came directly from Dillon.
I bought it used, with quite a few quick-change setups and accessories.
650 ...auto indexes, has the space for the powder check die ( for the added piece of mind, in terms of safety alone, I'd take a serious look at the 650) - and install and use a powder check ...
My powder check is done with the tool located in my eye socket.
Powder drops right up front on the 550, and it's easy to see if the case has an appropriate charge.
The manual-indexing of the 550 doesn't really hold you back. A lot of 550 users even claim to be able to run their presses as fast, or faster than, a 650; because you can run the ram faster, without the auto-index feature slinging cases around.
The only real handicaps with the 550 are: The number of stations (if you're a fan of powder check dies, lockout dies, etc). And, the lack up support for automation -- all you can do is add a case feeder that's a bit hokey.
But, if 4 stations are good enough for you, and you don't plan on trying to get a bullet feeder... the 550 is a good press.
The lack of auto-indexing also makes the ram stroke smoother, and makes for quicker/easier adjustments when setting up a new quick-change unit.