I have seen all the petals come off not only Barnes X's but some other petal-type bullets. In each instance tha animal died really, really quickly--which is why I have published statements along the line of "Who cares?" When they lose their petals it's generally because they hit some big bone (often the spine), and even if they do the front end is always expanded beyond the initial caliber anyway, so acts as as a wider "flat-point," which is very deadly itself.
One of the monometals, the G-S Custom, is even designed to lose its petals at normal velocity ranges, and kills very well indeed.
