Originally Posted by TimpanogosSlim
shredded hulls can make the brew tannic.
I think this is not true at all.
I've been overgrinding my grain forever and have not had astringent brews since my first few (oversparging).
In my first year of all grain brewing I tried to maximize my efficiency by sparging many, many times. What I did was lower the gravity significantly and, consequently, increase the pH. The pH increase is what ultimately (I think) caused tannins to be pulled out of the husks.
So, in my experience, the crush has NOTHING to do with astringency. Just don't oversparge. If you batch sparge, don't do more than 2. If you BIAB, no worries. If you fly sparge, watch the pH and keep it under 6 or watch the gravity and keep it over 1.010. Please check these numbers through google as I just invented them.
To answer the OP, milling too fine can indeed cause lautering problems. If you use a braid, you might need to add rice hulls. I have a keggle with a false bottom that I've fiddled with for a while and I can mill as fine as a want and never get a stuck sparge. Ever. Cheers!