The U.S. Army has found that GPS guided shells were more successful than anticipated. So they are reducing orders for these weapons. The 155mm Excalibur shells are used less frequently than expected, largely because other precision munitions often take out targets before Excalibur gets a chance to. The GPS guided MLRS (GMLRS) rocket has been very popular. And the army uses a lot of Hellfire missiles, fired from AH-64 helicopter gunships. In addition to the reduction in Excalibur production, the army has cut the number of GPS guided 120mm shells, which are to enter service within a year.
Another factor that hurt the popularity of Excalibur, and the ATK 120mm guided shell, is cost. Excalibur was supposed to cost about $50,000 each. Eventually. After all the debugging, and after more of the shells were produced. But the cost is still about $200,000 per shell. The 120mm guided shell will also be pricey, but not as much as Excalibur. GMLRS cost about $100,000 each, and have a much longer range, and a bigger bang.
Another edge GMLRS has is the HIMARS rocket launcher. Only costing about $3 million each, these smaller, truck mounted MLRS (HIMARS) rocket launcher systems have become very popular. HIMARS carries only one, six MLRS rocket, container (instead of two in the original MLRS vehicle). But the 12 ton truck can fit into a C-130 transport (unlike the 22 ton tracked MLRS) and is much cheaper to operate. The first HIMARS entered service in 2005, about a year after GPS guided rockets did.
The 680 pound GMLRS (guided multiple launch rocket system) missile is a GPS guided 227mm rocket that entered service six years ago. It was designed to have a range of 70 kilometers and the ability to land within meters of its intended target, at any range. This is possible because it uses GPS (plus a back up inertial guidance system) to find its target. Two years ago, the army tested GMLRS at max range (about 85 kilometers) and found that it worked fine. This enables one HIMARS vehicle to provide support over a frontage of 170 kilometers, or, in places like Afghanistan, where the fighting can be anywhere, an area of over 20,000 square kilometers. This is a huge footprint for a single weapon (an individual HIMARS vehicle), and fundamentally changes the way you deploy artillery in combat. Excalibur has a max range of 37 kilometers, and 120mm mortars about 7.5 kilometers.
The U.S. Army is buying over 800 HIMARS vehicles The U.S. Army is buying 100,000 GMLRS rockets, most of them fitted with a 89 kg (196 pound) high explosive warhead. About half of that is actual explosives. These have been used with great success in Iraq and Afghanistan, where over a thousand have been fired so far. The guided rocket is much more effective than the older, unguided, version, and is replacing it in most cases. No more of the unguided rockets are being purchased by the U.S.. The accuracy of GMLRS means that one rocket does the job that previously required a dozen or more of the unguided ones. That's why HIMARS is so popular. While it only carries six rockets, that's often enough to last for days, even when there's a lot of combat.
The 120mm mortar round has about 2.2 kg (five pounds) of explosives, compared to 6.6 kg (15) pounds in a 155mm shell. The smaller explosive charges limits collateral damage to civilians. But in Afghanistan, its more common to need a large bang (which GMLRS can deliver). Excalibur was more suited to Iraq, but the American troops are leaving there, and most of the action is in Afghanistan. Moreover, there are a lot of precision weapons readily available to the infantry, that have small warheads. The Javelin missile has a 4 kg (nine pound) warhead, and the larger TOW has a 5.9 kg (13 pound one.) The Hellfire missile has a 9 kg/20 pound warhead. The air force also has its SDB (114 kg/250 pound small diameter bomb, carrying 23 kg/51 pounds of explosives.).
Meanwhile, there is still demand for unguided 155mm and 120mm shells. There are times when you need firepower over a large area (several hundred meters by several hundred meters), and for this, unguided shells do the job best, and cheapest.