According to the original FBI Handgun Ammunition Tests the Winchester 158 gr. JSP expanded to .418 in. and penetrated an average of 22.91 in. out of a 3" S&W Mod. 13.

Penetration (min. to max.) in each test was:

Bare Gel = 23 - 27.75 in.
Heavy Cloth =27.75 - 31 in.
Steel = 17.75 - 20 in.
Wallboard = 21.25 - 24.75
Plywood = 20.25 -23.5 in.
Auto Glass = 9.5 - 16in.
Heavy Cloth @ 20 yds. = 29.75 - 44 in.
Auto Glass @ 20 yds. = 14 - 19 in.

A lot of over penetration and not much expansion.