Yeah, it took me a bit, but getting +-.001 is fairly easy now and repeatable. The bullet variation is the biggest factor now.
I found there were fairly big differences in grouping changing the depth by .003 jumps. I think if you go .01 or .015 jumps you would miss some nice groups, plus I didn't want to go any shorter than I needed to as I'm already jumping a bunch due to the magazine limitation.