From The Truth About Guns:

Arne Brennan, creator of 6.5 Grendel and other cartridges, designed 375 Raptor in a quest to do for 308 Winchester what 300 Blackout did for .223 Remington. Namely, neck it up to run larger, heavier bullets that deliver both supersonic and subsonic performance in a cartridge that’s efficient from a short barrel, suppresses well, and runs reliably in all the same platforms as its parent cartridge does.