The U.S. Navy, having completed successful testing of its new 155mm AGS (Advanced Gun System) in 2013 has now asked defense firms to provide similar GPS guided shells for navy 127mm (5 inch) guns. The navy made it clear that there was no money for more development, but given the number of GPS guided shell systems available out there for 155mm guns (mostly army artillery) and 120mm mortars, someone probably has something for navy 127mm guns that can be bought “off the shelf” and immediately be put to use. This would make naval gun fire against land targets much more effective and get more out of the limited ammunition supply each ship carries. Even the cost of these smart shells (over $50,000 each) does not diminish the advantages.
The 155mm AGS is only used on the new DDG 1000 ("Zumwalt") destroyers and only three of these are being built and each has only two 155mm AGS. It may be decades before the navy can afford to develop and buy a new surface warship that can handle the larger and heavier 155mm gun. Only a few DDG 1000s are being built because costs grew too large for the navy to afford any more. So for the next decade or so all the navy can afford is some upgrades on its 62 Burke class destroyers, each armed with one 127mm gun. Buying GPS guided shells for the existing 127mm guns on these destroyers would be such an affordable upgrade.
The AGS used the LRLAP (Long Range Land Attack Projectile) GPS guided shell, which during tests hit land targets 83 kilometers distant. It was only in 2011 that LRLAP, after six years of development, had its first successful test firing. The AGS was designed to fire GPS guided shells up to 190 kilometers. That GPS guidance system enables the shells to land inside a 50 meter (155 foot) circle at that extreme range. The AGS shells carry 11 kg (24 pounds) of explosives. The AGS uses a water cooled barrel, so that it can fire ten rounds a minute for extended periods. Each AGS on the DDG 1000 carries 335 rounds of ammo, which is loaded and fired automatically. The AGS shell was originally supposed to enter service in 2015. That has now been delayed to 2018.
The AGS round succeeded where an earlier project, that ended in 2005, after twelve years of effort and two billion dollars, to develop a GPS guided round for the 127mm naval gun. This ERGM (extended range guided munition) system never worked reliably and was not any better when used in the larger 155mm AGS. The LRLAP was designed for the unique AGS design and was not transferrable to the older 127mm gun.
So the navy went looking for another solution. Taking note of the success of the 155mm Excalibur, the navy ended up using some of that technology for its AGS. The navy wanted to use AGS on new warship designs, in order to get more effectiveness out of the limited amount of ammo a ship can carry. Accuracy is the key. A "dumb" (unguided) artillery shell will land with 75 meters (or more, depending on range) of the aiming point, while the laser guided Copperhead (an older army 155mm design that was too expensive) would land within a meter or two. GPS guided shells will land within 3-25 meters of the aiming point.
The U.S. Army has a similar 155mm round, the Excalibur, which entered service in 2007. Excalibur has a max range of 50 kilometers and will land within a 20 meter (62 foot) circle. In practice, Excalibur will land within a few meters of where it's aimed. Each Excalibur shell carries 9 kg (20 pounds) of explosives. The AGS shell has a longer range because it is fired from a longer barrel using a more powerful propellant charge. AGS rounds are also capable of the same accuracy as Excalibur, but it depends on the quality of the GPS signal in the area. The Excalibur manufacturer developed a 127mm version and this is the one the navy is willing to test. There are several other similar 127mm designs for naval guns and the navy is willing to look at those as well.
Excalibur has proved very popular with army troops, but with so many other guided weapons available (especially the 227mm GPS guided rocket), not many are used. In Afghanistan 5-10 Excalibur shells were fired a week during peak periods. For this reason, AGS may never be heavily used for supporting troops ashore. Adding a terminal guidance system to the AGS shell would make it suitable to attacking other ships. Some naval officers have urged the adoption of the army 227mm MLRS rocket but there’s too much support for AGS for that to happen, at least not yet. Meanwhile, Italy has put into service a GPS guided 127mm shell (Volcano) that has a 100 kilometer range and works. The Italian 127mm/64 a bit longer than the U.S. 127mm/54 models, but that would not reduce range of the rocket assisted Volcano shell by much. The 64 means the barrel is 64 times the diameter of the gun or 8.2 meters (or 25 feet) long. The 127/54 barrel is 6.8 meters (21 feet). While there is resistance to buying foreign weapons for U.S. ships there have been several exceptions in the past few decades and Volcano could be another one. The AGS is really too big and power hungry to fit on existing American destroyers and cruisers.
The Excalibur technology could be adapted for use on the 127mm gun most American destroyers carry, as could an even cheaper (and less accurate) technology that uses a larger fuze (the device that is screwed into the front of the shell to handle detonation) containing the GPS receiver and some movable fins to guide the shell. That approach is less accurate this Excalibur remains the leading candidate because the manufacturer has developed a version of the shell with laser as well as GPS guidance. The navy guided shell effort has burned up so much cash, and failed so many times, that growing budget cuts mean if they cannot buy something off the shelf the effort to be halted, for now. Or at least until the Chinese reveal they are working on a similar shell for their warships.