For Grizzly with the 30-06, I wouldn't pick the 220 grain bullet unless I was sure the range would be short. The 180 X bullet or 200 grain Nosler Partitions are a much better choice. I have never used the 300 RUM but Have used the 300 Win Mag and Weatherby Mag. The difference between the 300 Mag and the 30-06 is about 80-100 yards. The Energy and Velocity of the 30-06 is about the same as the 300 Win Mag at 80-100 yards shorter range. Both have taken many grizzly and will probably continue to do so.