My wife just traded her 308 for a 6.5 CM. The guys I work with just cannot understand why she give up "all that power " of the 308. I understand that sectional density makes a big difference in penetration. I also know that it is the ratio of the diameter to the weight of the projectile. I cannot get it across to them that a 140 6.5 will penetrate better than 150 308 at the same speed and same construction. Any good way to explain this to people who refuse to think or listen. Their argument is that the bullet is heavier ,so, has to be better. For all practical purposes it makes little or no difference. Nothing up to and including elk are going to know the difference at the distance she is likely to shoot. Just trying to convince the lads she hasn't handicapped herself.