Look for the Johnny's Reloading Bench Youtube video about Grendel extractors. There's a significant number of Grendel extractors out there which lock up cases in the rim groove as they exit the bolt. His fix is valid and it worked for me.
Stronger extractor springs and o-rings cause excessive extractor force which shaves brass off your cases and the shavings are left on the bolt face to cause other problems.
Stovepipes can be caused by the action cycling too fast (though a grabby extractor can do it too).
Regardless, the soot indicates pressure leakage that will not be conducive to the most consistent groups. I use blue Loctite to seal my gas blocks and tubes, and when I get around to it I'll buy some high temperature blue LT for that purpose. I also have a short length of vacuum hose that I push onto the end of my gas tube afterwards and blow through it to make certain that I didn't block off the gas channel with LT.
Stronger extractor springs and o-rings cause excessive extractor force which shaves brass off your cases and the shavings are left on the bolt face to cause other problems.
Stovepipes can be caused by the action cycling too fast (though a grabby extractor can do it too).
Regardless, the soot indicates pressure leakage that will not be conducive to the most consistent groups. I use blue Loctite to seal my gas blocks and tubes, and when I get around to it I'll buy some high temperature blue LT for that purpose. I also have a short length of vacuum hose that I push onto the end of my gas tube afterwards and blow through it to make certain that I didn't block off the gas channel with LT.