He transferred out of the Navy, due to chronic sea sickness, and was assigned to the Army Coast Artillery Corps.

In 1916, the Hotchkiss M1909 Benét–Mercié machine gun was in general use with the U.S. Army and was seeing action during the Punitive Expedition against the bandit Pancho Villa.

In 1919, at age 31 and holding the acting rank of lieutenant colonel, Hatcher was named commanding officer of Springfield Armory in Massachusetts.

As Chief of the Small Arms Division in the United States Army Ordnance Department and the Assistant Commandant of the Ordnance School before and at the beginning of World War II, Hatcher worked closely with Springfield Armory as an engineering trouble-shooter in resolving early production issues associated with the early iterations of the M1 Garand rifle.

In the latter work, he introduced the Hatcher Scale, probably the first attempt to determine the stopping power of a handgun round by a formula.