That's between 10-15 seconds for a solid, continuous full-belt, rock and roll, machineguns a-go-go hold the triger down and hose 'em spray. If he chewed the vehicle up enough to stop or slow it, then finished it off with neat 5 or 6 shot bursts, then I'm really impressed. But either way, he got the job done, and he done good.
As a tank gunner, I was taught that 8 rounds of .50 will disable a softskinned vehicle more than 90% of the time, while it takes 12 rounds or so of 7,62 NATO. This presumes the rounds will get the driver, multiple tires, the ignition system or carburation/fuel injection lines- a hit on a radiator isn't quite good enough.
Indeed, the sharp move would have been to give the driver or steering tires a short *anchor* or *parking brake* burst to ensure the vehicle would remain a target for a few seconds, then hose it down good. Or it may well be that he had the opportunity for a single, continuous 100-round burst, which would get a rookie infantry gunner in trouble with the instructors on an MG range, but might have been just the medicine called for in this particular instance.
In any event, Specialist Ross was just the right guy at the right time. Now if they'd give him an afternoon's time of a range familiarization firing with the M67 90mm or 84mm Carl Gustav recoilless rifles, we'd be right in business. And one shot kills are SO much more sporting.
I really hope Spec4 Ross stopped the vehicle with his first dozen or two shots, as I suspect, and then used the rest of his belt to make certain with nice well-controlled bursts. Belted 7,62 MG ammo routinely comes in cans of three hundred, with three 100-round belts to the can, loaded with 1-in-5 tracer.
Appears to have done just fine. Somebody give that troop a beer on archy.
-archy-/-