My advice here is that less is more when it comes to the crush. Do not over crush your grain! All you need to do is crack the husk open. Just give them a good crack. Some will split, some will kind of hang together, but they will all look like grain. If you can not identify malt kernels after you crushed, your mill may be set too tight.
There is a school of thought that a finer crush will give you better efficiency. It may be true that efficiency can be improved a couple points by turning your grain and starch to powder, but I think the negative tradeoffs offset a couple points of potential efficiency. Namely, the more powder in the mash, the more prone you will be to channeling - and worse – a stuck sparge. The cracked husk is the natural filter that clarifies wort during recirculation. It’s job becomes much harder if it looks more like saw dust than a pile of husks. Visualize what water looks like passing through a bucket of pebbles versus passing through a bucket of sand. That is the difference between a fluffy grain bed and a bed full of powder.
I used to get an efficiency of 85-88%, but going slightly against the grain here, I wanted it lower. I opened my B.C. back up to its factory setting (I tightened it down when I received it), and I conduct my sparge at a faster rate than I used to (usually reaching pre-boil volume levels in less than 30 minutes). I got my efficiency down to 75%, and I could not be happier. Tasting the wort, I find it to be richer, with much less offensive “grainy” character. The cost of richer wort at lower efficiency; about a pound or two of 2-row. More importantly, the fluid dynamics through my grain bed are much improved, and the wort clarity during recirculation has never been better. A stuck sparge used to be my biggest brew day stress – it is a thing of the past.
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