Be really careful with 150 grain bullets. Most of them out there will literally explode when they hit and half of the time, they will not exit. Sort of a shrapnel grenade to be honest. I would look at 165 partitions maybe. They will hold up and there are some good 165 grain bullets out there that would work well. Most 150s start to come apart in a 300 Win mag, let alone a WBY. They are great for 30-06 and 308s though. When you deal with guns that produce the velocity that the WBY can and the pressures, you have to start really looking at bullet construction, not just weight. The 165 will shoot flatter at extended ranges than the 150 as well, holds its steam better. Doesn't seem like 15 grains makes a difference but its pretty noticeable.

Has anyone else shot it that is comfortable with the gun just to rule out a flinch? The blast on the big guns is enough to make some folks snatch the trigger like a shotgun rather than a rifle some days. May be worth trying if you know someone that is truly accustomed to shooting heavier kicking rifles just as a check.