green mountain now has a number of ar-15/m16 barrels back in stock-- 16" 14.5" and a2 20"s including the excellent 1-8" a2 with hard chrome lining--
they also have a 10.5" 9mm in nitride finish which i think would give a perfect dwell time in a 9mm SBR--
and green mountain has a new 7.62x39 ar-15 m4 barrel with chrome lining--
none of GMs barrels are "budget priced" --they are very high quality and made to very strict standards.
PSA also has the stripped ar uppers back on sale for $39.99