If the heavy machine gun defines one end of the machine gun spectrum then the support rifle defines the other … or perhaps it's more like an assault rifle with delusions of grandeur. Very often the problem is that a support rifle tries to be both a rifle and a machine gun and ends up doing neither job well.
Typically the support rifle is a modified assault rifle which has been upgraded … sometimes very slightly … to provide a weapon intended to generate covering and supporting fire for an infantry section or half section. These weapons may have any of: a bipod, a heavier barrel, an extended barrel, a quick change barrel, a larger magazine or a rear grip. Too many of those features and it starts to look like a light machine gun instead - and indeed many 1930s LMGs, such as the Bren/L4, the Chatellerault and the Madsen look a lot like support rifles to modern eyes. Usually the support rifle will have little or no beaten zone1, retaining rifle standards of accuracy which reduces their ability to lay down area fire like a true machine gun but can be very useful for point suppression. This category also includes experimental weapons like the BAR.
The utility of the support rifle is something of a contested issue and they tend to appear and disappear from military inventories every few decades. The main problem is with the volume of fire they produce - the weapon generally fires from a normal rifle magazine, which is good for compatability within the section but poor for sustained fire and barrel upgrades are rarely heavy enough to stand the volume either. The lack of a beaten zone doesn't help either - area suppression is an important duty for the section gun and point suppression is an over specialised and not entirely substituable alternative.
Examples of the purpose built support rifle include the M14E2, the L86A2 and, arguably, the RPK.
A newer role for the support rifle is found amongst armies that use a bullpup assault rifle as standard issue (like the British Army's L85) … the support rifle is a longer barrelled version used to provide longer ranged fire. To continue the L85 example the support variant (the L86) was originally intended as an LMG substitute and a direct replacement for the L4, in which role it proved inadequate, but is now used in the extended range role.
Game and Story Use
- Some of the weapons used in this role have been shockingly bad - the L86 was inadequate, the M14E2 had a tendency to shake itself to pieces and the Chauchat (a WW1 LMG that is best - or at least most politely - classified as a support rifle) was so bad as to be worthy of some kind of award. Pity the PC who is issued one (in a military campaign) or accquires one on the assumption that it's a machine gun.