15ft*lbs is required to secure a spark plug.
I don't know about all these foot pound rules... but you have to look at it in perspective to the caliber.
Now if I had a 300 grainer in .45 that was going 900fps.... that is only 550 ft lbs. But even that slow... it is going to penetrate and kill any thin skinned animal out there at handgun range.
If I was to take my -06, and drop my 165 grain bullet down to about 1600 fps, then I would have your rule of 1000 ft*lbs. The thing is, I don't want a bullet that small going that slow. A .308 caliber at 1600 ain't much for penetration... Now if I took that same bullet down to the energy of that .45 load... it would be going about 1225fps... A 308 at 1225? I don't think so.
So you take that same speed and weight, you throw it in a 357 mag. Now at close range with deer sized game, a .358 caliber would work with 165 grains at 1225fps. I still wouldn't try it with the .308 caliber bullet though.
Now lets just say you are right, and we need 1000 fps and 1000 ft lbs.
We take our .45, and we throw the bullet out there at 1000fps and 1000ft lbs.
Problem: we are now shooting a 450 grain bullet. I don't know if you have looked around... but there aren't that many 450 grain bullets made for the .45.
So with this one, I am going to have to revert to the same thing that GB said. Quit talking about the rules and what the book says, and look to experience of hunters who have killed lots of animals with these "too light" loads.
I guess I was brought up with the rule 1000 fps and 1000 ftlbs was minimum for deer. I don't understand the fascination with trying to kill deer or any other animal with the lightest possible load.
And the light load has nothing to do with any fascination. In this situation, it is about the health of a man's wrist. In any situation, lighter loads are more accurate due to less influence of recoil. And also, these lighter loads cause less fatigue when practicing, making it better practice. A better shot with a lighter load? Does that make up for a deficit in energy? Yes it does.