MattH I have started with 18g doses and then setting/adjusting the grind (omega with large jumps and the c40 with redclix for smaller adjustments)
I do find its either very quick once it starts to flow - or very slow at over a minute.
I think what you’re seeing is the limitation of stepped grinders. One setting may be too coarse for what you want, and the next step over is too fine. This could also be partly due to the beans that you’re using. I’ve found that the lighter the roast, the more sensitive the extraction time is to the grind setting. I haven’t had experience with decaffeinated beans, but from what I’ve read, they are harder to dial in than a non-decaffeinated bean.
I’m assuming that you don’t like the taste of what you’re getting. Although there’s a general target of a 25-35s extraction time that 9Barista suggests, that’s just a starting point, and taste trumps everything. @tompoland says that for him, 40-45s works the best. My general sweet spot is around 30-35s with the beans that we usually use, but I recently had a bag of single origin medium roast beans that wanted a 45s extraction time. I’ve had shots that took over a minute to extract, and shots that were done in 20s, and they both tasted great.
First thing to do, if you haven’t done this already, is to keep a log. Here’s my fancy one from when I had a stepped grinder. The numbers are grind setting, dose, (extraction time), and then maybe a note on how the shot was. I generally just wrote down the grind setting and dose that I wanted to try for the next time based on the taste of the shot.
The good news is that you can mitigate the stepped setting issue by adjusting the dose. Instead of going finer, increase the weight of the beans by 0.5g steps. You can also drop the weight of the beans if you’re too fine, but I’ve had better results by going up on the weight.
Conventional espresso making technique says that the dose should be sized to the size of the basket, and you should use other variables to adjust the extraction. Things are different with the 9Barista, as grind and dose are the only things that can be changed. But it works.
Finally, there’s a nice diagram in the 9Barista instruction book that gives guidance on how to adjust the grind and the weight based on what you’re trying to change in terms of the taste. Make sure you take a look at that.