I think you can safely use the Federals in your Lee.
Thanks for your replies. I did. I loaded the tray 10 primers at a time, i used goggles, i put on leather gloves, AND, i stood behind a door and extended my arm with the priming gizmo to the other side of the door.

It worked, and nothing went wrong.
But, the slick and slippery handle and body of this Loader makes it somewhat tricky for me to learn how much pressure to put on the handle. I also noticed that half of the primers where not completely flush with the case head or bellow, and that got me worried. So, i switched to priming on the press.