Holdengr,
I would figure if this chamber is as nasty as you say it is you may have to tear this thing down so you can get at the chamber straight in from the rear. Brownells has chamber cleaning brushes that are on a twisted wire handle so you can bend them to go through the ejection port, but this is just for light, regular, maintainence not a seriously scabbed up chamber. You don't want the rust and crud in the action parts anyway. Get a can of Brownells Polar Active Rust Preventer, (it actually removes surface rust with a little elbow grease and steel wool) some JB bore paste, a couple of conventional chamber brushes and some wool mops that'll fit the chamber and clean like you've never cleaned before. Use the JB on the mops to polish the chamber using a variable speed drill. Once it's "clean" you'll have to test fire it and see if the brass tries sticking again. If it does you may have to solder an unfired case on an extension and using the JB on it, polish or lap that chamber till the cases stop sticking. Hopefully they will. My guess is that if this rifle is a .308 (I missed the caliber part) that maybe someone fired some corrosive primed military ammo in it and didn't clean it properly afterward. Just guessing though.AW