There is no clear definitive answer of our weapon arcs of fire.
I run old school models, and always called them pintle mounted, though blocked by the vehicle hull, giving me about 180 degrees on a front one or about 200+ something on the sides. I also have some that are modeled diferently that theoretically have a 360 degree arc. Venoms also have one pintle and one that is...probably hull mounted, so they are probably a 45 and a 180 respectively. New Raiders/Ravagers also have that shield cupola thing, which makes it look like they have less ability to rotate the weapon.
The basic correct answer is - if the weapon is hull mounted, it has a 45 degree arc.
If the weapon looks like it can otherwise swivel/rotate/turn/et al beyond that point, then *that* is the firing arc.
It's very perception and opinion based.