A little while back I posed the question of how firearms are classified. Lacking any clear cut publication, I have perused the gun associated volumes and offer the following parameters. These are my own deductions and definitions, using primarily U.S. Army guidelines, but also European and U.S. civilian parlance as well.
First of all, a few definitions of terms is in order:
Automatic fire~ a weapon that fires when the trigger is activated and continues to fire as long as the trigger is held back.
Semi-automatic fire~ a weapon that fires one shot with each pull of the trigger, without any manual manipulation being required.
Controlled burst~ a weapon that fires when the trigger is activated and continues to fire a limited number of shots while the trigger is held back.
Selective fire~ A weapon that allows either automatic or semi-automatic fire with a selector switch.
Gun~ in U.S. military parlance, the term "gun" implies a crew served weapon, as opposed to individual weapon, usually fired from a mount.
Small Arms~ weapons of 15mm or smaller. Larger caliber classed as cannon.
[B]Small Arms Classifications[B]
Assault Rifle A short, Handy shoulder weapon, capable of select fire with usually a high capacity magazine. The ammunition is usually shorter and less powerful than the standard infantry cartridge, for close range use. May be fitted with a bayonet.
Automatic Rifle A shoulder fired weapon capable of automatic fire, magazine fed firing the standard infantry round. Usually fitted with a carrying handle and bi-pod. Also called machine rifle or light machine gun.
Battle Rifle The standard infantry rifle, a shoulder fired magazine rifle. Usually fully stocked and of robust construction. The cartridge defines the standard infantry cartridge, and is capable of hitting man-sized targets at ranges of 500~600 yards, and delivering fatal wounds at ranges of 1000 yards. Has provision for bayonet and/or grenade launchers.
Carbine A shoulder fired magazine rifle taking the standard infantry cartridge, often times a reduced size and lighter version of the Battle Rifle.
Heavy Machine Gun(1) An automatic belt fed machine gun of standard infantry caliber, often water cooled, fitted with finely adjustable sights and mounted on a heavy mount fitted with micrometer adjustable traversing and elevating mechanisms. It is used to provide overhead covering fire for advancing troops, or to engage long range enemy troop concentrations.
Heavy Machine Gun(2) A heavy crew served machine gun, belt fed and fired from a mount, taking a cartridge of larger caliber than the standard infantry round. Used against light armored vehicles, aircraft, and personnel in heavy jungle growth.
Light Machine Gun An machine gun either belt fed or magazine fed firing the standard infantry cartridge, fired from a light tripod or bi-pod. Automatic rifles and machine rifles have often been classified as Light Machine Guns.
Light Rifle A short, lightweight, handy shoulder weapon, magazine fed, taking a pistol cartridge smaller than the standard infantry cartridge. Usually a secondary weapon. (Note: The U.S. Carbines M1 and M2 fall into this class.)
Machine Carbine A short, handy, magazine fed shoulder weapon, usually select fire, with a high capacity magazine, using a rifle cartridge shorter and less powerful than the standard infantry round. I believe this term is of British origin.
Machine Pistol Originally an automatic pistol capable of automatic fire fitted with a shoulder stock. The term now, in Europe, is applied to short, handy shoulder weapons of pistol caliber capable of automatic fire. American practice is to designate these as Sub Machine Guns.
Machine Gun An automatic weapon fired from a mount and belt fed. The machine gun uses the power of the fired cartridge to function the feeding, firing, and ejecting cycles, as opposed to motor driven rapid fire weapons.
Machine Rifle An automatic shoulder fired weapon taking the standard infantry cartridge, magazine fed, usually fired from a bi-pod mount. Also referred to as a light machine gun or automatic rifle.
Sub Machine Gun A short, handy shoulder weapon, magazine fed firing a pistol caliber cartridge, capable of automatic fire. Usually has a high capacity magazine of straight or drum configuration. European practice is to designate these as Machine Pistols.
These are entirely my own interpretations and deductions gathered from many publications over the years. Your comments and/or corrections are welcome and solicited.
(My classification of the .30 Carbine round as a pistol cartridge may raise some hackles. However, it does fit that category, as a short, straight, rimless cartridge.)