I got rid of all my H&K91s, PSG1, and Springfield copy. I had that problem with my 91. It turned out that the chamber was tight and even the fluting wouldn't allow proper extraction. I finally ended up cycling the +p rounds (designed for bolt guns). Then I hear horrer stories about extractors and H&Ks that only liked certain rounds. They all destroy brass..
Yeah, you could operate on it and chance ruining a "gun worth thousands of dollars". If it isn't reliable, it isn't worth ****. Why own it?
I agree with AR15_Fanatic, pound for pound, a good Bushmaster M4 is hard to beat.