FYI ... I'm reading info. on the 7.62x39 page on FB about some bad extractors. I recently bought a "7.62x39 Super Duty Extractor" from http://www.shop.ar15hardware.com , made by Alpha Sooting Sports, Item #SD762EX @ $21.95 and it appears to be nickel boron in finish.
Just thought Id put that on here in case you and/or anyone else has that problem. I haven't had to use it yet so I cannot verify how good it is but at least it's offered as such.