All I knew about Sig before buying my first Sig 1911 was that they had a reputation for good triggers. I bought my first Sig because I could not find a VBob, much less afford one, and I looked at the Sig Fastback Carry as sort of a "Poor Man's VBob."
I was so impressed, I turned around and bought another Sig shortly thereafter (the one in my Signature).
So now, I have four 1911s with extractors (One DW, two Sigs, and one Mimber 22 Conversion slide) and the DW and Sigs just work. The Mimber 22 slide sometimes will leave a round in the chamber after firing. At the time I got it, I was not aware of the history of 1911 external extractors, and I studied it carefully to determine why it was slipping off of the rim. After careful analysis, I determined that the extractor was simply too short.
I had previous experience with short extractor problems - a Walther P-38 - that exhibited similar behavior to the Mimber 22 slide. What happens is that when you have a case that is difficult to extract, the short extractor quickly loses its grip because the angle of engagement with the rim changes very rapidly if the extractor swivels out slightly. On a long extractor, the angle doesn't change as much when the extractor swivels out a little. On an internal extractor, the extractor would have to bend for the angle to change because it doesn't swivel out like an external extractor.
Here is a graphic to illustrate:
I'm not so enamored of the internal extractors after going through hell with my Colt Series 80 (that gun wrote the book on 1911 malfunctions). And my Rock has some extractor issues of it's own (at least that's what people say causes it to eject forward)
