from (old) file Player Info.txt
1) An AAMG will be unusable if the vehicle is closed down as it is assumed to be external. (Class 4 weapon with warhead less
than 2 is the split). Larger AAA (class 4) are no longer considered to be unusable if pinned.
That settles it. Heavy guns (as opposed to MGs) are either under armor, remote-piloted or full-size AA guns.
OTOH all class 19 weapons are supposed to be under armor, so use these for remote-controlled or under armor AAMGs from warhead size=1.