very nice barrels here but almost all will need to be back ordered meaning it will take a couple months to get .
http://shopwilsoncombat.com/Barrels/departments/108/
I have a Del-Ton 16" HBAR ( heavy barrel ) 1-9 twist that is very accurate . It is not chrome lined and if your going for real accuracy you may want to avoid CL .
These are not top of the line barrels but I think they're pretty good for the price . Here is a 20" HBAR 1-9 twist non chrome lined . in stock
http://www.del-ton.com/DTI_20_Barrels_p/bl1015.htm
I did not see why you want a 20" barrel . For me and my first build I'd go with a standard AR15 rifle . That way you learn about the rifle and what you really want in the platform . By the time I was totally finished with my first build . I almost had enough parts I bought and did not use to build another rifle .
Check this website daily and be ready to buy . They often have great deals but they go fast .
http://palmettostatearmory.com/
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