Originally Posted by Wikipedia to the rescue!

"A standard .30 carbine ball round weighs 110 grains (7.1 g) m and has a muzzle velocity of 1,900 ft/s (580 m/s) giving it 880 foot-pounds (1,190 joules) of energy. By comparison, a .357 Magnum revolver fires the same weight bullet from a 4-inch (100 mm) barrel at about 1,500 ft/s (460 m/s) for about 550 foot-pounds force (750 N·m) of energy, though it is important to note that the .357 bullet is larger in diameter (caliber) and is normally an expanding or hollow-point design.[1] The .30 carbine was developed from the .32 Winchester Self-Loading used in an early semi-auto sporting rifle; both rounds are comparable to the .32-20 Winchester round used in carbines and revolvers."