As usual..Pull and Mark is correct. When he says the American primers will fall out of the Rio hull, he ain't kidding. If you ever use a Rio primer in a hull and try to use a Winchester, Fed, Rem, or Cheddite, it WILL fall out IN THE LOADER before it goes all the way around the turret.
On the other hand, I load a lot of Federal papers and after a load or two they begin to leak around the primer. I use Rio's after one loading and toss them. Works great, no leakage.
p.s. I bought 10,000 Rio's in a real deal several years ago and everybody said I was nuts (I am by the way) but I gave $.80/100. That's right $8.00/1000. Looks pretty good now!