I agree and disagree with Boomer...
Will I purposely hunt moose with a .223? Hell no!! I've got many more rifles that are more suited to the task.
If I was sitting somewhere with my .223 and TSX bullets and a moose wandered in front of me at 30 yards while I had a moose tag? Hell YES, I'm taking the shot.
As I mentioned before, the .223 TSX wound channel and a 30-30 wound channel are very similar, in the tests I've done with wet newspaper, dry newspaper, wood and comparing shots on live animals.
I don't want to get into a debate about ft/lbs or sectional density or whatever else hunters dream up to measure killing power, but I think that it's difficult to argue that a 30-30 or any cartridge that gives similar performance won't kill a moose at reasonable range.
Then there is the "how well do you shoot what" argument. If someone can't handle a bigger gun, isn't a smaller gun with good bullets and good placement a better idea?
.223 for moose? No, if you have a bigger gun. Yes if you can't shoot a bigger gun, you have good bullets, good shot placement and the distance is short. Not my first choice by any means, but you can make it work