Minimum number of shots for a kill?

[buffnut453]

"One of his victories that night was claimed using only four rounds of ammunition."

The problem with this story is that multiple kills were claimed so I don't know how anyone would know how many rounds were expended on one individual kill, unless the weapon used was a particularly slow-firing cannon or all guns jammed/emptied after one round was fired by each. Irrespective, to record this in combat seems pretty far-fetched to me. Then again, far-fetched things do happen in combat so who knows...?