doesnt matter the Ft lbs, Round balls have very little by the time they reach 100 yards. They just basically bore a hole through the animal and expand very little unless they hit bone.
100gr 2f black powder and a 490" ball has under 400 ft lbs at 100 yards. But like i said, all that Ft lbs needs to kill such and such is for the modern bullets that are hard to expand and normally for centerfire rifles.
You can kill an elk with a whole lot less than the recommended minimum of 800 ft lbs.