Did this route in 2014, made a YouTube video for this trip. There's two open campsites on Quadga Lake...the first one to the right on the point is very nice. (The other is across the lake near the hiking trail.) We liked Quadga Lake so much we went back a couple years later..(Hog Creek to Little Isabella takeout). There's bass and pike in Quadqa, an otter family & a beaver that swims by the camp like clockwork every night.
Regarding the "gunshot". I have had this experience several times, last year on the South Kawishiwi and once in Wabakimi on a project trip. Maybe, but I don't think I was hearing an actual gunshot; though it sure sounds like one! Might be some kind thing where a tree goes over in a certain way...(total speculation). I wonder if others have heard "gunshots" randomly in the wilds???