The FN MAG Machine Gun: M240, L7, and other variants (Weapon) by Chris McNab

Author:Chris McNab [McNab, Chris]
Language: eng
Format: epub
ISBN: 9781472819697
Publisher: Bloomsbury Publishing
Published: 2018-07-25T23:00:00+00:00

The basic message of all these figures is that an enemy anywhere within 3,000m (3,281yd) downrange of a MAG-type weapon needs either to be well protected behind cover, or well out of the line of fire. For the gun team, however, there is also the issue of delivering their fire in a sustained way. Of the total amount of energy expended when a bullet is fired from a gun, only about 30 percent is actually imparted in the form of kinetic energy behind the bullet. Even with a thick machine-gun barrel fitted, any sort of sustained fire will quickly heat up a barrel until it can reach temperatures in excess of 750°F. Should temperatures climb higher, to around 930°F, then the barrel can start to experience structural damage, “burning out” the rifling and affecting the barrel’s accuracy. The other problem is that of “cook off,” in which cartridges are detonated purely by the excessive heat in the chamber setting off the propellant. Such a situation is naturally dangerous to the users.

With the MAG, there are two ways in which the user can control barrel heating: controlled and sensible patterns of fire, and barrel change. The former is the product of good training in the form of emotional discipline (to avoid overexcitement producing excessive bursts in combat conditions). A useful guide to what is appropriate, depending on the target type, can be found in the British Army manual Infantry Training Volume 1: The General Purpose Machine Gun (Light Role). It recommends an initial burst of 3–5 rounds, with the gunner taking care to observe the fall of shot as closely as possible, with both eyes open, before adjusting the sights or aim to allow for range, wind, and other factors. Every fifth round should be tracer. The gunner should then resume firing at a rate of 25rd/min; burst length should depend on the nature of the target, the range, and other variables. Rapid fire – specified as being around 100rd/min (no more than that during training), and defined as the maximum rate of fire at which accuracy can be maintained – should be reserved for particular targets or situations, in order to avoid overheating the barrel, incurring dangerous stoppages, or wasting ammunition. If rapid fire is required, the gunner should take advantage of any lull to unload the weapon, cock it, and raise the cover to facilitate cooling (MOD 1966: 29). The manual mentions the alternating use of one eye/both eyes for aimed firing and observed impact, and the utility of longer bursts for tackling AFVs (the multiple rounds raising the possibility of shattering the vehicle’s external equipment or passing through a vision slot to hit an occupant). But the central message is clear: fire should ideally be controlled in 3–5-round bursts, with spaces in between for cooling. In extremis, the gunner can increase the rate of fire to bursts of 5–8 rounds, or even longer if the situation demands it, but this is not to be recommended.

Modern US armed services advice relating to the M240 gives similar procedural guidelines.

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