Those who contend ft-lbs energy does not measure lethality are at least partially right. The mistake most people make is using the ft-lbs tool incorrectly. Comparing the energy of a broadhead arrow to that of a .30 cal/180g form a .300WM is interesting because both are lethal but the ft-lbs energy needed to make them so are so radically different. That difference demonstrates the problem - using ft-lbs energy alone to compare the lethality of two different projectiles is pretty much a fools game.
That said, give me a .30 caliber/180g bullet of any design and I'll take 2000 ft-lbs over 200 if shooting elk. And I'll take 200 if shooting a rabbit destined for the dinner table.
ft-lbs energy doesn't measure anything directly except ft-lbs energy. That doesn't mean ft-lbs is a useless tool or that it tells us nothing useful. I can think of four very different ways to use a barometer whose characteristics are completely known to me to measure the height of a building - but it really isn't the best tool for the job.
I doubt you barometer would make much of a bullet...
