I have no particular interest in debating the merits (or otherwise) of hunting with catapaults.
The one thing I will say though is that the idea that 18ft lbs of energy is sufficient to ensure a kill in a non-lethal zone and without a well aimed shot is very, very odd to me.
Whilst this may appear to be "half as much again as basic air rifle", I will invite a different comparison.
Lets try "one fifth as much as a .22 rimfire cartridge....with an absolutley rubbish comparable ballistic coefficient". A .22LR rimfire round imparts about 100 ftlbs of energy. Granted it has different terminal ballistics than a .44 ball, however the idea that "a hit = a kill" on a .22LR is clearly nonsense. I cannot see how a round carrying less than 20% of the power, with lower range and less accuracy would impart such certainty.
As I said, I have no particular interest in the merits or otherwise of catapault hunting, however, I can. with some assurance, state that a hit in a non lethal zone, using a .44 ball carry 18ft lb of energy (and bearing in mind this energy decays FAST over range) would not necessarily equal despatched prey.
Red