Innovation and Adaptation

Indirect Machine Gunnery for the Motorised Battalion

By Chris Thorburn August 19, 2019


Imagine having the ability to direct suppressive fire on to a target from distance without ever revealing the location of your machine guns to the enemy.

In the Australian Army this capability is a reality. In the infantry, Direct Fire Support Weapons (DFSW) soldiers are charged with providing the suppressive fire necessary for manoeuvre elements to close with and kill the enemy.

At present, extended range machine gunnery (ERMG) is a specialist skill that takes weeks to teach to a trained infantryman, and as yet the Army has not worked out how to achieve ERMG from a mounted firing platform.

My idea seeks to address this capability gap.

How? By transforming a machine gun mounted in a protected weapon station (PWS) into an ERMG.

This would enhance Army’s ability to manoeuvre in two ways. First, it would turn any vehicle equipped with a PWS into a mobile indirect fire support platform. Second, it would increase the survivability of motorised combat teams and battle groups by allowing PWS machine guns fitted to Bushmasters and Hawkei Protected Mobility Vehicles to be employed from defilade.

Best of all, by using existing technology this capability would require very little investment to establish and could be easily integrated into the current PWS course.

In short, the capability would provide an interim fire support solution to the motorised battalions until future technologies such as loitering munitions are acquired.

Principles of indirect machine gunnery

To understand how indirect machine gun fire could be achieved from a vehicle platform, it is best to start with an explanation of how DFSW soldiers establish fire positions.

A dismounted DFSW section in an ERMG role is composed of two machine guns mounted on tripods. Each gun is equipped with four spare barrels, and a C2 sight and post.

Put crudely, the purpose of an ERMG drill is to turn a machine gun into a compass. This is done by levelling and paralleling the section or platoon’s guns, fixing each gun to a known reference point (the post), and adjusting the scales of the C2 sight. Adjusting the scales of the sight ensures that bearings taken from the gun’s location on a map align with the actual direction of the gun’s barrel on the ground. Once the scales have been adjusted, the gun will align with a target once a bearing has been inputted into the sight, and the gun has been brought on to post.

This part of the drill ensures that the gun is pointing the right way.

The purpose of the second aspect of the drill is to get the gun firing at the correct range. To do so, a DFSW section or platoon commander measures the distance between himself and the target and the difference in elevation between his guns and the target. Because the guns are firing from a fixed and stable firing position (a tripod) the trajectory of the rounds is fixed. Because the trajectory of the round is fixed, the section commander is able to use a predicted data table to calculate the elevation required to achieve rounds on to target.

Skilled and well-practised gun crews can set up a gun in this manner in six minutes and switch targets in less than thirty seconds. These are impressive skills, but skills that could easily be automated by a fire control system (FCS).

Proposed system: automated indirect Protected Weapon Stations (PWS)

Three pieces of equipment are required in order to achieve accurate indirect fires from a mounted platform.

First, a stabilised weapons platform that is able to level and adjust the bearing and elevation of a gun automatically and stable enough to guarantee the shape and size of a beaten zone.

Second, a FCS that is able to mimic the drills of a human DFSW crew.

Third, a heavier barrel to sustain the rate of fire required, or at least a barrel rack that allows the operator to rotate hot barrels within the vehicle.

To use such a system, a soldier would simply need to input a target grid and his or her location, load and fire the weapon, and change barrels and fix stoppages as required.

As the principles of machine gunnery are weapon agnostic, any weapon that is capable of forming a beaten zone could be mounted to the system provided that the ballistic character of that particular weapon was inputted into the system. Such a system would transform the PWS from a direct fire weapon system into an indirect platform capable of achieving fires out to a significant distance with the .50 calibre heavy machine gun (HMG), and the MK47 automatic grenade launcher (AGL).

Tactical applicability

I am not proposing that such a system would replace DFSW Platoons within motorised battalions or that such a system would turn the Bushmaster or Hawkei into a fighting vehicle.

Vehicles will never be able to achieve surprise in the same way that dismounted DFSW soldiers can.

Moreover, due to basic geometry the closer a dismounted element is able to get to a target, the longer they are able to suppress an enemy position. Therefore, only dismounted call signs are able to provide the amount and quality of suppression necessary for a deliberate dismounted attack that achieves break-in and successfully exploits an enemy’s position.

Most manoeuvre commanders would also accept that the best way to conduct motorised operations is for dismounted call signs to clear the ground whilst their vehicles remain to the rear. However, in situations where speed is of the essence troops may be forced to remain mounted in their vehicles.

In such instances, whether withdrawing or in the pursuit, the ability for vehicles to remain behind cover whilst troops dismount, and then manoeuvre in support of their own troops, is a desirable capability. This is particularly the case where a motorised combat team or battle group is unsupported by armoured call signs who would ordinarily be able to guard the main body’s flanks.

An indirect weapons platform would not negate the inherent limitations of the Bushmaster in these sorts of operations but it would go some way in mitigating its vulnerabilities.

Once contact was made with the enemy off the line of march, motorised commanders could push their vehicles up to flanking fire support positions.

Provided the Bushmaster or Hawkei crew had crest clearance to the target, the dismounted manoeuvre commander could then call for fires from his mounted call signs.

Fires would then be able to be adjusted on to the target, controlled and cut-off by any soldier qualified as a Mobile Fire Controller, Gun Fire Controller, or Joint Fire Controller.


At present, indirect machine gunnery is a skill maintained by a small minority of the infantry in DFSW Platoons. In theory, there is no reason why these skills could not be mimicked by a relatively simple robotic weapon platform. This platform could be mounted to any Bushmaster and Hawkei in the Australian Army.

For relatively little investment, Army could provide motorised commanders with the ability to call upon an organic fire support platform whilst conducting dismounted clearances. This would provide motorised infantry commanders with greater tactical flexibility when not being supported by armoured, mortar, DFSW, or artillery callsigns, significantly improving their ability to fix and manoeuvre against the enemy.

Indirect machine gunnery guards against the Bushmaster and Hawkei’s inherent vulnerability against direct fire and anti-armour weapons and, if employed cunningly and intelligently, enhances the lethality of motorised combat teams and battle groups on the battlefield.



Chris Thorburn


Chris Thorburn is an Army officer, posted to Headquarters Joint Operations Command.


The views expressed in this article are those of the author and do not necessarily reflect the position of the Australian Army, the Department of Defence or the Australian Government.


Congratulations Chris.  A great proposal, well presented.  I hope it achieves the influence it deserves and encourages others to contribute their ideas as you have done.  I just have a couple of points to offer. Firstly, the beaten zone of machine gun fire would suggest that the location of the firing point vis a via the target, is critical in terms of the effectiveness of the fire.  An extension of the capability you propose would be its incorporation into planning for, say, support for a deliberate attack; or suppressive fire to restrict the enemy's freedom of movement. Secondly, you state that "Vehicles will never be able to achieve surprise in the same way that dismounted DFSW soldiers can".  I know what you mean (ie. Bushmaster, Hawkei vehicles), but there is a more generic view.  Vehicles will always have the potential to achieve surprise, by virtue of their mobility.  The advantage to be gained, depends on the nature and number of the vehicles.  With the Bushmaster, the advantage might be in the unexpected deployment of combat troops to a particular location.  With the Hawkei, it could be the demolition and blocking of a critical defile. As an aside, I wonder if extended range ammunition is available, ie. with a longer tracer burn out time.  It would be nice to think that the firepower that could be brought to bear, could also be adjusted (but I guess this might be a bridge too far).  Finally, would the weapon mount on the vehicle have to be 'stiffened'?  Best wishes

Hi Chris, time to dig in to the archives in support of your idea. The technology of what you seek is very much possible, probably not more than a software upgrade to your RWS. But the beauty, the art in delivering the effect, including choice of weapon/ammunition combination is in the Support Weapons School's archive.  The techniques and tactics for orchestrating Medium/Heavy MG effects at ranges out to 5600 yards were the bread and butter of the MG Battalions officers. The Vickers gun, water cooled and firing long rang .303 was able to suppress, deny and channel. It was replaced by the L7 in the rush to airportability and in support of the move to 7.62mm. But in the role you are proposing, weight is not an issue; and ammunition in sufficient quantity to achieve the effect can be carried.  Worth a look, anyway, Chris.

Interesting but doesn't add to combat firepower.Why wouldn't we just have more mortars? Greater range bigger danger area. Time to take the leap and acquire 120mm mortars for the battalion mortar role and move mounted 81mm mortars to company level.

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