.600 Nitro Express- Case length 3" factory load is around 110 grains of powder with a 900 grain FMC bullet velocity about 1,850 with 6,840 foot pounds of energy. For a time this was the most powerful cartridge going how ever it now has been regulated to a "also ran" category by such cartridges as the.577 T. Rex, .585 Nyata, the .460 Weatherby and the .700 Nitro Express.
The book Cartridges of the World has a write up on the .600 you might want to check it out. The .600 is a double gun cartridge and rifles, at least the good ones run $100,000 and up if in good condition and weigh in at 15 pounds or more and you do not want them much lighter. All of the big thumpers I mentioned are far more gun then all but a few shooters can handle or shoot with any degree of accuracy.