Yep, that wasn't the issue. I think I have two very big problems:
1. I'm trying to hit a specific shot weight (1.1 oz. shot from 0.56 oz. grounds, perfect 2:1 by weight) on a 22 second timed extraction. I'm not sure this is a realistic goal, it may be better to extract a 1.1 oz. weighed shot, and just see if I can hit the magic 20 - 25 second window. This is because the pour rate is much higher at the end of the shot than at the beginning, just a second or three foregiveness can make a big difference in shot volume. I originally chose to do volume per time, because it's so much easier than trying to jam a scale under the shot glass on the machine.
2. I am having issues with getting repeatable measurements of my 18 oz. portafilter and holder. I am trying to measure a 0.56 oz. fill on an 18 oz. hunk of metal, the coffee is only 3% of the weight I'm measuring. If the scale is ±1% accurate, then my coffee charge is varying by 33%. I also found that the position of the portafilter on the scale makes a difference of a few %, enough to throw huge inaccuracy into the actual coffee weight measurement. This position issue, and later resolving it, is the difference between the "accurate" data points and the earlier "questionable" data points.
There are probably a half dozen other smaller problems with my consistency, but these are the big'uns I see. That said, here is the summary of the data I collected:
View attachment 246465
So, ignoring the "questionable" data for a moment, and just focusing on the "accurate" data, note that I got a shot size of 1.73 on a grind setting of 14i (=14.89), so I turned the micro ring down to 14f (=14.56) and my shot got heavier! Knowing that couldn't be right, I turned it down one more micro setting to 14e (=14.44), and got a too-small 0.83 oz. shot. WTF?
Somewhere in there, I also did two more shots at 14d (=14.33) and got weights of 1.13 and 1.56 oz., not exactly super-consistent.
The trend line is pointing toward a 14b grind setting, but I never got there, I ran out of the bean I was using.
Earlier, during the "questionable" measurements, I started off with a bunch of shots that were a bit too small (0.7 - 0.9 oz. at 22 seconds). Since the micro ring was already as coarse as I could go in the 13's, I clicked the macro ring once to 14i, and pulled a 22 second shot that came in at 0.4 oz! That made no sense, I should be getting bigger shots on the same timing, with the coarser grind. Thinking I must've screwed up, I pulled a second, and it came in at 2.3 oz., almost 6x the first. I decided to do a third on this same setting, and it came in at 0.7 oz, still smaller than the shots I was pulling on the finer 13i grind.
I'm not sure what could be causing this. I have three more bags of beans (at $14/ea!) coming tomorrow or Friday, and will experiment further. I'm thinking of changing to just pulling by weight, even though it's a complete PITA, and just ensuring it lands in the 20-25 second window. I may also pull some shots with the Virtuoso grinder, to verify I can still do consistent shots with that, I believe I could before.