Actually, getting near 500 ft.lbs. of energy is quite doable in either a Remington 1858 or Colt 1860. Using a Kerr Bullet (225 grains) and 30 grains of 3f 777, I get right at 1000 fps. That is 499 ft.lbs of energy. Swiss 3f and Pyro P are not lagging far behind, they get around 950 fps. With .454 round balls, I get 1100 fps with 35 grains of Swiss or Pyro P, and almost 1200 fps with 777. I could go as high as 32 grains with the Kerr, which would easily exceed the 1000 fps mark. I've done it. Mostly though, I'm just a sissy boy who likes low recoil, and am quite happy shooting round balls at 850-900 fps, and conicals from about 700 to 800 fps. That guy in the video made figuring muzzle energy a chore, here is a MUCH better method that I learned over 40 years ago.
ME= MV×MVxbullet weight grains ÷ 450240
900*900*225/450240= 404 ft.lbs. ME
Simple.
ME= MV×MVxbullet weight grains ÷ 450240
900*900*225/450240= 404 ft.lbs. ME
Simple.