I have both the 550 and the 650. The autoindex isn't what slows down the 550, it's lack of a casefeeder. (Yes, I know they make one, but I hear it's too unreliable, whereas my 650 doesn't have problems).
Yes, the 650 autoindexing wants to sling powder, and I use TG which doesn't begin to fill the case. I fixed this by seating in station 3, and I put bullet atop case as the case is approaching that station (hasn't stopped auto-indexing yet). Putting bullet on top prevents powder from getting slung.
Don't turn your back on the 550 because of lack of autoindexing, that is NOT what slows you down, believe me. I've loaded 40,000 on the 550 and close to 15,000 on the 650. I just hated having to release the handle on the 550 to insert new case into shellplate. That is the true slowdown.
Ron M. ('59 is my birth year)