How many rounds of ammunition can a spitfire pump out in 5 seconds?

With .303 ammunition the Spit could fire about 750 rounds in 5 seconds. Since there were only 2400 rounds total it didn't take long to use them all.

I do not have the info for cannon armed Spits but those in service at the end of the war carried enough heavy mg and cannon shells to fire for approximately 1.5 mins.