Accuracy does not affect how many times a multi-hit move will hit.
Where did you learn that accuracy will give it a higher average power? I'm sorry to say, but the amount of times a multi-hit move like Bone Rush is based on chance. Accuracy will only make it so whether a move will hit or not, and if not, moves like bone rush will not hit at all. The only thing that can affect this other than chance is the ability Skill Link. However, there are moves like double kick which will always hit the same amount of times.
Hits Prob. Power
2 3⁄8 50
3 3⁄8 75
4 1⁄8 100
5 1⁄8 125
Hope I Helped!
Source: http://pokemondb.net/move/bone-rush