All you ever wanted to know about the WWII gun debate right here ....
http://users.skynet.be/Emmanuel.Gust...n/fgun-in.html
More here ...
http://www.quarry.nildram.co.uk/CannonMGs.htm
Note that unreliability in wing mounts was not the only issue. The following factors are also relevant:
- everything else in the US armed forces from HMG in rifleman squads through jeeps and tanks to light AAA mounts on boats used 0.50 cal. From a logistics point of view 0.50 cal was easier to supply.
- even if 20mm was "better" ... if 0.50 cal was doing the job it was uneconomic just to change weapons at random mid war
- multiple 0.50 cal in an aircraft could use a variety of gun harmonization some of which favored less accurate marksman. See the link and diagram below ...
http://www.researcheratlarge.com/Air...nBoresighting/
