Not only Excalibur: the history of precision-guided munitions for 155 mm guns from the M712 Copperhead to the M1156 PGK and what they can give the Armed Forces

Lately (even before widespread discussions of the MLRS M270 and M142 HIMARS) MLRS M270 and M142 HIMARS have featured in conversations about military assistance

guns, self-propelled guns and howitzers caliber155 mm. Ukraine already uses M777 “three ax” howitzers and self-propelled guns - Norwegian M109A3, American M109 and French Caesar. Polish AHS Krab and Dana with Zuzana 2 from Slovakia are coming. All this will increase the firepower of the Ukrainian Armed Forces not only due to 155 mm NATO ammunition, which will be supplied uninterruptedly and in the required quantities thanks to the opening of the Ramstein supermarket for Ukraine. But also due to high-precision GPS-guided ammunition, which has another important parameter in war - significantly lower consumption. What gives an advantage in logistics is that fewer of them are needed and the required quantity can be delivered faster (and, ultimately, cheaper). Everyone has heard about the high-precision (and not cheap) M982 Excalibur projectile, but now there are no less interesting ammunition that can enhance the firepower of the Ukrainian Armed Forces.

The advent of artillery guided projectiles (CLGP)

It all started in the USA in the 70s of the last century,when the development of artillery almost hit the ceiling. After the creation of nuclear artillery (there was such a thing in the history of weapons, but it was officially abandoned at the end of the twentieth century), it was necessary to move on somewhere. And a natural development was the attempt to create guided high-precision projectiles. There is a theory that the reason for their creation was the appearance in Eastern Europe (we are talking about the Cold War times) of a huge number of USSR tanks, which by their existence created a serious threat. Therefore, an accurate weapon was required, capable of hitting a tank at a considerable distance, relatively speaking, with one shot. The thing is that in densely populated Europe, firing howitzers into squares (to cover a tank armada) was, to put it mildly, inhumane and fraught with large casualties among the civilian population.

In addition to tanks and other armored vehiclesthe targets of such precision-guided munitions could be stationary fortifications. After a preliminary review of projects, in which almost all weapons manufacturers in the United States took part, a project calledCLGP(Cannon-Launched Guided Projectile - literally"guided artillery projectile"). It was based on the use of a gliding projectile with fins (the version with a solid-fuel jet engine was abandoned in favor of low-cost production) with the same simple and noise-proof guidance system using a laser designator (this technology was new and promising at that time, it was developed by Texas Instruments) in the final stage of the projectile's flight. For laser illumination of the target, one could use a ground operator (GLLD installation made by Hughes Aircraft in the photo below) or an airplane or UAV - they already existed then. The flip side of making the project cheaper was a reduction in the projectile’s flight range.

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Photo:Ground laser target illumination station GLLD (Ground Laser Locator Designator) during testing, 1974 (Wikipedia)

After firing such a guided projectilethe tail stabilizers open, and it continues to fly, receiving the reflected laser target designation signal as it approaches the target. This signal is received by the semi-active homing head and the electronics give instructions to taxi the tail unit during the final seconds of flight. In theory, all this today may not look very convincing, but, according to the results of comparative tests of competing models conducted in 1975, the best of them demonstrated seven direct hits per eleven shots on targets (both standing and moving) located at a distance from 4 to 7 km.

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Photo:prototype of a 155-mm GLLD projectile next to an M109A1 howitzer at the Fort Sill military base (Wikipedia)

M712 Copperhead: the first precision projectile

As a result of the CLGP project, the first155 mm caliber guided artillery shell. It was named M712 Copperhead (literally, copper head, which is also the English name for the copperhead viper). Work on the CLGP showed that the tail unit was not sufficient to fire with the required accuracy. Therefore, wings were added to it, giving the projectile a resemblance to a cruise missile. Serial production of the M712 Copperhead began in 1978 - the Pentagon purchased 3,000 of these shells for $56 million. Another 27 million was spent on 130 GLLD laser target illumination stations. At different times, the cost of one M712 Copperhead ranged from 22 to 24 thousand dollars apiece (this amount did not include the warhead and transportation containers; they were purchased separately). A total of 15,745 rounds were produced from 1981 to 1985, representing 35% of the Pentagon's artillery shell budget. The Martin Orlando plant, when operating in peacetime mode (that is, in 1 work shift), produced up to 700 shells per month. In total, about 25,000 were produced until 1989, when the M712 Copperhead was discontinued.

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Photo:M712 Copperhead shell at White Sands Missile Range Museum (photo by Kelly Michals)

In the diagram below you can see the M712 deviceCopperhead in longitudinal section. From left to right: pan, tail stabilizers, steering compartment (rods and control surface servos), empennage (wings), combat compartment with a warhead weighing 6.7 kg, control compartment, semi-active homing head. The length of the projectile is 140 cm with a total mass of 62.4 kg. The stated firing range of this ammunition is from 3 to 16 km.

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Illustration:The device of the M712 Copperhead projectile in longitudinal section (Wikipedia)

The ammunition has two operating options:ballistic and gliding mode. Ballistic mode is used in high clouds and good visibility. In this case, the aircraft extends its wings and stabilizers at a distance of 3000 meters from the target. Gliding mode is used in poor visibility conditions (clouds, fog or precipitation), which does not allow the use of ballistic mode. At a given point in the trajectory, the ammunition extends its fins and transitions from the ballistic phase to the gliding phase. The target is acquired when the projectile is close enough to detect the laser beam, or when the projectile emerges from the cloud cover, whichever event occurs first.

For the first time, the M712 Copperhead was used in combat.conditions during Operation Desert Storm in 1991 in Iraq. Then 90 shells were fired at radar stations and fortifications of Iraqi troops. Of these, only 4 ammunition did not hit a stationary target illuminated by a laser beam.

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The approach of a projectile to an M47 target tank with subsequent detonation when it hits the target (animation based on a photo from Wikipedia)

To accurately hit the homing headthe target must be illuminated for at least 13 seconds. Before launch, the artillery crew had to program the projectile to receive the corresponding laser beam code (pay attention to the first seconds of the video below - the artilleryman turns special screws with coded markings with a screwdriver), which created additional noise immunity from the enemy.

In 1988, the M712 variant was adopted“Copperhead-2” with a combined (infrared and laser) homing head, which reflected the emergence in those years of the “fire and forget” principle in new types of weapons.

For those who want to know more

  • The Soviet Union developed its own guided missile -Krasnopol. It has been developed since the late 70scentury, used a semi-active laser homing system, had a warhead weighing 6.4 kg (in new versions up to 9 kg, range from 3 to 20 km (in new versions up to 25 km).
  • The modern version of this munition is called Krasnopol-D, uses satellite navigation and is used in the current war with Ukraine.
  • The export version of Krasnopol is estimated at $35,000
  • Lesser-known versions of guided projectiles being developed in Russia areCentimeterAndWhaler
  • Ukraine has developed its own analogue of a guided missile based on the Soviet Krasnopol called "Kvitnik"(9 kg warhead, firing range up to 20km, caliber 152/155 mm). It was put into service in 2012, and in 2017 a version without Russian components was created. In 2009 prices, one such shell was estimated at 200,000 hryvnia.
  • ADC(Artillerie Dirigee Charge) is a high-precision projectile developed in France, with a range of up to 25 km
  • BOSS(Bofors Optimized Smart Shell), developed in Sweden, is a high-precision high-explosive projectile with an armor penetration of 600 mm and a radar guidance system, firing at 24 km

In addition to homing(adjustable) monoblock shells, there is also a whole class of cluster shells with self-aiming combat elements that are inserted into the casings of artillery shells. As a rule, such ammunition is simpler to manufacture (they do not require a control system) and is approximately 3-5 times cheaper than self-guided ammunition. And they are used to destroy armored targets. Since they all fall almost vertically on the target, their ability to penetrate armor of 100-120 mm is quite enough for them to defeat. Their design is based on only two functional units: a target sensor and a warhead. Homing combat elements demonstrate better effectiveness when hitting a moving group target. They are capable of independently finding targets over a significantly larger area. To understand how this works, in principle, it is enough to watch a video demonstrating the BONUS ammunition with two destructive elements (jointly developed by Sweden and France).

During the initial phase of the flight, the projectile movesalong a ballistic trajectory. It then fires two warheads, each of which is first stabilized in flight by two curved fins and then individually aimed at the target. This class of 155 mm caliber projectiles also includes ammunitionXM-898(SADARM, Skeet) made in the USA,ACED(France),Clasp(Israel) andSM Art(Germany).

M982 Excalibur: a projectile for the price of a rocket

The pinnacle of development of artillery shells (andThe holy grail of the fire-and-forget class is the M982 Excalibur guided munition, developed by Raytheon Missile Systems and BAE Systems Bofors. Initially, it had a combined guidance system (inertial + GPS, in modern versions a laser homing head appeared), providing it with outstanding accuracy with a circular probable deviation (CEP) of 4 meters at ranges up to 40 (in some later modifications up to 57 km ). For comparison, standard American 155-mm shells have a COE of about 200-300 meters when fired at medium range. Weighing 48 kg, it has a 22 kg warhead and costs about $112,000 apiece, which makes Excalibur, to put it mildly, an expensive pleasure, designed to hit selected targets (command posts, electronic warfare/reconnaissance systems, and so on). An important advantage of high accuracy is the ability to use such a projectile in close proximity to one’s own infantry without the risk of damaging it with “friendly fire.” That is, with the help of Excalibur you can shoot at positions located at a distance of 50 meters from your soldiers, which is simply unheard of by the standards of artillerymen.

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Official Raytheon video demonstrating field testing of the projectile:

Development of Excalibur began back in 1992.The first technical specifications from the US Army (heavily revised over time) appeared only in 1997. After much ordeal (at first the development was common to both the projectile and the guided bomb, then they were separated), in 2005 Raytheon received the first order worth $22 million for a pilot batch of 165 projectiles. Testing was completed in 2007 and that same year, Excalibur was used for the first time in the Iraq War. In 2008, it was already used in Afghanistan (at that time the price of one shell was about $80,000).

One of the disadvantages of Excalibur is shootingagainst stationary targets (GPS coordinates are recorded before firing, this requires special equipment, for example, it is often noted that the American M777 howitzers delivered to Ukraine do not have it, and in general only the A2 versions of this howitzer support such shooting). Between us, all this does not mean at all that this equipment (as well as the Excalibur shells themselves) will not appear in the Ukrainian Armed Forces over time, but now we are not talking about that, but about the fact that a new version of the projectile with the nameExcalibur Scapable of hitting moving targets.In February 2020, Raytheon announced the successful testing of Excalibur S against a moving target using a laser homing head. Its development has been ongoing since June 2013.

For those who want to know more

  • First version of Excalibur with indexXM982appeared in service with the US Army in 2007, it was put into service in a hurry, so they deliberately went for a reduced flight range
  • The production of the first version of the M982 was completed back in 2014, about 6500 shells were made.
  • Since 2014, a version of the projectile has been producedExcalibur М982А1with a CEP of less than 2 (!) meters.
  • Ammunition Excalibur are in service with the armies of the United States, Canada, India, Australia, Jordan and Sweden
  • In February 2012, a Marine Corps M777 howitzerUS infantry in Afghanistan (Helmand Province), fired a single Excalibur projectile, which destroyed a group of Taliban at a record range for the Marine Corps of 36 kilometers
  • April 23, 2022 CBC Canadareported that, along with four relatively new M777 howitzers, Canada also transferred to Ukraine several M982 Excalibur shells left over from the war in Afghanistan.

M1156 PGK (Precision Guidance Kit): a fuze that turns a 155mm projectile into a highly accurate one

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Photo:USAASC (U.S. Army Acquisition Support Center - US Army Procurement Support Center, 2018)

Everyone enjoys the problem-solving Excaliburaccuracy of artillery shells, if not for its cosmic price. And although it has already been halved compared to the initial versions of this high-precision projectile, its cost is too high. What if it was possible to develop some kind of kit that would turn any projectile into a high-precision one? This is the question the US military asked itself when it organized and financed the programs.CCF(Course Correcting Fuze - course correcting fuse) andGIF(Guidance Integrated Fuze - fuse with integrated guidance). Both of them resulted in the creation of the projectPGK(Precision Guidance Kit - a set of high-precisionguidance). In theory, his work should have looked like the video below, and the advantages (besides the obvious accuracy) were still the same: reducing the cost of production and logistics of ammunition by 3-4 times:

First PGK prototype with indexXM1156created by the same Raytheon, which produces Excalibur,but in the end, BAE Systems won the supply contract. Although the development was completed by a third company - Alliant Techsystems Inc. (ATK). It is now defunct following its acquisition by Northrop Grumman Corporation in 2018. As a result, the army received a fuse compatible with any 155-mm projectile, the CEP of which (like the Excalibur) did not change depending on the range of the shot. In the first version of PGK, the circular probable deviation was 50 meters, but after several iterations of development, it was reduced to 10 meters. At the same time, the PGK fuse had an interesting feature - 5 seconds after the shot, the electronics calculated how much the arrival point differed from the GPS coordinates specified before the shot, and if it exceeded 150 meters, the fuse was blocked and the projectile did not explode. This made the use of PGK shells safe for their own infantry. Although in new versions of the PGK software an option has appeared that allows you to disable this blocking - in this case the shell would explode in any case (after all, shooting is not always carried out in close proximity to the positions of friendly infantry).

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Illustration:Comparison of COE when firing a standard 155 mm projectile (with meteorological data no later than 30 minutes), a PGK projectile and an Excalibur projectile (

So, the XM1156 represents a significanta cheaper alternative to Excalibur (the kit costs about $10,000, which is about 10 times cheaper than a high-precision projectile). Moreover, it is compatible with millions of 155-mm shells already produced. Inside the PGK is a GPS receiver and an alternator (the system does not require power; the power is generated in flight). It weighs 1.4 kg, which is 0.45 kg more than a standard fuze (mainly due to the addition of stabilizer fins and an alternator). The fuses themselves are of two types: contact and with remote detonation to increase the destruction of the enemy from an explosion in the air. During the flight, the ammunition corrects its direction by rotating the stabilizer blades around its axis, taxiing to the GPS coordinates recorded before the shot.

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Ultimately, the purpose of creating PGK wasconvert standard rounds into precision rounds and upgrade the millions of rounds already in stock. And all new smart projectiles like Excalibur should only be used for stockpiling.

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Photo:Alliant Techsystems, 2014

This is what it looks like to use the M1156 PGK liveduring exercises. Before firing, the gunners remove the protective cap, pre-programming the target coordinates. And check the performance of the stabilizers (do they rotate easily).

In July 2020, BAE Systems receivedA 33-million contract for the development by 2023 of an upgraded version of the LR-PGK (Long Range Precision Guidance Kit) for 155-mm projectiles with a range increased to 70 km. In addition to the flight range, they promise to improve the noise immunity of the GPS receiver (apparently for the operating conditions of enemy electronic warfare systems) and further reduce the CEP (in essence, to increase accuracy).

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For those who want to know more

  • In October 2012, Fort Bliss soldiers used an early XM1156 PGK prototype for the first time in a training exercise, firing 24 rounds
  • In September 2014, the PGK was tested with German DM111 shells fired from a PzH2000 self-propelled howitzer from a distance of 27 km. 90% of projectiles equipped with PGK hit targets within 5 meters
  • Since 2015, PGKs have been supplied to the armed forces of Australia and Canada, and since 2018 - to the Netherlands
  • By 2017, the number of PGKs produced exceeded 10,000 pieces
  • To program GPS coordinates, usespecial device - EPIAFS (Enhanced Portable Inductive Artillery Fuze Setter - Enhanced Portable Inductive Artillery Fuze Setter) M1155
  • Own, "Russian version" PGK with a moduleGLONASS navigation for 152-mm projectiles was developed by the Moscow Design Bureau Compass back in 2011. Fortunately, this design bureau has been disbanded for almost 5 years now.

In the dry residue

Despite the fact that high-precision artilleryshells have been around for many, many years, they are already in service with both Ukraine and Russia (albeit in small quantities, and there is no talk of serial production of the Kvitnik at all), only the M982 Excalibur and the prospects for its supply to Ukraine. Depending on the binary point of view (“zrada” or “peremoga”), the idea is promoted whether they will or will not be supplied. Life, as always, turns out to be much more complex, varied and confusing. And it does not give simple answers to complex, complex questions. What is worth knowing about all this? Firstly, all types of precision-guided ammunition are constantly being improved - the process is ongoing and right now. Secondly, Excalibur itself is constantly improving, as is its more mainstream alternative in the form of PGK. Third, this war represents a unique opportunity for all weapons developers to test them in real combat conditions. Therefore, the question of whether high-precision projectiles will be supplied to Ukraine or not, in principle, is not worthwhile. It is only a matter of time, the report of which has already begun, with the first deliveries of 155-mm artillery of all types, launching the process of rearmament of the Armed Forces of Ukraine to generally accepted NATO standards. And now the first place in priority is not the supply of high-precision ammunition, but the saturation of the Ukrainian Armed Forces with barrel artillery (let’s also not forget about modern MLRS of NATO countries), the needs of which are already estimated in hundreds of pieces. And the main limiting factor today is not the lack of political will for their supply, but the capacity of training centers (the more complex modern equipment, the longer it takes to train - for F16, for example, unlike M777 howitzers, it no longer takes days, but months, plus building infrastructure, which takes years). Therefore, we stop panicking and, in especially serious cases, send alarmists a link to this text. Everything will be Ukraine.