If I had a lb of beans for every time I failed trying to get my Bullet to do what I wanted it to…
It does take time with a new machine, new technology, software controls, etc. It is hard coming from success on previous roasters for years into a new roaster and finding that things don’t work the same. The principles of good roasting techniques don’t change, but differences in roast equipment can be a challenge to master.
Out of curiosity, are you on one of the new V2 Bullets or its predecessors V1, V1.5 (which I have)? I ask that because all of my experience on the Bullet comes from using a Bullet 1.5. It occurred to me that there could be some differences on a V2 that I just don’t know about.
Back to your current progress. In your latest graph, there is still some opportunity for roast management improvement.
I see that your Preheat is now set to 455F (good stuff).
Try going to P8 at the 1-minute mark (instead of waiting 2mins into the roast).
Drop to P7 immediately when you see Dry-end (or the “YW” point on your graph). Keeping the Heater at P8 all the way to just before 1st C began to grow is applying too much heat to the beans during the period from Dry-end to 1st C. It is also what causes the “flick” (or spike) in the ROR at the ~6min mark.
When your bean temp reaches 176C (350F), immediately drop to P6. This drop helps further reduce the roast temp in anticipation of the beans going exothermic as they do right before 1st C.
When you hear the very first snap of 1st C, drop the Heater to P5.
Unless you are shooting for a dark roast that produces a lot of smoke in the drum leave the Fan at F2 throughout until Dump (for now). One qualification though: My Bullet does not have that Fan range change that Aillio implemented several firmware releases back. So, F2 on my machine could be very different than F2 on your Bullet if that firmware change is in your Bullet.
The Mill City videos were the baseline of how I solved this oft encountered problem that you are having with this new machine. Armed with good bean development knowledge, it then becomes a task to get the Bullet to accomplish it for you.
One last thought. Maybe try one of the RoastTime profiles that some of the other veterans here have shared. That might be an easier baseline way toward finding what tweaks you may have to make to adjust the outcome to your particular tastes. Keep at it because “there is light at the end of this tunnel”.