FWIW, when I started AG brewing I worked on all the variables individually to get my process as efficient and consistent as possible ( calibration, volumes, measurements, pH ,etc.) and could not get above ~ 68% efficiency at best. It was frustrating because I knew my process was sound. The only thing left was my crush. So I had my LHBS double crush my next batch and my efficiency went to right ~ 80% with otherwise the same process. I've gotten my grain double crushed ever since.