Not good for Handel I suspect if the race really is a toss up (downgraded from Lean R IMO). I suppose Handel is still Lean R because of the lack of flexibility in her district, but June 2017 will be far different than November 2018.
Handel is going to win. Abrams winning will not be enough to carry a one issue political novice across the finish line in an educated district like GA-06. I can imagine many Abrams-Handel voters.
I think you're underestimating McBath. People hear "gun control candidate" and act like McBath is some doomed paper candidate, and while gun control is the reason she got into politics and that's a lot of her personal story, she's more dynamic than she gets credit for. Not to mention GA-06 isn't a bad district in which to run on gun control. Handel is the favorite but McBath certainly has an opening if you ask me.