patrick.net

The mission of that night's operation remains unclear, but the forces were advancing towards a valuable oil and gas field, Coneco, controlled by the Syrian Democratic Forces (SDF), a US-backed militia that has been fighting ISIS in Syria.

When the pro-regime forces began shelling a base held by the SDF, the US responded with heavy airstrikes and artillery fire, which continued for about three hours.

The results were devastating. The accounts of several of the Wagner contingent, as relayed to friends and family, speak of carnage as US commanders deployed AC-130 attack aircraft, helicopters and artillery in response to the attack.

Valery Shebayev, who visited some of the injured in a Moscow hospital, told CNN the group had been ordered to take what was described as a vacant oil field. But they had no air support. Shebayev, who belongs to a Cossack group from which Wagner draws some of its recruits, described what followed as "a massacre."

https://www.cnn.com/2018/02/18/middleeast/us-airstrike-killed-dozens-of-russians-in-syria-intl/index.html
The Lockheed AC-130 gunship is a heavily armed, long-endurance ground-attack variant of the C-130 Hercules transport fixed-wing aircraft. It carries a wide array of anti-ground oriented weapons that are integrated with sophisticated sensors, navigation, and fire-control systems. Unlike other military fixed-wing aircraft, the AC-130 relies on visual targeting. Because its large profile and low operating altitudes (around 7,000 ft) make it an easy target, it usually flies close air support missions at night.[5]

The AC-130 has an unpressurized cabin, with the weaponry mounted to fire from the port side of the fuselage. During an attack, the gunship performs a pylon turn, flying in a large circle around the target, therefore being able to fire at it for far longer than in a conventional strafing attack. The AC-130H Spectre was armed with two 20 mm M61 Vulcan cannons, one Bofors 40 mm cannon, and one 105 mm M102 howitzer; after 1994, the 20 mm cannons were removed. The upgraded AC-130U Spooky has a single 25 mm GAU-12 Equalizer cannon in place of the Spectre's two 20 mm cannons, an improved fire control system, and increased ammunition capacity.

The new AC-130J is based on the MC-130J Commando II special operations tanker as of 2012. The AC-130W is armed with one 30 mm Bushmaster cannon, AGM-176 Griffin missiles, and GBU-39 Small Diameter Bombs (SDBs).[10]

https://en.wikipedia.org/wiki/Lockheed_AC-130
The Mk44 Bushmaster II is a 30 mm chain gun manufactured by Alliant Techsystems. It is a derivative of the 25 mm M242 Bushmaster, and uses 70% of the same parts as the M242 while increasing the firepower by as much as 50% with the 20% increase in caliber size. The barrel is chromium-plated for extended life.

The gun uses standard GAU-8 Avenger ammunition that is available in API (Armor-Piercing Incendiary), HEI (High-Explosive Incendiary) and APFSDS-T (Armor-Piercing Fin-Stabilized Discarding Sabot-Tracer) variants.

The gun can be converted to a caliber of 40 mm, which involves changing the barrel and a few key parts, to use the Super 40 cartridge. It can also be converted to use the 30x170 mm RARDEN cartridge.

https://en.wikipedia.org/wiki/Mk44_Bushmaster_II