Re: AR-10 Barrell
There are numerous options for quality Armalite-pattern barrels. It more or less comes down to several issues as to which is best for you based on: 1) price; 2) how long you want to wait; 3) how much work you want to go through on the end (i.e. - do you want a "drop in" barrel that you can order/install yourself or do you want a blank to have somebody like GAP, etc. install the extension/chamber/fit/etc.).
I'd personally stick to something around the 18-20" length MAX (closer to 18" for a barrel you are going to be running/gunning with to save length/weight/etc.).
Check out the following as a start (in no particular order):
1) Rainier Arms UltraMatch Armalite pattern;
2) Rock Creek 5R;
3) Krieger;
4) Bartlein.
There are also the Armalite barrels direct from the factory which include the match barrels they use for the AR-10T rifles/carbines, as well as the NM model, which are good options. Noveske also has excellent, match-quality Armalite pattern barrels!