Could not take it anymore trying to remember and went and dug mine out. Controlled feed bolts have an open area usually flush to bolt face at 6 o'clock allowing cartridge base to slide up face and slide under the extractor. Single feeding requires the extractor to force itself around rim going into battery putting a lot of stress/bend at the thin spot just forward of collar. Probably many a Mauser and 03 have been massaged to allow (get away with) this but at the cost of claw engagement on rim. Push feed usually has a full circumference rim with a spring loaded extractor allowing single feed with no harm. Looking at this bolt and the small rim (mine has been opened up for 45 Auto) and the tenderness of these extractors and being made of unobtainium I will not be single feeding. This design to me appears to be a controlled feed only even having the small rim. The designers probably felt that with extractor at 12 o'clock the rim was needed at 6 for extraction and control of round. With rim being small enough still allowing controlled feed design as cartridge is pushed forward from magazine angling up under extractor and then captured by bolt face for alignment with chamber.