2. The effective range of machine guns is the same as that of the rifle; they are therefore not suited for employment in place of artillery. On the other hand, the effect of machine-gun fire at effective infantry and close infantry ranges is very great, and at close infantry ranges it may, with favourable conditions, be annihilating. Machine guns are very suitable for the development of covering fire within the limits of effective rifle range. They can accompany the troops to which they may be attached over any country. 3. The action of the mechanism is liable to temporary interruption by jams. Machine guns should not therefore be used singly under normal conditions. They are organised in sections of two guns, which should rarely be broken up. 4. Machine guns are essentially weapons of opportunity. The expenditure of ammunition involved and the nature of the mechanism make long periods of rapid fire unsuitable. The power of the gun is best used to develop unexpected bursts of fire. _The Organisation and Training of Infantry Machine-Gun Sections_ 1. The strength and composition of a machine-gun section are shown in War Establishments. An infantry machine-gun section is an integral portion of an infantry battalion, but two or more sections may be brought together by the brigade commander and used under the command of a brigade machine-gun officer. The two non-commissioned officers and twelve privates shown in the establishment will be trained as first-class machine gunners. Two non-commissioned officers and twelve men will be trained, as opportunity offers, as second-class machine gunners to replace casualties among first-class machine gunners. 2. A subaltern officer, other than the assistant adjutant, will be selected in each battalion to command and train the machine-gun section, under the orders of the commanding officer. Should a brigade commander desire to train the machine guns of his brigade to act together when massed, an officer, who is not the machine-gun officer of one of the battalions of the brigade, may be selected to supervise the firing practice and to conduct the brigade training of machine-gun sections. 3. Officers, non-commissioned officers, and men detailed for machine-gun training should be changed as little as possible; the two non-commissioned officers and twelve men trained as first-class machine gunners will fire the practices prescribed in the Musketry Regulations with one of the companies of the battalion,[67] but will at other times be at the disposal of the machine-gun officer for instruction. 4. Details as to the mechanism of the gun, and the drill of machine-gun sections are contained in the handbook of the gun. Instructions as to the course of firing are contained in the Musketry Regulations.