As the name suggests, these are the biggest and heaviest of the machine gun class.
Man-portable only when dismantled they are heavy weapons that blur the boundary between small arms and ordnance - by consensus they are always above rifle calibre (so generally >9mm) but below 20mm which is the generally accepted lower limit for an automatic cannon (and therefore ordnance).
An HMG is usually belt fed (although it may be fed from a hopper, particularly aboard ships or aircraft) and may or may not have features like cooling and quick change barrels. Their long range often leads to the fitting of fairly high quality sights.
Examples of HMG would include the US M2 Browning (.50CAL), the Soviet DShK (12.7mmWARPAC) and the 15mm BESA MGs used in some British AFV during WW2.
Early HMG were often found attached to warships in an anti-topedo boat role, although some of these are automatic cannon by modern definitions (e.g. the 1 pounder Maxim Gun beloved of the Royal Navy (37mm calibre!)). Other typical HMG roles are low level air defence, anti-vehicle work and long ranged support.
Game and Story Use
- HMG fire goes through most of the things that infantrymen will try to hide behind - walls, trees, earth bunds and lightly armoured AFV. If you need to get your PCs moving, this is an excellent thing to have flush them out.
- Some of the HMGs on the market are surprisingly accurate and can deliver precise, long ranged fire if they can be persuaded to fire only one shot at a time.