Get a 550b. It's a manual index. Allows you to stop the process at any time if there's an issue so you can fix it. Plus it takes a whole second to index it so its still fast. I had an auto index at one time but after I got the 550 i fell in love. Only plus side of a 650 you put an auto bullet feeder on it. To me it's not a big deal. On a good day I can do around 250 rounds an hour which is fine with me. Different strokes for different folks though.