The railway carriages could elevate the guns to 43 degrees, but elevations over 15 degrees required excavation of a pit with room for the gun to recoil and structural steel shoring foundations to prevent caving of the pit sides from recoil forces absorbed by the surrounding soil. The trains moved cautiously because axle loading under the gun barrels was while French railways were designed for a maximum of . These axle journals overheated at speeds of more than per hour. After reaching its intended firing site and constructing the recoil pit, each gun could fire about two shells per hour. One of these guns was retained after the War as an ammunition test gun at the Dahlgren Weapons Laboratory until all United States battleships with 14"/50 guns were scrapped shortly after World War II. The gun was then placed on display outside the U.S. Navy Museum at the Washington Navy Yard. Baldwin constructed six similar gun carriages and two of an improved Mk II type designed to permit firing the gun at all elevation angles without transferring weight to a separate foundation. These eight guns were completed too late to see combat, and were designated the 14-inch M1920 railway guns. Some were later stationed through World War II in special coast defense installations at San Pedro, California, (near Los Angeles) and in the Panama Canal Zone where they could be shifted from one ocean to the other in less than a day. Improved carriages were designed to allow their transportation to several fixed firing emplacements including concrete foundations where the railway trucks were withdrawn so the gun could be rapidly traversed (swiveled horizontally) to engage moving ship targets. After the American entry into World War I on 6 April 1917, the U.S. Army recognized the need to adopt railway artillery for use on the Western Front. No US railway guns existed at that time. Due to low production and shipping priorities, the Army's railway gun contribution on the Western Front consisted of four U.S. Coast Artillery regiments armed with French-made weapons. Three additional railway gun regiments were in France, but did not complete training prior to the Armistice, and they did not see action. Other Coast Artillery units also operated various types of French-, British-, and American-made heavy artillery. The Army also converted some of the numerous coast artillery weapons to railway mounts. A total of 96 8-inch guns (including