Converting Heavy Scout Aircraft to XM21 Minigun System
In 1967 the UH-1C Heavy Scout gunships had two M-60 flex machine guns on each side.
This conversion replaced them with a minigun on each side. see History Miniguns. bap Oct 2021
This is how the flex guns of the XM16 Armament System looked on the Heavy Scout aircraft. See Reggie Slater Video to see them in action. The PIC (left seat) used a flexible sight to direct and fire the weapons.
The new XM21 Minigun Armament Subsystem was mounted on the XM-156 Multiarmament Mount that was used on all aircraft with the seven or nineteen shot rocket pods, and was part of both the XM-16 (quad M-60CA1 7.62mm machine guns) and the XM-21 (twin minigun) subsystems. Included with the XM-156 was the XM-60 Reflex Sight used by the pilot to fire the rockets. The XM-60 was mounted on the windshield frame above the right seat. It could be stowed by pivoting to the left.
Each turret of the XM-21 subsystem carried a single M-134 7.62mm Minigun, which was fed ammo by a single flexible chute that led from the ammo box mounted against the aft bulkhead in the cabin and passed through holes in the floor of the cabin and fuselage in order to clear the sliding door. Each minigun was supplied by two rows of ammo boxes (six total) via a continuous belt of linked ammo. The belt routed from one row of boxes to the other via a cross-over chute and ammo drive motor assembly that attached to the end of the boxes. The right XM-21 minigun draws its ammo from the aft two rows of interconnected ammo boxes (see photo below) in the ammo system. Note the crossover feed assembly and cartridge drive motor attached to the rear box rows. Each gun was driven by the attached electric motor that spun the six barrels and provided a limited ability to pull ammo from the chute. The miniguns were aimed with a flexible reflex sighting station that, when not stowed, hung down from the roof above the left pilot's seat. This sight controlled the miniguns and depressed and flexed them as needed. This XM-21 with seven-shot pods was the most common weapon setup used on the UH-1C in Vietnam.
Tom Fleming: 23Sep2021: The Miniguns may have been tested before the famous night firing by CPT Eschenwald.
The official arrival of the XM21 mini-gun systems may be listed as April 1967, however, there is a good chance that we had a system earlier for testing purposes.
Bruce Powell: Sep2021 I remember the day that the civilian tech reps were on the flight line installing the mini-gun system on one of our Heavy Scout Ships. We all watched with great interest. I think some of the Crew Chiefs were not excited about sitting next to this monster gun in flight, and tried to move to slicks. CPT Eschenwald was chosen, or volunteered, to do the night test firing. Many of us were standing outside of Operations that night, listening to the communications with Eschenwald. We could see him just outside the southeast perimeter of Cu Chi over the Devils Playground area. He rolled in, fired both guns at 4000 rpm. The sky lit up, the noise was a deafening roar. "Oh these fugging meanie guns!!!" he transmitted in his slight Puerto Rican accent. It was very exciting. We couldn't wait to get the other gunships converted.
Think about this: Every fifth round is a tracer. You are only seeing 1/5th of the rounds fired.