I find that velocity to be incorrect,,the .300 Wby with a 26 inch barrel will do 3540 fps with a 150 gr.so the 30-378 must have a velocity of 3900-4000 fps with the 150 gr- 165,and with a 28 or 30 inch barrel !I think the .30-378 will make 3550 fps with a 180 gr. bullet,and no doubt !
3550fps is obtainable with a 150gr bullet in a 300 ultramag with a 26" barrel and quite reasonable pressures.Based on that the 30-378 should deliver between 3800 and 3900fps with a 150gr bullet and a 30" barrel.My own 300wby mag with a 26" barrel would do no better than 3400 to 3450 fps at reasonable pressures.