Hey photoman nice groups. I know that Magnum Research uses a BENZ chamber in their graphite barreled 22's. It is extremely tight for an auto loader and you got lucky going that many rounds. I had the same issues and found cleaning the barrel every 300 to 500 shots depending on ammo cured the problem. I also tried the Volquartsen extractor and after 5,000 rounds it ruined my barrel. It actually cut the extractor slot deeper. It was simply to sharp and too hard. Forunately Magnum replaced the barrel for me. Keep up the good work, love the pictures.

Jackpinejim