I don't know whether to laugh or cry.
Been watching Charles Durning lately as Tommy's Dad on Rescue Me.
I have personally fired .50 AP at 10mm rolled homogenous armour, and it barely made a dent (0 deg. incidence 100m range.) If anyone claims to have taken out a tank with a machine gun, let me get into my old tank (Leopard 1), they can get into their plane, and we'll duke it out. I'll bet I win! Don't believe all the stuff you see on the net! I would even doubt 20mm hispanos or 30mm mk 108's would do much. Maybe a mk. 103 30mm, but only the AP rounds, not HE. BTW, the guy was in a Firefly: all of their tanks were Fireflies, as their divisional commander, General Worthington, wanted them to have the best available as they were an in-front of the front lines divisional recce regiment.