I want my turret, tur_bldg_chaingun_tripod, to only shoot at enemies that are nearby.
I know basically how to do this for an AI, but how can I have this happen to turrets?

Open up the weapon .odf file your turret uses and edit the same properties you normally would for normal AI. Unless it doesn't use a seperate weapon .odf in that case just add the same properties that change the range the AI shoot at from any other weapon .odf file and edit them accordingly.

Thanks, I just did that and it worked.