This is what the F-16 carries:
Designation     M61A1, M61A2
Type                Six-barrel, hydraulically operated 20mm Gatling gun
Contractor     General Dynamics Armament Systems
Rate of Fire      6,000 rounds per minute
Effective Range   Several thousand yards 
OK, so you fire 1 second bursts - that equates to 100 rounds.  You are flying at an assumed 500mph or 700 feet per second, which means your rounds land in a box 700 feet long.  
Now assume a range of 3,000 yards or 9,000 feet;  and say he let off a couple of rounds as he turned away - say at 25 degrees of turn - he could be 4,000 feet off target horizontally, and landing stuff 9,000 feet away.  It's all too easy....