What's the rifle used for? You'll loose velocity and therefore have a more arched trajectory with a short 16" barrel. For coyotes out to 200 yards you'll never notice the velocity loss. For pdogs out at 400 yards the velocity loss from cutting 8" off the barrel would be more noticible, ie more drop. If it were mine I wouldn't go any shorter than 20", a compromise length.
Also, what's the overall short limit for a firearm from the batf? I think you're still over it with a 16" barrel, but you might want to check to be sure.
Also for the price of cutting/crowning you might consider sending your reciever in for a 22" standard 223 barrel. Just another idea, ultra barrel/bench, standard barrel/hunting. Might cost a bit more getting the new barrel but you'll retain most of the velocity of the 24" bull and have a more balanced lighter rifle.
later,
scruffy