Your Tikka .300 WSM is an excellent choice for black bear. For bullet selection, the 180gr Accubond is more than adequate if it shoots accurately in your rifle. If you want extra margin, the 200gr Partition is a proven performer. Focus on shot placement over max velocity; a well-constructed bullet in the lungs is decisive. Your aim point analysis is correct – right behind the shoulder for a double-lung shot is ideal. Enjoy your hunt.