Was the hand held single .50 effective? and more

[Kryten]

I don't think air gunner accuracy was particularly high during ww2, whether it be pivot mount or powered mount, in effect the volume of fire would have been more the issue to the attacking aircraft, the larger the volume the higher the probability of being hit!
I never understood why they did not use a higher percentage of tracer on defensive weapons, if only for the psychological effect against the attacker?

the nose gunners on the 617 squadron lancs attacking the dams used a very high percentage of tracer to keep the gunners heads down and dazzle them?