Armed C-130 Considered For Anti-Small Craft Warfare

It is frequently the case that the best military response to surface ships is with aircraft rather than with other ships or submarines. In this case, the Air Force is testing a modified C-130 intratheater transport aircraft for anti-surface warfare against small craft also designed to support ground troops when there is air superiority.

Aircraft put a much smaller proportion of the force in harm's way (about 5% of the total ground and flight crew of each aircraft) than a naval ship does. An aircraft is like a race car on a track without the pit crew out of the fray. Going into battle in a blue sea naval ship is like going into a combat zone in an RV. 

Aircraft can also respond more quickly, limit their time in harm's way (typically, even the slowest aircraft are 7-15 times faster than the most swift naval ship or submarine) and are literally smaller targets. 

Naval ships are extremely vulnerable to mines, submarines, anti-ship missiles (sometimes hypersonic), and attacks from warplanes. Historic mainstays of naval armament like torpedoes and naval guns are impotent at the longest ranges from which aircraft and missile strikes can be launched. Armor on naval ships can be effective against small arms and irregular forces, but aren't effective against most anti-ship missiles which can be delivered by air, from ground bases, from armed drones, from submarines, or from even small missile boats as well as other full fledge warships. Even so called stealth surface warships are ineffective against pretty simply modern surveillance tools like satellites, drones, reconnaissance aircraft, radar and sonar arrays which are used in concert. 

Aircraft are more easily shifted from one theater of battle to another (this can be done in a few days, instead of a few weeks), which means that you are pretty much stuck with your in theater fleet in the early days of a conflict with ships but can rely on your global aircraft resources.

The US military is trialling the use of the Lockheed Martin AC-130W Stinger II gunship in the anti-surface warfare (ASuW) role in the Middle East. 

The Department of Defense (DoD) announced on 15 March that US Navy (USN) Cyclone-class patrol coastal ships (PC) and Boeing P-8A Poseidon maritime multimission aircraft (MMA) assigned to US Naval Forces Central Command (NAVCENT) had conducted "a first-of-its-kind" joint exercise with US Air Force (USAF) AC-130W gunships assigned to Special Operations Command Central (SOCCENT) on 8 and 9 March. 

According to the DoD, the exercises were designed to enhance the capabilities of US forces to respond to surface threats and involved P-8 aircraft performing long-range reconnaissance ahead of PCs selecting simulated surface targets for the AC-130W to engage.  . . . 

The AC-130W Stinger II (formerly known as Dragon Spear) is a gunship-variant of the C-130 Hercules transport aircraft and is flown by the Air Force Special Operations Command (AFSOC). It is armed with a GAU-23 Bushmaster 30 mm cannon, a 105 mm gun, and stand-off precision-guided munitions such as the Boeing GBU-39 Small Diameter Bomb (SDB) and Raytheon's AGM-176A Griffin missile. AFSOC has 12 such aircraft in its inventory, flying alongside C-130-gunship variants such as the AC-130J Ghostrider.

From here. 

The armament is on the heavy side for ground troops, but small for bombers and similar in magnitude to 330 ton patrol ships like the Cyclone. One primary target in mind for this aircraft is Iranian armed small craft in the Persian Gulf which can swarm larger ships that don't have the resources to hit many small targets simultaneously.