stokes trench mortars. The American Expeditionary Forces estimated that they would require 480 of these weapons. A total of 500 drawn barrel tubes was ordered from the Ohio Seamless Tube Co., of Shelby, Ohio. This concern was able to ship one-fifth of its order within 10 days after receiving it. The barrels were sent to the Rock Island Arsenal for machining. The Crane Co., of Chicago, held the contract for building the bases, tripods, spare parts, and tools, and also for the assembling of the completed mortars. This factory was already equipped with tools for this work, since it had been building similar parts for 3-inch mortars. Consequently, the Crane Co., in August, almost within a month of receiving its contract, was producing completed 4-inch mortars and sending them to the Rock Island Arsenal for proof firing. The Ohio Seamless Tube Co. reached a high daily production of 83 barrel forgings per day; the Rock Island Arsenal, 10 machined barrels per day; and the Crane Co., 19 assembled mortars per day.