For a .243 to take whitetails with? What would you consider the edge of being out of range? thanks in advance, trying to decide on calibers

If you are shooting a 100 grain bullet, about 400yds. This is where most 100 gr bullets are still getting 800 to 1000 foot pounds of energy. I'm sure that range could be extended with different bullet types and/or different handloads.

Thanks