Ron,
I'd give Butch Searcy a call out there in deepest Boron, CA. He makes the .375 flanged magnum and regulates it for, as I recall 2400 fps. He'll likely have a load or two and might even have pressures.

NOTE: I've got a number of rounds ready to check when Butch finally gets mine to the point that I can shoot it in the white. Have used IMR4350, but well under 80 grains for the 300 grain CEB flat nosed solid and for the 300 grain Swift A-frame.

Best of the Season,
Tim