The U.S. Marine Corps has decided to buy only six Harvest Hawk kits instead of nine. Each of these kits can be used to quickly turn one of ten modified KC-130J transports into a gunship. Meanwhile the marines are also upgrading all their Harvest Hawk kits with new or improved software and electronics (mainly for sensors and communications). Such upgrades have been coming regularly since the first Harvest Hawk kit arrived in Afghanistan in 2010. The marines are also upgrading the KC-130Js already modified to use Harvest Hawk. For example in 2012 the first KC-130J got a modified rear door (the Derringer Door) that enables missiles to be fired, and the missile launcher reloaded, without first depressurizing the aircraft and lowering the rear ramp. This solved a major problem because initially you had to lower the rear door to fire missiles and reload the launchers. Since the aircraft usually operated at high altitude (6,400 meters/20,000 feet) the crew had to put on oxygen masks and it took time to depressurize the cargo bay and lower the rear ramp. The new door has ten launch tubes that can be used (for firing or reloading) while the ramp is closed.
The KC-130J is the latest, and largest, marine version of the C-130 transport used for aerial refueling. But the KC-130J can also carry cargo and weapons (bombs and missiles) hung from the wings or fired from inside. This last capability is for the Harvest Hawk version of the KC-130J. This "instant gunship" system enables weapons and sensors to be quickly rolled into a C-130 transport and hooked up. This takes a few hours and turns the C-130 into a gunship (similar in capabilities existing AC-130 gunships). The sensor package consists of day/night vidcams with magnification capability. The weapons currently consist of ten Griffin missile launchers plus four Hellfires and at least four Viper Strike hanging from the wings.
Viper Strike is a 914mm (36 inch) long unpowered glider. The 130mm diameter (with the wings folded) weapon weighs 20 kg (44 pounds). Because the Viper Strike comes straight down, it is better suited for urban warfare. Its warhead weighs only 1.8 kg (four pounds), and less than half of that is explosives. This means less damage to nearby civilians, but still powerful and accurate enough to destroy its target. A laser designator makes the Viper Strike accurate enough to hit an automobile, or a foxhole.
Griffin is a 20.5 kg (45 pounds) glide bomb that has a 5.9 kg (13 pound) warhead. Griffin has a greater range (15 kilometers) than Hellfire because of pop-out wings that allow it to glide after launch. Griffin uses laser, GPS, and inertial guidance. The Hellfire II missile has been around a lot longer, weighs 48.2 kg (106 pounds), carries a 9 kg (20 pound) warhead, and has a range of 8,000 meters.
The big thing with gunships is their sensors, not their weapons. Operating at night the gunships can see what is going on below in great detail. Using onboard weapons gunships can immediately engage targets. But with the appearance of smart bombs (GPS and laser guided), aerial weapons are more available to hit any target that is found. So Harvest Hawk would be able to hit targets that were "time sensitive" (had to be hit before they got away) but could also call on smart bombs or laser guided missiles for targets that weren't going anywhere right away. Most of what Harvest Hawk did in Afghanistan was look for roadside bombs or the guys who plant them. The marines wanted to track the bomb planters back to their base and then take out an entire roadside bomb operation. This worked quite well and Harvest Hawk may be returning to Iraq to use what it learned in Afghanistan.