Ordinary CCI 250's work just fine in the .375. I even use them with 4064 and 4895 in that case, as well as the .375/06IMP.
: The ballistics are virtually identical in the smaller case and the larger case works better with the mag primers. There is no need for the Fed 215's although they'll do just fine with the slower vburning stick powders, and ball powders as well.
; If ever going hunting in colder climates, you will need the extra burning time of the magnum primer to ignite slow burning powders.
; Normal primers, for me, don't cut it when using powder charges over 65gr.