Try using the Winchester Ballistics Calculator in the 1st link below.

Enter the 2 different calibers you want to compare, the bullet type and weight. Press the "Shoot" button and the comparison is detailed. Try to use the same bullet types and weights for best comparison.

I compared the .30-06 and .308 using the Ballistic Silvertip in a 168 grain bullet. The ballistics for the two are nearly identical. The Axial View shows the point of impact on the target.

This ballistics calculator is cool because you can change the variables such as the distance, crosswind speed, temperature, etc.

http://ballisticscalculator.winchester.com/

http://www.winchester.com/LEARNING-C...alculator.aspx