IMHO,I feel that there is a very important factor that has been lost in all this talk about energy,I don't mean on this forum,but in general,gun magazines etc.
Energy is a wonderful thing,without it,a bullet can't do it's 'work'.
For it to do it's work,it must have a Sectional Density that allows it to 'plough' through animal tissue,with the energy we are talking about to impart as much destruction allowable.Too much,and the bullet may over expand causing the wound to be too shallow,not enough,and the bullet may not expand and pass through with little tissue destruction.
Sectional Density HAS to be the first thing you look at,in any cartridge,to see if it's capable of taking the game you're after.
If you look at the formula used to get energy figures,it is afterall only a mathematcal equation.
It's a hypothetical number that doesn't take into account bullet performance,only it's weight,which really means nothing,and doesn't calculate in the bullet's SD.
All that said,this is my favourite saying:It doesn't matter what you hit 'em with,it's where you hit 'em,and what BULLET you hit 'em with!
The bullet does ALL the work,not the energy imparted to it by the gun.
On a side note,when Roy Weatherby was designing his cartridges,he ran into a lot of problems with bullet failures,the only reason for this was the fact that his cartridges pushed 'em TOO FAST for them to handle it!
This a good lesson we should all take on board.
CHOOSE THE RIGHT BULLET!