Vega,
Limpwristing is one cause of a smokestack-type jam. As Jim notes, they can also be caused by the extractor, ejector, or a combination of the two.
Ironbar,
Yep, the cases invariably end up ejected on mine, as well, but the case mouths are still mangled. It's a simple case of the case getting caught and mangled, but still escaping.
Jim,
Can't say I disagree with you, but I do like the added benefit that a lowered and flared port gives. With such a modification, smokestack jams under any condition are virtually eliminated.
Oh, and a better analogy would be it's not unlike reshaping the door strike or jamb so that the door doesn't stick.
