How about something like this— http://www.doubletapammo.net/index.p...product_id=555
Assuming that the advertised velocity of 800 fps* out of a 4'' barrel holds for one's own revolver, the DT hardcast wadcutter (21BHN) should offer penetration between 18 and 22 inches according to the various predictive models.
D = 0.3575'', M = 148 gr., V = 800 fps
Q-model = 18.31 inches
mTHOR model = 20.52 inches
MacPherson model = 21.99 inches
*If the .38 Special 148-grain hardcast wadcutter has to pass through a barrier before striking a human body, there should be a commensurate loss of penetration depth in accordance with the velocity lost due to the barrier encountered.