There are two extractor types, the 1st generation had problems, those barrels could be either twist rate, the late extractor type would very likely be 1:9", but I don't know when they developed the late style. My .500 S&W barrel has the late style extractor. The only way to know for sure is to check the twist rate, procedure is in the FAQs under the twist rate info. Pics of underlugs are in the FAQs also as well as a link to a gen 2 extractor in pieces.
Tim