I load 223 on a Dillon XL650. To be honest, I have never bought commercial brass for that caliber and that poses some special problems in reloading it. Crimped primer pockets are the main problem with once fired brass. Getting the primer out with out sticking the case is another problem!
Case lube and a pocket tool, there are many ways to do it, are necessities when loading this cartridge.
Here just a while back there was a thread on the other forum about case lube. People came out of the woodwork with ideas and experiences. Many homemade case lubes have been employed. I have used Mink Oil for boots, Hornady spray, Imperial Wax, RCBS II, Pam vegetable spray, Break Free and other things that I can't remember right now and not all of them work well on this cartridge. I can tell you the Hornady spray isn't going to get used again! The ones that have worked the best, and you don't have to use it on every case, are the RCBS II on an old Lyman Pad and Imperial Wax.
Sometimes I switch between the two as I am resizing them.
If I am reprocessing my own brass I can just clean them and run them on my XL650. If not, I have to run them on the single stage first.
I too load the 55gr bullets. I use BLC-(2) because the case is less full and the XL650 has automatic indexing. If I use an extruded powder they are too full and slosh out as the table indexes.
You won't have that problem with the RL550 as it is indexed by you manually!
Have fun.