With most 380 ammo you have JHP which fails to penetrate past 10" or FMJ which zips right through 19" of ordnance gel.
I think 380 bullet design is starting to improve the way 9mm bullet design did. It is possible to get 12+ inches of penetration thru 4 layers of denim from the Hornady XTP with
some expansion:
http://www.youtube.com/watch?v=wOwCXXpEP50Oddly enough, Hornady's loading of their XTP doesn't do as well as Precision One's loading of the bullet.