Basic physics and everything I have read about terminal ballistics. In order to have enough energy to nock a target down it would have to impart the same amount of force to you when you shot it, even more when you consider the distance traveled and area of the projectile.

I have shot peices of fire wood with my slug gun using a 600 grn bullet that is supposed to deliver 3,000 ft/lbs of energy and it doesn't even knock it over. How is it going to knock a 150 lb deer on the ground? And why doesn't it knock me down, I only weigh 130 lbs?

We just talked about terminal ballistics here a while ago in the .410 thread with links to data explaining the myths associated with it.

Here is one of them.
http://www.rathcoombe.net/sci-tech/ballistics/myths.html

It talks about exactly what you are describing. Myth busters even did a show on it where they hung a pig on a mount that barely held it up. The only gun that moved it was a 12 guage, and it barely moved it enough to knock it off the hook it was balanced on.

I have seen deer and other animals buckle and drop at the shot, or jump and fall. I have never seen one get knocked off thier feet and pushed across the ground. I used to think the same thing until I started reading about it and tried a few experiments for myself. The truth is a bullet just can't transfer that much energy because of its size and design.

Paul