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When it comes to what that bullet will do to an animal, thinking about ft-lbs energy is just adding something for the sake of adding it.
What does it matter how many ft-lbs energy it has if it creates the wound that you want? If it doesn't create the wound that you want, than why does it matter what the energy is?
It almost sounds like you're trying to use ft-lbs energy instead of impact velocity to determine something. Does Northfork bullets state that you need a certain ft-lbs energy for bullet upset and expansion?
ft-lbs energy DOES determine something. It determines the maximum amount of work (tissue/bone destruction) that can be done. A given value for ft-lbs also defines very specific combinations of bullet velocity and mass. For any given bullet velocity or mass, there is only one combination that will give it a particular amount of energy.
What it does NOT determine is the ACTUAL amount of work that will be done. You keep harping about velocity, but velocity alone determines nothing but velocity. Billions of sub-atomic particles pass through your body every second at near light speed, yet they do you no harm because they have such low mass. In other words, they have very low energy. When you talk about the destruction possible with a certain velocity, you also need to talk about the mass of the projectile. For a given velocity and mass, both momentum and energy (ft-lbs) are pre-determined.
Again, a given bullet's ft-lbs energy determines the maximum work (destruction) that it can do - regardless of the bullet's velocity or mass or construction. How much ACTUAL destruction is done depends on the amount of energy transferred to the target (the amount of work the bullet performs). This in turn depends on the time span of the energy transfer, the construction of the bullet and the types and amount of material in the target that the bullet passes through. 100,000 ft-lbs can be instantly and spectacularly lethal or it could be applied but never even noticed if applied over a sufficiently long time span.
If a bullet creates the wound I want, it clearly has enough energy to do so. If it does not create the wound I want, it MAY not have enough energy to do so or there may be other issues which prevent adequate transfer of the energy it does have.
Suppose you were hunting elk and had a choice of two cartridges, one which wioud deliver 2511 ft-lbs energy to the target and the other 374 ft-lbs. Suppose you also know one has an impact velocity of 2052 fps while the other impacts at 1568 fps - but you don't know which is which. You know nothing else about the loads - not the bullet diameter, construction, weight or velocity - nothing. Would you hesitate even for a moment to choose the 2511 ft-lb option?
What if you were offered a different choice between two different cartridges, again for elk. Say 125 yards. You know one has an impact velocity of 2052 fps and the other at 1568 fps. You also know one has an impact energy of 2511 ft-lbs and the other has 374 ft-lbs, but you don't know which is which and you know nothing else about them. In that scenario you might make a rather poor choice because velocity alone tells so little.
Like other tools, including velocity, energy is a tool that can be used and abused.
