poprivit, a question for you: You say the wild dogs weren't afraid of guns, when you were on your safaris - but was anybody shooting at the dogs?
My guess is the dogs in the area where you had your guided tours associate the noise of a gunshot with soon-to-be-available carrion leavings after the hunter field dresses the kill and departs. (Kind of like how, in some areas where bears are not hunted, bears associate gunshots with a buffet to come investigate.) Gun shots in such scenarios aren't scary - they mean their will be wildebeest or kudu parts for the taking.
My guess is the dogs would respond differently if they associated gunshots with the smell of wild dog blood, urine, and scat, and the sounds of yelping, whining, and screaming.