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M777

155 mm lightweight towed howitzer

M777 howitzer

The M777, or 'Triple-Seven', is one of the lightest and most compact 155 mm howitzers ever fielded

 
 
Country of origin UK and US
Entered service 2005
Crew 8 men
Armament
Gun bore 155 mm
Barrel length 39 calibers
Projectile weight (M795 HE) 46.7 kg
Maximum range of fire (M795 HE) 22.5 km
Maximum range of fire (RAP-HE) 30 km
Maximum range of fire (M982 Excalibur) 39 km
Maximum rate of fire 4 rpm
Sustained rate of fire 2 rpm
Elevation range - 2.5 to + 72 degrees
Traverse range 46 degrees
Dimensions and weight
Weight 4.2 t
Length (in travelling order) 9.51 m
Length (in combat order) 10.21 m
Mobility
Towing vehicle 6x6 truck
Road towing speed 74 km/h
Cross-country towing speed 24 km/h
Emplacement 3 minutes
Displacement 2-3 minutes

 

   The BAe (British Aerospace) M777 howitzer is the primary towed artillery piece of the US armed forces, and has effectively replaced the preceding M198 howitzer. It is one of the smallest and lightest weapons of its type ever constructed, due to a combination of a titanium alloy construction and a methodical elimination of as much mass as possible. Though presently produced in the US, the M777 is actually a development of a British design.

   The origins of the M777 date back to the early 1980s, as a private venture by Vickers (which later merged with BAe, the current manufacturer) to develop an exceptionally lightweight 155 mm howitzer for the export market. The primary market for this new weapon was the US Army, who has recently fielded the M198 howitzer, but found it wanting; the primary purpose of the M198 had been maximum mobility and air transportability, but at over 7 000 kg, it was still a rather hefty artillery piece. Vickers was convinced that by simplifying the configuration of a 155 mm howitzer and making expansive use of lightweight materials in its construction, they could make a weapon of equal firepower that was just over half the weight of the M198.

   Needless to say, figuring-out how to make a 4-ton 155mm/L39 towed howitzer took some time and effort (most weapons of this type are significantly heavier), and the preliminary design wasn't ready until the spring of 1987. The main issue had been figuring out how to apply titanium alloys to the construction of the new weapon, in place to traditional steel, as titanium's impressive strength is also equaled by an impressive price tag, and a very high level of hardness that makes it notoriously difficult to machine. The design was presented soon after to the US Army, who were intrigued by the possibility of fielding such a weapon, and they authorized the construction of 2 prototypes in September of 1987. As the federal law prohibits the US military from procuring weapons of foreign manufacture, Vickers teamed-up with Textron to build this weapon in the US. There was also a competing design submitted by Royal Ordnance, whose development roughly paralleled the Vickers design.

   Two prototypes were constructed of the Vickers design, now dubbed the LW155 (shorthand for 155 mm Lightweight Howitzer), which were delivered to the Army for testing and evaluation late in 1989. The US Marine Corps had also taken an interest in the LW155 in this timeframe, seeing potential for such a weapon in their operations, where the weight of an artillery system was at a premium. The USMC evaluated the LW155 as well in 1990.

   In the late 1990s there was a formal competition in which the LW155 was pitted directly against the Royal Ordnance design (by this time named the "Light Towed Howitzer"), with the former ultimately being declared the winner. Following this decision, the US Army formally designated the LW155 as the XM777.

   However, despite passing developmental testing with considerable media fanfare, the XM777 quickly ran into trouble during its operational testing. Under conditions more accurate to actual service use, serious problems with metal fatigue, instability while firing, and damage inflicted by recoil quickly became apparent. These problems became apparent by 1998, and continued to plague the XM777 (and later the M777) for many years. Some have never been fully-resolved.

   In 1999, Textron left the XM777 program, leaving BAe without a US subcontractor to produce the weapon for more than a year. By September of 2000, BAe managed to sub-contract several smaller companies to produce the weapon instead, each of which was to produce a different subassembly of the M777. The carriage was to be produced by HydroMill Inc, the stabilizers, spades and stabilizers by Major Tool and Machining Inc, the loading tray by Rock Island Arsenal, the elevation mechanisms by Wegmann, the optical fire control system by Seiler Instruments and Mfg, the traverse track by Rotek Inc, and the titanium alloys needed to build the complete weapon were to be produced by RTI International Metals Inc. Three companies were sub-contracted to produce the XM777's titanium castings.

   Despite numerous ongoing problems and technical issues with the design, the DoD awarded a $135 million contract to BAe to initiate the Low Rate Initial Production (LRIP) phase of the XM777 in 2002, and formally type-classified it as the "M777". The LRIP contract was for 94 howitzers, the first of which was completed in February 2003. Ultimately, despite the federal law, 30% of the M777 (the suspension, running gear, and upper cradle) ended up being produced by BAe's factory in the UK.

   The general appearance of the M777 is quite peculiar compared to most other towed howitzers, making quick recognition fairly easy. The rectangular muzzle brake is conspicuously hollow, with two enormous baffles. The towing eye is mounted on the base of the muzzle brake, and has a spike-like shape. Unusually, the M777 has no trails. The M777's appearance changes noticeably between its traveling configuration and in its firing position.

   In its emplaced configuration, the M777 sits extremely low to the ground, with its stabilizers swung forward and its spades dropped to the ground behind it --- so low, that when the tube is in a level position, it is barely half a meter above the ground. Despite its low-slung proportions, the M777 still easily achieves high gun elevation, as the pivot point of the gun cradle is effectively behind both the saddle and carriage body. It is also possible to depress the tube slightly, though this capability is seldom used. Seen from above, the spades and stabilizers of a fully-emplaced M777 take-on a crucifix shape, which is essential for stabilizing it due to its lack of conventional trails.

   The appearance of the M777 is even stranger in its travelling configuration. Unlike most modern towed howitzers, the M777's gun is not traversed 180 degrees for towing. Instead, the complete weapon is towed from the aforementioned spike-like towing eye on its muzzle brake. In its travelling position is the two aft spades being folded upward and slightly forward, but not actually wrapping around the saddle.

   Most components of the M777 are made of titanium alloy, though some structural components are made of aluminum, and the gun tube is made of steel. An interesting weight-saving measure is that many of the parts in the M777 serve multiple functions, rather than having a separate part for each. For example, the hydraulics in the suspension are also used as a hydraulic jack. A hydraulically-operated loading tray is mounted behind the breech on the right side, but no rammer is included. Standard M777s have an optical sight mounted on the left side, and provisions for an additional sight on the right side if required.

   A crew of 8 is required to operate the M777 normally. It can also be operated by as few as 5 men in an emergency, but with a significantly-reduced rate of fire. Some publications have stated that the ability of the M777 to be fired by only 5 personnel is unprecedented for a 155 mm howitzer, but the preceding M198 could also be operated as such.

   The M777 requires three minutes to emplace, and two to three minutes to displace. The maximum rate of fire for the M777 is 4 rounds per minute for up to 2 minutes; the sustained rate of fire is 2 rounds per minute.

   Indirect fire for the M777A1 and A2 is usually aimed using the digital fire control system. It provides rapid and accurate ballistic computation, navigation, pointing, and self-location capabilities, which allows the M777A1/A2 to perform effective fire missions rapidly, reducing the amount of time it must be emplaced in a given location. The original M777 lacked this fire control system, requiring the crew to use calculators and dials to compute their firing solutions. All M777s have a direct fire capability, and use day and night optical sights to aim the weapon.

   A wide array of ammunition is used in the M777, a few examples of which are described below.

   The primary projectile for the M777 had initially been the M107 HE round, but this munition is gradually being expended in service and replaced by the M795 HE round. This 46.7 kg projectile hold a 10.8 kg bursting charge, which may be TNT or IMX-101, depending on the customer (the US Army uses a TNT filler, while the USMC uses IMX). When fired from the M777 using an M119 or M203 propellant charge, the M795 has a range of up to 22.5 km, and a CEP of 50 m. The improved charge-to-weight ratio and a significantly improved shrapnel and splintering pattern is claimed by the USMC to provide a 30% increase in lethality over the M107 round, though projectiles with high charge/weight ratios also tend to have reduced penetration (an important consideration when engaging armor and hardened structures). The M107 is still used with the M777 as well, but stocks are slowly depleting.

   The M982 Excalibur is one of the most heavily-used projectiles for the M777. This is a GPS-guided HE round, which boasts fin stabilization and near pinpoint accuracy (the CEP is claimed to be only 5 m), giving it a range of up to 40 km when fired from a 155 mm/L39 weapon, and the ability to be safely delivered in much closer proximity to friendly troops than an unguided projectile usually allows for. The programmable guidance system allows the weapon crew to set the Excalibur to land on a specific geographic location, allowing frontline troops calling-in fire missions to designate specific high-priority targets for destruction by single projectiles (for example, a particularly problematic enemy pillbox). In addition to its GPS guidance, the Excalibur also has inertial guidance, which not only allows the projectile to maintain its ballistic arc even against heavy jamming, but also allows some guidance capability when GPS is unusable altogether (though it won't be as accurate). The Excalibur weighs 48 kg and carries a 22 kg PBXN-9 warhead. Various sources differ on the reported unit cost of the Excalibur, with anywhere from $10 000 up through $214 000, but these figures are misleading. A careful examination of the DoD's Selected Acquisition Reports shows that a combined total of $14 691 Billion was spent on the development and production of a planned 7 474 Excaliburs, making the true unit cost $22 284 Million (the DoD's published figure is off by a factor of more than 1000!). This actually makes the Excalibur more expensive than the M777 itself.

   The M549A1 RAP-HE is a rocket-boosted HE round, which can attain a range of 30 km when fired from the M777 if fired using the Zone 8S M203 Propellant Charge. The M549A1 weighs 43.6 kg prior to fuzing, and carries a 6.8 kg bursting charge.

   The M864 DPICM (Dual-Purpose Improved Conventional Munition) is a submunition-dispersing projectile, which on descent breaks-open and scatters large numbers of anti-personnel and anti-material grenades over a wide area; in layman's terms, it is a "cluster munition". The payload consists of 24 M46 and 48 M42 grenades, which both have a shaped charge (i.e., High Explosive Anti-Tank, or "HEAT"), and a secondary fragmentation effect, making the M864 effective against a wide range of targets. The M864 weighs 47 kg, and has an effective range of 30 km, thanks to the addition of a "base burner" rocket booster.

   The M777 also fires smoke, and a very wide range of mine-scattering projectiles as well. The M712 Copperhead laser-guided artillery projectile can also be fired from the M777, though with only 20 000 made and production terminated decades ago, the stockpile is rapidly dwindling. Any NATO-standard 155 mm shells can also be fired from the M777 as well, which hugely expands the variety of ammunition it uses. The M777's operators may thus sometimes use more unusual foreign ammunition during training exercises and combat operations.

   Canada was the first nation to employ the M777 in combat during the Afghan War, in support of Operation Archer in early 2006. The M777 was reportedly quite effective in this campaign, causing a large percentage of the Taliban casualties inflicted by ISAF forces; most of the damage inflicted on the Taliban was reportedly caused by only two guns. The deployment of Canadian M777s continued throughout 2006. The demand for fire support from these weapons was apparently quite substantial, but so was the consumption of ammunition as a result. It was reported in early 2007 that Canadian 155 mm ammunition stocks in that theater were running low, forcing the Canadian Army to fire less rounds in each fire mission, and perform less fire missions overall.

   The first US combat deployments of the M777 to Iraq and Afghanistan were in late 2007, and the first US M777 fire missions took place in January of 2008. While many of the Army's deployed M777s have long-since been withdrawn from Iraq, the US Marines made their first deployment of M777 batteries to that nation in March of 2016. As of mid-2016, M777s continue to fire in anger in support of operations in Iraq and Afghanistan, despite many in the media having dismissed US participation in the conflicts there being essentially over.

   Though the M777 is very light compared to nearly all other 155 mm howitzers, it lacks the propulsion-capable APUs used in many other modern towed howitzers, such as the FH-70 and G-5. The elevation and traversal of the M777 are completely unpowered. So the M777 has to be manhandled into position. There is also no rammer, so several crewman with a long, curved ramrod must physically drive each shell and powder charge into the breech with their own strength.

   The main value of the M777's 4-ton weight was to be easy transportability by vehicles that couldn't handle the M198, but in practice, only heavy-lift helicopters and 6x6 cargo trucks are actually used to transport it in field conditions. Its much-vaunted transportability by HMMWVs and helicopters as small as the UH-60 are seldom attempted. This is probably due to safety regulations, and the gradual increase in the weight of the M777 since its initial field tests. The M777s are typically airlifted by a CH-47 Chinook, a CH-53E Super Stallion, or a V-22 Osprey, all of which are a far cry from the UH-60 Blackhawk.

   Reducing the weight of the weapon also has no effect on the weight or volume of its ammunition, nor the field supply trains required to carry it, which are a much more significant issue than transporting the weapon itself.

   There are many problems with using titanium instead of steel, rooted in the fact that while it is similarly strong, titanium alloys are much less flexible (making them more prone to metal fatigue), and significantly harder (making them immensely expensive to machine). The awkward proportions of the M777 also stem from the ruthless pursuit of weight reduction, and these present serious practical problems of their own. Also this artillery piece is too light for the powerful 155 mm ammunition. The lighter a weapon is that fires a given projectile and propellant charge, the more violent its recoil is. This has resulted in the recoil-absorption mechanisms in the M777 wearing out dangerously fast in combat conditions. It is highly doubtful that these issues with the M777 can be fully-resolved.

   Another major issue with the M777 is that its tube length is dated. The US Army began using 155 mm/L39 howitzers in the 1960s, and by the early 1980s the 155 mm/L39 had been eclipsed in development, production, and proliferation world-wide by 155 mm/L45 howitzers. These, in turn, are being gradually supplanted across the world by 155 mm/L52 howitzers. The danger of having artillery with a much shorter range than that of the enemy has been graphically demonstrated in the South African Border War, the Rhodesian Bush War, the Yom Kippur War, and the Vietnam War. In all of these conflicts, the side whose guns had a shorter reach ended up being devastated, because their artillery was constantly suppressed by longer-range enemy fire, while larger quantities of shorter-range enemy artillery operated without fear of being bombarded. The advent of the Excalibur projectile also doesn't resolve this issue; though it has an impressive range of 39 km, equivalent ammunition fired from 155 mm/L45 and 155 mm/L52 weapons (such as the Krasnopol-M round and the G-5-52 howitzer) still has an almost 2-to-1 or greater range advantage, leaving the US military vulnerable to the same devastation their fire bases experienced in the Vietnam War, when they came under fire by the Soviet M-46 130 mm field gun.

   As of 2016, the only operators of the M777 are Australia, Canada, and the United States. India has also recently placed an order for 145 M777A1s (though its worth noting that India has proven a dangerous market for artillery producers; this sale follows in the wake of the Denel and Bofors scandals, both resulting in the cancellation of major arms deals due to alleged improprieties). The only other nations so far committed to acquiring M777s are Saudi Arabia and Columbia. The UAE has expressed intent to acquire the ordnance of the M777, which with to create a self-propelled version.

   The M777 has sold in large numbers and production continues. Approximately 1 200 pieces already completed. As of the recent deal to sell 145 M777s to India for $750 million, it has a unit cost of $5.17 million. However the M777 has an unusually narrow customer base for an artillery piece on the market for over 20 years, despite also having extremely heavy publicity. This is mainly due to its high price tag. A typical 155 mm howitzer costs about 1/10th as much.

 

Variants

 

   LW155: Prototype for the M777, built in the late 1990s. It has also been referred to by some sources as the "155LW".

   XM777: Further prototypes of the M777, which incorporated additional improvements and fixes during the ongoing development of the M777.

   M776: Ordnance of the M777, without the rest of the weapon system. The tube used in the M776 is the same M284 used in the M109A6 Paladin, with a modified muzzle brake.

   M777: Basic production model, differing little from the LW155. The basic M777 was only the low-rate initial production model, and all except a few display pieces are being back-fitted to 'A1 or 'A2 standard.

   M777A1: Fitted with a digital fire control system instead of the optical sight. This version quickly superseded in development the original M777. While in development it was designated the "M777E1". Test firings were performed in 2004. The full production contract for 495 M777A1 howitzers for both US Army and US Marine Corps was awarded in 2005. It effectively made the M777A1 the definitive production model during that timeframe. The 'A1 models were to be produced from 2006 through 2009. Some were converted from M777s. The Canadian Forces also placed an order for several M777s during this timeframe as well.

   M777A2: Same as the M777A1, but includes software allowing for the use of the Excalibur GPS-guided round. The first firing trials of the M982 Excalibur from the M777 took place in 2003, though the operational test firings of this round from the M777A2 weren't completed until 2007. Excaliburs by that time had already been fielded in Afghanistan.

   M777ER: Short for "M777 Extended Range", this weapon is an experimental M777A2 variant, with a 52-caliber tube. Though the range is hugely increased by the new barrel, the M777ER is 1.8 m longer and 450 kg heavier than the M777A2, which could pose additional mobility, balance, and handling problems. Program status is unknown.

   M777 Tilt Bed Carrier: Early prototype for an M777 howitzer carrier, which would carry the weapon aboard while in transit, and then drop it to the ground during emplacement. Did not enter production.

   M777 Portee: British howitzer. It is an intermediate design between towed and truck-mounted howitzers. It is armed with the ordnance of the M777. Did not enter production due to funding problems.

 

Similar Weapons

 

   Light Towed Howitzer: Competing design made by Royal Ordnance. This weapon had a much more conventional layout, with very long conventional trails, which were also used to tow it. Did not enter production or service.

   2A61 Pat-B: A Russian lightweight towed howitzer developed in the 1990s, the 2A61 is a 152 mm artillery piece weighing only 4 300 kg, making in on of the few equivalents of the M777 in the world in terms of both bore and weight. Also like the M777, it is towed by its muzzle, and has stabilizers instead of trails. Despite a lengthy evaluation and no official rejection, no production orders were placed, though it is still being offered to the Russian armed forces. The M-389 is its 155 mm version for export. Like its parent, the M-389 never attracted any sales.

   AH4 is a Chinese clone of the M777 with a 155 mm/L39 tube. It has a total weight of 4 500 kg. Maximum range is 25-40 km, depending on ammunition type. This artillery system was revealed in 2014.

   SLWH Pegasus: Developed by ST Kinetics in Singapore, the Pegasus is a similar weapon to the M777, with a 155 mm/L39 tube, a titanium and aluminum construction, and a weight of 5 300 kg.

 

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