The 550 is a great machine for modest large quantity runs of pistol and rifle rounds.

I have loaded 223 on one but that now moved to the 650, the 550 does my 308-based cartridges, 243, 360, 308, saves having to alter too much come cartridge change time.

The model number is the approximate number of pistol rounds you can load in an hour and I don't doubt it, however I can load 3-400 .223 on the 550 in an hour (using sized and primed brass). The biggest issue on the Dillons is the powder measure, sometimes the powder will bridge and not load into the case, this can be overcome with some polishing and doesn't happen with all powders.