The U.S. Army has two GPS guided artillery shells; Excalibur and the new XM1156 PGK (Projectile Guidance Kit). PGK is actually a large fuze that screws into the front of a 155mm or 105mm shell. This longer fuze contains a GPS and small fins to guide the shell to a precision hit. The original version was much less precise than Excalibur. That is, the first PGKs only ensured that the shell landed within 50 meters (160 feet) of the target. If it did not hit within 150 meters, PGK deactivated and the shell dids not explode. The first version of PGK was subsequentkly tweaked so that by 2012 it landed within 32 meters. The most recent version has been further improved the land the PGK guided shell within 12 meters. This version also fixed reliability problems and now the PGK is 94 percent reliable.

Unfortunately the troops still prefer Excalibur. As a result because of that and overall cuts in the army budget, the number of PGK fuzes to be bought in 2015 has been reduced sharply (from 4,857 to about 2,000). This means the price of a PGK won’t hit its goal of $10,500 and will instead be closer to $15,000 each. Meanwhile Excalibur is down to $70,000 per shell and falling.

Both Excalibur and PGK have revolutionized the use of artillery. An unguided shell will normally land within 267 meters of where it is aimed at maximum howitzer range (18 kilometers). An Excalibur shell lands within 10 meters of the target but PGK is cheaper and turns any unguided shell into a GPS guided one. The army sent the first PGKs to Afghanistan in 2013, after successful testing in the United States. The big question was how important would the troops find the accuracy and reliability differences between Excalibur and PGK. Initially the army bought 2,400 PGKs and the U.S. Marine Corps got 700. There is one export customer. Australia has ordered 4,000 PGKs. The army still plans to buy over 20,000 PGKs, but that will take a lot longer with the increasing budget cuts.

It turned out that the troops preferred the more accurate and reliable Excalibur over PGK but found PGK could do the job, just not as well as Excalibur and often required firing two PGK shells to ensure the target was hit.

To further distinguish Excalibur the manufacturer has developed a dual mode version that all allows for use of a laser designator. This provides even more accuracy, usually putting the shell within a meter or two (less than seven feet) of the aiming point. Excalibur is often called in when precision is the main requirement and this dual mode version provides the greatest accuracy available with any guided munition.

Price is also a consideration. The Excalibur shell bought in 2014 cost $70,000 each, which is down from $150,000 each when Excalibur first entered service in 2007. Ultimately the price is to get down to $50,000, which some say has already been achieved if you don’t count development costs. Meanwhile development work continues. Excalibuur Ia added the laser guidance option as well as increasing range from 25 to 40 kilometers. Because Excalibur uses a lot of Swedish technology the Swedes will continue development if the United States drops out. At the moment that seems unlikely because the higher accuracy versions of Excalibur are preferred by the troops and for many missions the higher accuracy (landing within two meters/7 feet) is essential. There will always be a need for Excalibur, just not as many as originally believed.

The U.S. Army spent billions to develop the highly accurate M982 Excalibur GPS/laser guided 155mm artillery shell. But because so many other weapons have shown up with the same kind of accuracy, Excalibur is not that much in demand. Despite initial enthusiasm for these GPS guided shells Excalibur was less frequently used than anticipated. So orders for these weapons had to be reduced. So far the army has bought or plans (thru 2016) to buy only 6,876 Excalibur shells.

There was less demand for Excalibur shells largely because other precision munitions often take out targets before Excalibur gets a chance to. There’s a growing number of other GPS (or laser) guided weapons available. The GPS guided MLRS (GMLRS) rocket has been especially popular. And the army uses a lot of laser guided Hellfire missiles, fired from AH-64 helicopter gunships or UAVs. In addition to the reduction in Excalibur production, the army cut orders for GPS guided 120mm mortar shells (introduced in 2011) after a year of use.

The army wants to build up its stockpile of Excalibur and PGK, but because Excalibur got into service first and proved more accurate and reliable than the later PGK the army is stocking up on Excalibur first, and then the cheaper (and improving) PGK. Ultimately items like PGK will replace Excalibur, but for now Excalibur is the more mature and effective technology. But if there is a major war, the cheaper and easier to produce PGK will be the more practical choice.