Depends on many factors. I need more info.... game, purpose, distance, calibre, grain, etc.

In short, light skinned / boned animals require a lightly constructed bullet. As the animal's structure or weight increases, the stronger the bullet needs to be in order to achieve:

1. Adequate penetration to reach and go through the vitals.
2. Sufficient expansion for shocking power.

Using a bullet that's too strong for the intended game will result in FMJ-like performance, with complete penetration and very little expansion.

Conversely, using too light of bullet on heavy game will result in less than desired penetration and over-expansion (HP like performance).

Selecting a bullet that's suited for the intended game is often overlooked and many times more important than choice of caliber.

* Shot Placement
* Choice of Bullet
* Choice of Caliber

I have always used Rem.'s corelokt 30-06 180gr. ( they come 20 in a box I only use 1-2 a year so they last a while) This year I shot my first bear and was a little nervous about bullet selection. Hit him at about 100yds went all the way through( bear was about 200lbs) didn't hit any bones was a direct hit through heart and lungs

I use 130gr. 270 winchester ballistic silvertip for deer and have shot deer from 75 to 300+ yards and never have had one run on me. And I wouldn't say that I'm a sharp shooter.