If I calculate [acceleration and mass] I am working out the 'Force' value.
(which results in Newtons and can be converted to ft/lb) 1 Newton = 0.737562149 ft/lb
with that, Does anyone then really need to apply an energy formula for hunting bullets?
Again, go back to school.
Ft-lbs convert to newton-meters, not newtons.
Newtons are a measurement of force. Newton-meters and ft-lbs are a measure of energy.