If you're new to loading precision on the 550 I recommend looking around at ways to improve the way you run the 550. There are some minor things you can do that can help improve performance. I'd also pay close attention to what lube you use on the main shaft, as well as your consistency with physically operating the handle and the "feel" of the press when seating bullets, etc.
Other things you can do:
1.) If resizing on the press, either have a die adjacent to the resizing die that takes some force (mandrel/seater/etc) to offset the resize force. Or you can put a powder die and screw it all the way until it touches the shellplate, so it offsets any shellplate forces enacted by the resizing operation.
2.) If you're going to use the Dillon powder measure (which you can), use a good baffle, and polish the entire inside of the measure (and powder bar) in your tumbler for a couple hours with polish.
3.) Always set up your dies with cases in every position being used, especially with seating and resizing. The other positions can mildly change the seating depth or shoulder set back, etc.
Heres a good article I've used ... (excluding the Prometheus lol)