McMahon was appointed to the staff again in June 1905 when he was appointed chief instructor at the army's School of Musketry in Hythe, Kent. As chief instructor in 1907 he foresaw the future of warfare and recommended that each infantry battalion be allocated 6 machine guns. This recommendation was rejected and he instead instituted reforms of rifle training. Under McMahon all infantrymen were required to be able to fire 15 aimed shots in a minute, a practice that was enshrined in the "Musketry Regulations of 1909". This became known as the "mad minute" and proved highly effective during the August 1914 Battle of Mons. it is said that German soldiers coming up against such rapid fire presumed that they were facing a battery of machine guns.