When I first started teaching (university level), trying to come up with what I thought would be acurate grades would keep me awake most nights.
Asking fellow faculty revealed that they too had wrestled with the same problem, they developed a "feel" for what was right, and that they had simply accepted it as a pain point.
I refused to accept that. One semester I told them at the beginning of the semester that they were competing against their classmates. I was not setting upper and lower bounds for grades, their classmates were.
I used the full range of grades (A+ to F), and when I tabbed the grade distribution, the results freaked me out: It was an almost perfect bell curve. I decided to use the method again the following semester. Same results. I did it again the following semester. Same results again. I then permanently adopted the method.
Other results included the, "Why didn't I get an "A" on Project/Paper X" drama during office hours dropping off to nothing;
Student's were much more comfortable knowing they were competing against their classmates, rather than trying to "figure out" their professor;
My Teacher Evaluation scores didn't change across my changing grading methods;
My stress level went _way_ down, and allowed me to better concentrate on creating and delivering content.