Come on bro. A quarter of a million rounds for just one kill. Say that out loud. That alone should not pass the smell test, is all I'm saying. And to your point there is no real evidence that that ratio is true or even the kernel of the statement is true.
It is estimated the US killed a million iraqis. Are you suggesting the US made, issued and expended a quarter of a billion rounds during Iraq alone?
And the "training" number "omitted." No. Absolutely not. Training, and qualifying range days, the ammunition is highly watched and accounted for. Each company is given a predetermined number of rounds. If the rounds are not used they are counted, recorded and put back into circulation. Each round is carefully accounted for to prevent "accidents, which is a big concern within the military.
No one wants to explain to Susy Creamcheese that her little Johnny was self or other deleted because he was hated or insufferable.