quote]There was a thread somewhere, here, AR, ?, about a fellow who shot an elephant bull with a 45/70 using Garrett's hot load for the Speer 500gr tungsten cored AGS. He reportedly had full penetration on a side brain shot.

A side brain shot is not a penetration challenge at all. A 30-06 with 180 grain Noslers will reach an elephant's brain on a side brain shot.

The frontal brain is difficult both because of the thickness of the brain, and the great amount of trunk that may need to be penetrated before the bullet reaches the skull. Depending on the elephant's position, the bullet may need to go through 2 feet or more of trunk before it even strikes bone. Obviously the bullet will decelerate as it passes through the trunk, and may not have enough velocity to break through the skull if the initial velocity is already low.