You may be able to get away with running the 270 grain Badland Precision super bulldozer. It has a .401 G7 that I have been running, and with the velocity you can get over a 300 grain berger, it is right on it's heels for wind drift. If your shooting a sierra 300, it has significantly less wind drift. May be worth checking out. But if it wouldn'twork, the 240 Super bulldozer may be a good option, it has a .710 G7 (vs .685 for the 250 Berger) and would be an awesome flat shooting hunting round, with less wind drift and likely more energy than the 250 Berger much past 400 yds.
I have loaded the badlands in a couple different rifles, and they have given me fantastic accuracy, very easily.
Length: 1.979 BC (G1): 0.803 Twist: 1:9 Price: 50/BOX
badlandsprecision.com
Length: 1.828 BC (G1): 0.710 Twist: 1:10 Price: 50/BOX
badlandsprecision.com