Making the M777 more lethal

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Eight years after the 39-calibre M777A2 ultra-lightweight towed howitzer entered service with the ADF, live fire qualification testing is underway with a new suite of 155mm ammunition that will provide the weapon with increased range and lethality.

This follows the $100 million contract announced in March 2018 under the Land 17-Phase1C.2 Future Artillery Ammunition program for the supply of various 155mm projectile types from Rheinmetall’s Assegai family.

The contract also includes a family of common component fuses from Germany’s Junghans Defence and two separate families of modular charge systems from German-South African company Rheinmetall Denel Munition, and Rheinmetall’s Nitrochemie.

The contract marks the first time that Assegai ammunition has been ordered by a user nation for the M777A2, which is also in service with the United States, Canada, India, and Saudi Arabia.

The munitions supplied via Brisbane-based NIOA in support of the two-year qualification program were divided across two shipments, the first in 2018 and the larger of the two in July 2019. Supply chain issues meant that some undisclosed components were excluded and would be delivered separately, Defence said.

The qualification program includes integration into the Raytheon Advanced Field Artillery Tactical Data System (AFATDS) which provides general and fires command and control capabilities to ground forces, from mission planning to execution.

Warstocks are included in the five-year supply contract, but will not be procured until successful qualification is achieved, following which an additional order is also anticipated for training ammunition.

In due course the new ammunition suite will supplant 155mm rounds from Alliant Techsystems and General Dynamics already supplied to the ADF via the US Foreign Military Sales (FMS) channel.

Qualification testing
Assegai live fire qualification testing began in March 2019 at the Port Wakefield Proof and Experimental Establishment north of Adelaide and is scheduled for completion by mid-2021.

The qualification program includes a number of static and dynamic as well as live fire tests to collect data and ensure the munitions meet Australian requirements for storage, transportation and weapons performance.

The live fire component is extensive and broken into a number of undisclosed phases. It will also contribute towards the production of ballistic data for the Assegai family of munitions that will be incorporated into ballistic software used by the US and other nations.

Australia and the US are working collaboratively to establish the necessary software engineering requirements, a Defence spokesperson disclosed.

Since all Assegai projectiles are ballistically-matched, changes to fire control tables are not required when switching between different capabilities, for example between an infrared illumination projectile and a pre-formed fragmentation round producing more than 20,000 fragments not only from the projectile’s casing but also from encapsulated tungsten spheres.

This ballistic stability is enhanced by a five-zone Rheinmetall Insensitive Munition-compliant modular charge system that is qualified for use in all NATO standard 39-calibre and 52-calibre gun configurations.

All 11 Assegai projectile types are supplied with a boat tail assembly that can be replaced in the field with a base bleed unit, adding about 30 per cent to the maximum range. For the M777A2, this would provide a reach of more than 30km.

A range of up to 41km is achieved by two Assegai Velocity Enhanced Artillery Projectile (V-LAP) variants, a number of which are understood to be included in the Port Wakefield qualification testing.

Currently the long-range precision capability of the ADF’s M777A2s is provided by the Raytheon M982 Excalibur guided projectile, achieving ranges of up to 37.5km with a reported Circular Error of Probability (CEP) of less than five metres – but at a cost of around $70,000 per round.

A much cheaper alternative is the M1156 Precision Guidance Kit Course Correcting Fuze (PGK CCF) which screws into the nose of a 155mm projectile and utilises a GPS guidance package and control surfaces to achieve a 50-metre CEP.

In late 2015 Australia began receiving the first of 4002 PGK CCFs it had requested two years earlier to enhance its inventory of M795 155mm rounds. The M795 is the US Army and US Marine Corps’ standard 155mm high explosive projectile for howitzers, holding a 10.8kg bursting charge and achieving a range of up to 22.5 km when fired from the M777A2.

Presumably to cover ongoing requirements prior to Assegai qualification, one month after signature of the Land 17 Phase1C.2 contract, Defence sought US approval to buy 2,504 M795 high explosive, illumination, and white phosphorous rounds along with fuzes and propelling charges at an estimated cost of US$148 million.

First deliveries to the ADF of 35 M777A2s to replace its 155mm M198 medium guns and 105mm L119 Hamel light guns began in mid 2010. Following cancellation of the self-propelled howitzer requirement under Land 17 (recently revived), an additional 19 M777As were ordered in October 2012 with final delivery made in early 2017.

Of the 54 gun fleet, the 1st Regiment Royal Australian Artillery (RAR) in Brisbane; the 4th Regiment RAR in Townsville, and the 8th/12th Regiment RAR in Darwin/Adelaide have each been issued with 12.

A further 10 are located at the School of Artillery at Puckapunyal, and eight are spread among various maintenance, instructional and proofing establishments.

Each regiment deploys three artillery batteries, each consisting of four M777A2s.

Each battery consists of a gun line (the guns, Troops Command Post and supporting elements); a Joint Fires and Effects Coordination Centre (JFECC); and three Joint Fires Teams (JFT).

On exercises and operations, the JFECC and JFTs generally attach to a manoeuvre unit to provide fire support and targeting, whereas the gun line operates as a distinct entity.

Gun lines typically deploy as four-gun groups. However they can also operate as two-gun sections or single guns (‘pistol’ guns) depending on the mission profile required in the operational context.

Managing sustainment
The number of ‘equivalent full charges’ fired from each M777A2 is recorded throughout the life of the weapon. In addition to this, barrel wear measurements are included in technical inspections.

Chroming of barrels, suggested as a means of mitigating residue developed under specific firing conditions and significantly extending barrel life, is currently undergoing engineering review by the US, Defence confirms.

Work beyond routine maintenance that can’t be conducted at unit level is completed by Joint Logistics Units. Certain repairs require the damaged components to be returned to the US due to the requirement for niche equipment and tools.

Most components of the M777A2 are made of titanium alloy, although some structural components are constructed of aluminium and the gun barrel is made of steel. Total weight is 4,535kg, 41 per cent lighter than the M198 medium howitzer it replaced in ADF service.

The M777A2 is towed from its muzzle by a protected Rheinmetall MAN HX77 8x8 heavy tactical truck with a towing hitch modification. The towing vehicle also carries the gun detachment’s stores and first-line ammunition.

Spare ammunition for the battery is carried on a standard HX77 and trailer while the gun detachment is transported in a Bushmaster troop carrier. The gun is air-transportable by the RAAF’s C-17A Globemaster and C-130J Hercules transports, as well as Army’s CH-47F Chinook heavy-lift helicopters.

According to gun designer BAE Systems, the M198 took 15 minutes to come into action, carry out a five round fire mission and then be taken out of action. The M777A2 can complete the same mission in five minutes, given its maximum rate of fire of five rounds per minute and a sustained rate of fire of two rounds per minute.

Nevertheless the M777A2 lacks the propulsion-capable auxiliary power unit found on some other modern towed howitzers and must be manhandled into position. Traverse, elevation and ramming are conducted manually and ignition of propellant is achieved via an M82 percussion primer rather than by a laser ignition system.

Despite the advent of the Excalibur and other extended range projectiles, the push towards 155mm 52 calibre howitzers firing equivalent ammunition could see the 39 calibre M777A2 in danger of being outranged.

Without air support, outranged artillery can be suppressed by longer-range enemy shelling, allowing shorter-range enemy artillery to operate without fear of counterbattery fire.

This article first appeared in the November 2019 edition of ADM.  

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