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The US Army "System of Mobile Artillery"
Between 1902 and 1915, the Ordnance Department of the United States Army developed a system of mobile artillery pieces based upon two ideas. The first of these called for the creation of a family of projectiles, each of which would weigh twice as much as its predecessor. (The lightest of these shells would weigh 15 pounds. The heaviest would tip the scales at 120 pounds. In between these two extremes, there would be a 30-pound shell and a 60-pound shell.) The second idea called for the design of a gun and a howitzer for most of the shells in the series.
Once realized, this system would provide the Army with three sets of field pieces, each of which was composed of two different weapons of much the same weight. The first set would consist of a 15-pounder light field gun and a 30-pounder light field howitzer. The second set would be made up of a 30-pounder field gun and a 60-pounder field howitzer. The third set would comprise a 60-pounder heavy field gun and a 120-pounder heavy field howitzer.
In addition to the three sets of field pieces, the system would also include a 15-pounder pack howitzer. Frequently (but incorrectly) described as a “mountain gun,” this would be a howitzer small enough to be broken down into a series of loads, each of which was light enough to be carried by a mule. (The rule of thumb for such loads is that each should not weigh more than 200 pounds.)
Between 1902 and 1915, the Ordnance Department built prototypes for all members of the “system of mobile artillery.” In the same period, it put two members of the family, the 3-inch light field gun and the 4.7-mm heavy field gun, into serial production.
Upon the entry of the United States into the First World War, the Ordnance Department made plans to for the mass production of all guns and howitzers of the “system of mobile artillery.” However, by the end of 1917, this plan had been replaced by a program to arm most of the field artillery batteries of the American Expeditionary Force with French weapons, particularly the famous “French 75” (75mm field gun Model 1897) and the Schneider heavy field howitzer (155mm Model 1917.) Indeed, the only piece from the “system of mobile artillery” to see service in France was the 4.7-inch heavy field gun. (The 3-inch light field guns were used to arm field batteries serving on the border with Mexico.)
Sources: Most of the figures in this table come from the following official publications of the U.S. Army Ordnance Department, all of which were published in Washington by the Government Printing Office: Handbook of Artillery, (1925), pages 284 and 316; Handbook of the 3-inch Gun Matériel, Model 1902 (1917), pages 13 and 60; Handbook of the 3.8-inch Gun Matériel (1917), pages 9 and 17; Handbook of the 3.8-inch Howitzer Matériel, Model 1915 (1917), pages 11 and 37-38; and Handbook of the 4.7-inch Gun Matériel (1917), pages 9 and 34. Figures for the 4.7-inch howitzer and 3-inch mountain howitzer come from two anonymous publications of the Bethlehem Steel Company: Mobile Artillery Material (South Bethlehem: M.S. Grim, 1916), pages 34-35 and 3-inch Mountain Gun and Carriage, Mark B (South Bethlehem: M.S. Grim, 1916), pages 6 and 10. Figures for the 6-inch howitzer come from 108th (2nd Pennsylvania) Field Artillery Regiment, Field Artilleryman’s Guide (Philadelphia: P. Blakiston’s Son, 1918), page 238.
For contemporary descriptions of the US “system of mobile artillery”, see the many books, articles, and locally published lectures produced by Oliver J. Spaulding, Jr. during this period, particularly The New Field Artillery Materiel … Its Characteristics and Powers (Fort Leavenworth: Staff College Press, 1905), pages 14-16; Artillery Weapons, (Fort Leavenworth: Infantry and Cavalry School, 1907), pages 18-21 and Notes on Field Artillery for Officers of All Arms (Fort Leavenworth: U.S. Cavalry Association, 1914), pages 53-58.
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