I am about to start my new build. Here is what I am thinking I want so far: 18" barrel, threaded for muzzle break (can attachment), in .223 wylde. Other than that, I am still researching what brand and other options I should consider. I would rather get a bunch of opinions and research them and "cry once" now buying the right barrel than having issues later.

I have read that Noveske, Wilson Combat, White Oak Armament among others make nice, accurate barrels. Anything else you would recommend that I should check out?

I was thinking of getting a heavier barrel. What contour or diameter barrel would you recommend? Other than weight, are there other things I should consider?

What length gas system? What are the pros and cons for using a rifle length, carbine length, or mid length on an 18" barrel?

Thanks for any and all help and suggestions

Noveske, WOA, and Wilson Combat would all be great choices. You also may want to take a look at the Rainier Arms Ultramatch line (uses Shilen blanks), Krieger, Lothar Walther, Lilja, just to name a few. For the best of the best-Bartlein barrels would get my vote. As far as gas system goes, you'd want to look at either a mid length or rifle length. Most offerings for an 18" barrel would come out as a mid length system. A rifle length gas system may produce a little bit softer shooting rifle, but is not necessarily any better than a mid length.

AR15-Performance is another great option, they offer an 18" fluted (rifle length) SPR barrel (.223 Wylde, 1:8, 5R) that's melonited...I love mine.

They are closed until 1/19/2015 for vacation.

i have had great results with this barrel
http://shopwilsoncombat.com/Wilson-Combat-Match-Grade-Barrel-556-NATO-Recon-Tactical-18-1-8-Twist-Stainless-Fluted/productinfo/TR-556RC18F-18/

I have a 19" barrel from Harris Barrel Works out of Centennial, CO that will shoot 1/2 moa or less all day long.
The barrels are made in house and are very high quality.
Check them out at: http://www.harrisbarrelworks.com/index.html
LOT's of variations to choose from.

Noveske SS FTW

Correction

HARRIS GUNWORKS
7399 S. Tucson Way, Suite C-2, Centennial, CO 80112
Phn: (602)432-2871  Fax: (602)942-5327

I've always had great results from Noveske barrels. For 18" go rifle length gas.

Ha. I'm glad someones paying attention, it certainly wasn't me!
Well at least I'm right about one thing, they make quality barrels.

One other correction:
Mine is 19", .915" dia, stainless, fluted with an integrated 3 port compensator that I have had for over 13 years.

Thanks for the responses so far. Is there any advantage in terms of accuracy with either traditional or polygonal rifling?

As of now I have narrowed my choices to the three below. The noveske is in 5.56 and has polygonal rifling, the rainier is in .223 wylde with "ratchet" rifling, and I believe the Wilson combat has standard rifling a dis in 5.56. Any thoughts as to which one of these barrels you prefer and why? Any help and opinions would be appreciated as I narrow down my choices.

http://www.shopnoveske.com/collections/barrels/products/diplomat-5-56mm-barrel

http://www.rainierarms.com/rainier-arms-ultramatchtm-223-wylde-barrel-18-spr

http://shopwilsoncombat.com/Wilson-Combat-Match-Grade-Barrel-556-NATO-Recon-Tactical-18-1-8-Twist-Stainless-Fluted/productinfo/TR-556RC18F-18/