I'd start with an Armalite 16" barrel. They're fair priced, chrome lined and mid-length gas. I've shot the hell out of my original (factory built) carbine.....with all types of ammo. Same barrel type was used on one of my carbine builds. And that one I use as my beater.
Or, you could go with a Noveske barrel. Ranier has a few, but not in the medium contour that you're thinking about. They're a little more on the cost side, but you can't go wrong with any of their barrels. I've got a couple of their barrels on different builds (including their 12.5" Leonidas barrel for my 10 SBR).
Here's the beater. She has a couple thousand rounds through her.