typically 2 gallons. i put the grain in a bag, and put this in my igloo cooler. i use the electric kettle to heat 4 gallons of water (right to the brim) and what i don't use in the mash i keep in another pot or cooler if needed. then i just drain the cooler back to the kettle to target about three gallons. boil down to 2.25. ish. still working some of the kinks out.
I do nearly the same thing. I don't have a mill, so I'm at the mercy of where I get my grains crushed. I generally hit 80% brewhouse efficiency when I get my grain crushed from NB or AHS. The guy at my LHBS insists
that I don't want to crush my grain twice and that his mill gap is set perfectly. (He also insists that I need to move up to fly-sparging when I "get serious" about doing all-grain) I generally hit the low-70's efficiency when I have to get my grain from him.
FWIW, I've never noticed any astringency in my beers regardless of how the grain is crushed. Of course the majority of my beers use quite a bit of hops, so I don't know if I've even brewed anything where I could distinguish much astringency from the grain versus hop tannins.