I realize in general never is a poor word to choose. But chosen it I have, and as I mentioned I'm adament. Poor choice or not, I believe it fits.
Plus, it only takes a single snapshot with 8x50cal to down any plane. He may have been one of the few able to aim, or may have simply been lucky enough to get in behind 6 planes that were busy on somebody else.
Technically speaking, the P-47 could hold 500 rounds off the assembly line. I've read that a number of places this was the maximum possible load (never used, mind you). Even preliminary testing of the 47C model states that the 300rpg is most likely only to be used with 6 guns, and that in combat 267 for 8 guns would be the limit, possibly less to save weight (200 rpg being suggested a number of times).
You realize that much ammo is nearly 500lbs of extra weight? He wouldn't have been able to stay with his wingmen in climbout, formation, or combat. Would not this fact have earned some attention (i.e. "he fell behind but caught up in time to bag 6 huns")?
As I mentioned, far too many holes and other possible explanations in that story, and no concrete details to fill them in. Can you find any OTHER examples/records/reports? Other than this one doubtful case?
It's a funny thing. For the longest time I (and many others apparently) thought the Me410 could load out 2x 30mm mk108 guns. There was even talk of 4x Mk108s, and a mixed pair of mk108 30mms along with 2 extra 20mms outboard of them. Then, turns out this is all anecdotal and never happened. Seems the 410 never (there's that word again, but it's accurate) carried the mk108 30mm cannon. Moot brought this point up in another thread.
I bring it up here to simply highlight how these urban legends can spread like wildfire, which is how I would describe the lone example of a P-47 with "double ammo belts" (urban legend).