Check out this thread...
http://www.10-8forums.com/ubbthreads...r=51276&page=1
It looks like Type II extraction issue. My guess is that you have improper extractor tension. You can test that easily. Follow this link:
http://blog.wilsoncombat.com/uncateg...-on-your-1911/
If you cannot get the proper tension buy a new extractor and tension it and then test. A good way to test the proper tension on an extractor is to load 1 round into the chamber from the magazine. Drop the mag and then fire the gun with no mag inserted. Mags can help mask extractor issue because it will help support the case during extraction and ejection. If the gun can fire 7 to 8 times this way and if you get proper 2 to 5 o'clock extraction you should be good to go.
All that said take my free advice with a grain of salt. I shoot 1911s and love them to death but I am not in anyway shape or form a gunsmith or 1911 tinkering expert. Maybe if you are lucky 1911tuner will stop by and offer some thoughts.