Guess your right about the accuracy, the way its fixed to the aircraft and how much everything flexes impacts grouping. Guess the patterning is actually not that bad, as it makes the chance that one hits with at least one bullet a bit bigger.
I just remember an anecdote about the swedish Viggen and its 30mm cannon. It is said that the pilot has to "viggle" the plane using the rudder to make sure that not all the bullets land in the same place when firing. Not sure if its true or just our Swedish propaganda at work. :-)
No problem with the table, I have tried to figure it out out, but haven't succeded yet. Not that it matters for the intended use.
The trainees I talked about is the (virtual) pilots that have applied for membership in EAF (European Air Force). Not a school but a virtual sqn.
http://www.europeanaf.org S!
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P/O Mikke EAF331