Yup. Different bullet designs respond differently to going through the trans-sonic range. Drag changes throughout this range, and in turn the BC changes, as well. Some bullets are somewhat, or even significantly, destabilized and the BC consequently goes way down.
I use a 5700 Elite as a secondary ballistic solver, but still rely primarily on the Ballistic:AE app, as I have a lot of experience with, and trust in, that app. The concept is as Rick mentioned. I haven't played with DSF calibration, but it makes sense to me that if you acquire a DSF data point at a lower MACH number, DSF data points at higher MACH numbers will be superseded by the value acquired at the lower MACH number. I'll have to play with it to confirm.
