It's one of the challenges that they will be changing soon. It's going from 150 to 5. So I'd suggest you wait if you don't want to grind.
Another case of communities crying that something is too hard to get so they make anyone older than 5 capable of doing it. 30 kills from 200m and 75 total kills would be a better balance.
I agree that they overcorrected on that one, but that's because it was a bad challenge to start with.
The problem with challenges like "Do x amount" is that they aren't really challenges. They are tasks. They just require you to spend a lot of time repeatedly doing the same thing.
A challenge like "Get a 450 meter headshot" is in my opinion a better challenge than get "Get 75 kills at 200+ meters".
