Just to add to what Guy has said. In the Portland area we have two ranges that hold competitions,
Tri County Gun Club, TCGC.org, We hold a Ture 600 yard benchrest match about once a quarter. We will have one the 17th of Jan, and then 21st of March.
In Feb TCGC wil hold a tactical "sniper" match, but I think they only allow 30-06 power and below.
Second club is Douglas Ridge Gun Club, Douglas Ridge Rifle Club
They have a three shooters over there on the US F-class team. I know they are holding a tactical rifle match and f-class matches. They're the only range in the Metro area that has a 1000 yrd range.
I know its a drive, but every 3 rd sat at TCGC we have a 600 yrd shoot. Not a real competition, just some guys shooting and having a good time. I would say the Saturdays we are holding a match, if your not shooting in the BR match then, its not a good weekend to show up. Sorry, but we do not hold a "stock" rifle class. Just Heavy and Light gun.
If you have any questions, give me a PM and I can give you my cell number.