While widely accepted it’s also stupid. I think that may be what he’s getting at.
Why is it stupid, it is a good solid axiom, if you are asking that means you NEED general info If you are an experienced Shooter / Hunter then you have your own opinion that is formed over the years
I am not answering for him but I use impact velocity along with a bullet of fair enough construction and weight to get through bone and vital tissue. Energy is hard to measure since a ML or 45-70 will never make enough energy but they work just fine when you apply the right bullet. Just my thought on it.
Okay lets try one more time since I am a 45-70 shooter also and my Marlin GG shoots my handloaded 405 gr OT Lasercast at 1450 fps which means that I am WELL within that general rule of 1500 ft/lbs out to a Black Timber Elk Long Range shot of 125-150 yards
PS; I already mentioned that the bullet must get into the Vitals with my first post so you are now simply repeating what I already said, much appreciated