Fragment of WW2 aerial gunnery target.

[CINDERS]

About all the Defiants were good for no wing mounted forward firing MG's and a death trap of a turret for the gunner, when 109's encountered them they got a nasty surprise and a few 109's coming in for a stern attack were shot down however it did not take the German fighter pilots long to realize there were no forward firing MG's so from they then attacked from dead ahead as the 4 gun turret could not fire through the propeller arc.
The extra weight of the 4 gun turret plus gunner hampered performance markedly so they could not really jink around the sky as much as the standard Hurricane.
They were shot down in droves eventually moved to a night fighter role then phased out as better types came on stream.