Don't have any experience with it. Sounds alot like the old 375 weatherby which was an improved 375 H&H and a well liked round. Weatherby used to chamber it before they came up with the 378 weatherby. The 375 JRS sounds like an excellent round. Just neck up 8mm rem mag brass; easy to form. Or shoot 375 in it? That's nice, in case there's ever a problem finding 8mm brass. "Velocity in 24" barrel for a 300gr bullet will average between 2700 and 2750fps" according to Cartridges of the World.