MK 4 gun pod (with MK 11 cannon, always two-barrelled) was used by USN fighters only during one line period on Yankee Station for a test.. it was judged " worthless " ... too many problems, like unreliability, pod takes away the centerline fueltank which made it neccessary to use wingtanks which lead to spotting probs on the deck 'cause mounted wintanks are big and "stick out" thus taking much more space etc ...
The MK 4 gun pod was used more frequently by land-based USMC squadrons on F-4 and A-4, which was going OK apparently, since there were no carrier-ops related troubles, but some reliability issues remained.
Another user were the Black Ponies, flying OV-10A . They used the MK 4 pod fromthe centerline station, also reported reliability issues but the pod was great ....if it worked
The three-barrelled pod, thats the GPU-2, with a M-197 20mm cannon, 300 rounds capacity and its battery powered. IOC was in the early 70's, iirc. ( 1972/73 or so)
The SUU-16/23 pods with M-61 Vullcan cannon used all linkless feeds, and only the empty shell casing were ejected . During loading ( with linked ammo), the belt was run through a delinker which stripped the rounds off the links, moving them into the ammo drum
The pods in the video are all SUU-16's