+1 to all said. When I started AG brewing a long time ago, I was frustrated with my efficiency which seemed to hover a little over 65%. I worked on thermometer and hydrometer calibration, hitting volumes precisely, hitting mash temps closely, etc. Each improvement helped a little, and I got more and more precise with each batch, but efficiency would go up and down inexplicably. I finally started getting my LHBS to double crush all my grain each time, and I consistently hit ~ 80%. That was the last variable. Much better now. Honestly, an efficiency number is nothing to get hung up on. Just isolate each variable, improve it, and get your grain double crushed ( or get a mill) and your efficiency will be what it is. Shoot for consistency - even if you are consistently @ 70%, it's irrelevant on the home level. You can figure each recipe on the consistent efficiency you arrive at.