The Citadel (made by Chiappa) has gotten some bad reviews. I really want a 9mm carbine but I took a pass on the Chiappa.
https://www.youtube.com/watch?v=2zv8KgSUPso
I've got the .22 caliber version of this rifle and like it a lot. It's got MORE polymer on it. This guy seems to think polymer is a bad thing, not necessarily. I can confirm the trigger is quite stiff, but very crisp. Should be lighter, though. But, I'd rather have a stiff trigger than a creepy one.
I've put 500 rounds or so through the .22, eat's 'em up. It's picky with what it's most accurate with, though. The sight on the .22 is plastic and the M1 original sight can be fitted to it which I might do in the future. I really don't concern myself with stuff like a non-functional bayonet lug.
I'd get the Chiappa 9mm if I wanted an auto pistol carbine just because I like M1 Carbines, the looks. I don't own the original for the same reason I don't want a 9mm, worthless round for anything I do, too big for squirrels, too little for deer/hogs. Same for the 9mm, but the .22 plinks without need to police brass for reloading and is handy in the field for small game.
Oh, he was having trouble with the sight. If he were to remove the aperture, he'd find a set screw under there. When you remove the sight, though, you need to be careful to capture the little spring and detent ball under it. I'd apply some loctite to that set screw before tightening, be sure it didn't back out again.