Kart 22 LR conversion chamber repair?

I have had a Kart 22LR conversion for about 5 years now, and have never been able to get it to run more than 4 rnds in a row. Always has problems with a failure to extract. Have 1 original mag, 2 advantage arms and one GSG mag. I fired a high velocity rnd in it this weekend, and had to pry the brass out with a tiny screwdriver. The expanded brass showed grooves in the chamber. The last Smith I took it too used what he called a lead reamer to "clean" the chamber. The gun had more extraction problems after that. I would like to just send the whole thing to an expert and are what.the heck is wrong. Anyone know who is actually familiar with them enough to diagnose and fix?
David

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