[BrewBama]

So... I have a question:  if I end up within a point of pre-boil SG despite getting different readings throughout the mash, is that considered a consistent process?

Previous brew (cooled to room temp)

20 min 5.40 pH 1.057
40 min 5.41 pH 1.064
60 min 5.42 pH 1.067
80 min 5.37 pH 1.070
90 min 5.37 pH 1.070

2nd run 5.48 pH 1.028

Pre-boil 1.047

Today:

20 min 5.52 pH 1.050
40 min 5.43 pH 1.060
60 min 5.43 pH 1.065
80 min 5.35 pH 1.070
90 min 5.38 pH 1.070

2nd run 5.47 pH 1.030

Pre-boil 1.048


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[denny]

I'd say so, but it's up to you.

[ynotbrusum]

That is pretty consistent, I would think.  Otherwise, you are chasing a unicorn...blending is what the big boys would do, but I would just drink the beer.

[Robert]

Anecdote.  When I lived in England, they didn't yet list the ABV on beers (must be an EU thing.)  The pump clips in the pub would give the OG instead.  Typically something like "XYZ Best Bitter, OG 1039-1044."  The brewers -- the big ones -- apparently saw that kind of variation from batch to batch.  If they thought that was consistent enough... TIFWIW. 

If I were getting results on the order of yours (and I do) I'd say (as I do) it's as consistent as could possibly be registered, being within the margin of accuracy and resolution of my instruments, and also possibly accounting for sampling error (depending on method) given inevitable unevenness within the mash bed.

(When I see wort density rise at different rates through the mash steps between two batches, the only concern I'd ever have is that it might show up as a difference in attenuation limit in the wort even if the final density is identical -- I might expect a different sugar profile.  But I've never even seen that; fermentability is similarly consistent too, within my ability to measure it.  Maybe because all of our malts are so enzymatically "hot," as Denny often points out.  Makes me question the value of step mashing sometimes,  but that's for another topic.)