I have a Remington Sendero 300WM and shoot the 200gr Accubond and Sierra Match King in it.

Here was my strategy:
1) Determine length of chamber. Seat bullet long, mark all of bullet with black permanent marker. Seat bullet progressively deeper until it will just chamber without engaging the rifling (which makes marks in the marker). This is maximum bullet length. I backed off 5 thousandths I think, from that. Some bullets like more "jump" to the rifling than others. If you are seating with no idea what jump you have, it is hard to make accurate loads except through sheer luck.

2) Conduct a ladder test at 300 yds. Starting with a low load, shoot a series of loads identical except for powder charge at incremental powder charges (I did .2 grains difference I think). Use a very, very steady rest. 100 yds won't work either. You should see a series of "nodes", where slightly higher charges won't change POI much but then it will jump and again stay consistent for several increasing charge shots. Within each node velocity is about the same; you can then test 3-5 shot groups at each charge within the node of desired velocity to pick the most accurate one. Note you'll have to do with with each new bullet type.

3) Play with seating depth to fine-tune accuracy. I did not bother with this since I was at 1/2 MOA after steps 1 and 2.

I love the Accubond. I would recommend it. However, I question the logic of anyone who told you a 180gr partition was only meant for small deer. That bullet is a fine elk bullet. But for bear I'd go with the 200 Accubond.