For some reason i have a bad itch for a 16" pistol cal. upper for my AR15, i am thinking of a 9mm because ammo is dirt cheap, easy to reload, its a fun round, do some small game hunting with it.

Does anyone have this kind of an upper setup already, what do you like/ dislike about it, what cal would you reccomend/ and why, what brand upper/ mags... (or anything else you can think of)?