I tried one of the Tactical Solutions barrels. The factory barrel was much more accurate. I built another with a Butler Creek barrel that was not a good shooter either, but the Shooters Choice barrel I bought from Cabelas will shoot.
As to barrel length. Get what feels best. You will get some more speed from longer barrels, but not enough to matter. My Tactical Solutions and Shooters choice were 16", the Butler Creek at 18" felt best to me. Just wish it had shot well. I sold off both rifles with the other barrels, but kept this one.