No matter how fast you drive a bullet of say, 150 grains, it can never be equal in energy to one weighing 250 or 300 grains.
I'm sorry, but this is simply not true.
Any lighter bullet can equal the energy of a heavier one, and vice versa when the rest of the story is considered. Energy is a calculated number, using the variables of mass and velocity(squared). Plug in the numbers and the resulting number can be equal. That's just a fact, and no getting around it.
HOWEVER, that resulting number does not directly tell you much, other than as a comparison to the energy number from a different combination as a relative value.
Obviously, 600 is twice as much as 300, 1200 is twice as much as 600 etc., but that does not mean the real world effect will be twice as much. Many, MANY other variables are involved in that, which are not accounted for in a straight energy computation formula.
Consider this, a 55gr .224" bullet fired from a .22-250 and a 400gr .458 bullet fired from a .45-70 can be loaded to identical ft/lbs of energy.
IDENTICAL
Obviously the velocities will be quite different, but the energy number can be identical.
IF energy were all that mattered, or even if it were the prime factor then there should be little or no difference in the real world effect of both of them, right?
But, there is a difference. And its a difference not shown by JUST the energy calculation. There's a LOT more to it than just the on paper energy figures.
I own both, and I know which one I would choose to shoot a buffalo, or an angry bear....
I hold to the opinion in my signature line, and nothing in over 60 years of my
observations has yet disproven it.