Chuck,
I use Federal 215M's in my 500, in fact I use Federals, either 205M, 210M and the 215M in every calibre I load, currently 24 different ones.
Have never had a lot of luck with CCI's, but that's just my observation, doesn't mean to say they aren't any good.
I have found that Winchester Large rifle primers tend to work better for any cast bullet load in the calibres I load cast for. Don't know why, but the groups show a decided preference for Winchester with lead.
Just my 2 cents worth.

DC