A lot of things go into reloading 5.56 ammo. Things like what type of firearm are you using it in? Where are you getting your brass? What type of press/dies are you using? See below answers to your questions and feel free to ask more:
5.56 uses small rifle primers. Some people will say to...
First you need to confirm what calibers you are loading and what volume you want to reload. I have a Dillon 1100 and I still use my single stage press for different operations.
I haven't used a 550, but I've heard good things about them. The problem with any progressive press is that there is...