I just found some useful .380/P3AT test results at www.goldenloki.com . Too bad they didn't include heavy cloth in their testing.

I think the Fiocchi Extrema is worthy of note. My hunch is that the bullet expanded, but the petals were folded back to the front when it tumbled backwards. I've seen that happen before. Had it not expanded, my hunch is that it would have penetrated deeper.