Don't remember where to look for range, but precision is easy to modify:
Use Notepad to open sim.cfg found in Data\Cfg. Find this entry near the top:
Code:
[AI Cannons]
Max error angle=3 ;[deg]
Max fire range=6000 ;[m]
Max fire wait=12 ;[s]
The lower the max error angle, the more precise the AI.
Max fire range here means at what distance the AI will open fire at you, not the range of the guns per se.
Remember to KEEP A BACKUP OF THE ORIGINAL FILE!!!