H4831sc is a good choice! I did a work up in mine with the 185 berger juggernaut OTM. I don't have specific experience with the 181g Hammer bullet. If it were my rifle, I would start at 66g H4831sc and work from there with a reliable chronograph. JECustom probably knows a bit more than I do. Maybe he would be willing to share some more data directly with you.
Since you are working with a 30/338WIN I imagine you probably know what your chamber is. There are several different '30-338WIN' chambers out there and there isn't a standardized chamber, as far as I know. Sierra has some published data specific to 30/338WIN using a 338WIN case directly necked to hold a 308 bullet. Also, 308Norma mag data can also give you a place to start, but that's about all I'd believe. With heavier loads and heavier bullets the differences between those start to show up. In my experience, 30/338WIN will generally take a bit less powder to get to a specific velocity than 308Norma, especially if you are using heavier bullets and going after top velocities. Also, it won't be quite able to duplicate 300WIN velocities, but it will get close and use less powder to do it.