buffnut453
Captain
Valid question. My original answer was probably more based on how the weapons system was used rather than what it was originally specified to accomplish. Given the age and evolutionary nature of the Beaufighter design, I suppose the MGs were there to provide longer firing duration - the use of them for aiming was a beneficial side effect for a specific mission (rocket attacks). The other mission specific useful side effect was suppression of crew in anti-shipping sorties - the 303s kept the sailors' heads (craniums not toilets!) down while the cannons did the more serious damage.