IIRC; the SCP did add in a check to stop this, but I think it was a bit buggy and/or resource intensive. It may still be in the code; I'm not sure. Either way it's a known issue with FS2 1.2.
Any reasonably postioned turret with a sensibe fov shouldn't do this (i.e. on a flat surface, no obstructions, fov 180 at the very extreme maximum)...I'm not sure on secondaries; I think fov applies to firing, but the missile code after being fired allows for that problem.
Anyways, there is a fix done, I'm not sure if it's formally part of the SCP codebase. Probably not, if you have the problem and aren't using (I assume) retail.