Unwell Raptor -
ISTT that most P-47s had eight .5 inch (although two guns were sometimes removed to save weight).
B-25 had up to 12 forward-firing (eight in solid nose plus four in packs on the side of the fuselage) in addition to the mid-upper, although some of the aircraft had only two pack guns and some had none at all. The nose could be retrofitted to earlier models, and I gather (but have seen no evidence to support) that some B-25Ds were so modified.
As well as the dirt problem with cannon, they were initially mounted on their sides. Oddly enough, this led to jams.... The eventual solution was to mount them the right way up and compromise the elegance of the Spit's wing by putting bulges on upper and lower wing surfaces.