With the 375 Wby still around, and the 378 Wby hammer thriving I couldn't figure out why Remington felt they needed to introduce the 375 RUM. There is absolutely nothing wrong with the 375 RUM as far as I can see. It just doesn't do much more than the 375 Wby and a bit less than the 378 Wby.
My FN Sako in 375 Wby gets an honest chronographed 2,933 FPS with 260 AccuBonds. And, it does allow me to shoot 375 H&H ammo in a pinch.
When we could buy Remingtons in 375 RUM for around $650.00 I sure could see some reason for them; they were a great Hammer for a moderate price.