I looked very hard into the .375 raptor and really wanted to build one. The big problem is there is nothing available to support it be I couldn't even find reloading dies for it.
I was chatting with Kyle yesterday and he offered me a .375 Raptor upper we built a few years ago (we built a dozen or so)... He brought it up not me...
Drop me a PM with a text number (if you like) and I will get y'all connected. I suspect he can get you straight on dies as well.
He is located in Bowling Green, VA.