anyone know of a good reliable local gunsmith to thread a AR barrel for a flash supressor?  portland area or 50 mile radius would be good. thanks

Revelation Arms in Aloha.  I've never had work done by Roger, but many of the people I shoot with have and recommend him highly.
Revelation Arms

Another alternative is to rent one of the threading kits and do it yourself.  I rented one for under $20.  It only takes 10 minutes to therad a barrel.
Barrel Threading Kit Rental


If you require your barrel to be threaded on a lathe, expect to pay about $100.  I went with the TAT threading guide and die for $20.