thats about what i'm seeing. hot light 9mm form a 16" is giving about 480-500 ft-lbs of energy at muzzle.
the standard load from a 357sig from a 4.5" barrel is about 490 ft-lbs. ( not counting light loads which dip down into 9mm p+ loads)
my guess is a 357 sig would do 700 ft lbs from a 16" barrel --a hell of a lot of punch from such a small package--LOL
the problem with the 357 sig is expense, but it would make a hell of a pistol powered carbine--
take a look at the ballistics --
BBTI - Ballistics by the Inch :: .357 Sig Results