If you have time work up a load with the 180 partitions at 3100 fps(24" barrel).
Give you much more margin for error and more power if you need to take a longer shot. I prefer the 200gr partition for elk.
With the 200gr sighted 1" low at 300 yards, I am 12" low at 400, 30" low at 500. This gives me a 100 yard sight in of 4" high. I have never shot at a bull more than 150 yards away but it is good to be prepared for that once in a lifetime opportunity at a monster bull on public land unguided if it should happen to be at long range.
A good sized bull is appx. 30" top of back to bottom of chest, that is a big target. 1/2" accuracy is not required, lots of power with a good bullet is.

Given a good broadside opportunity the 150 will work fine, with a marginal angle you will wish you had more bullet.