I looked in my records and found expansion and penetration data for the Winchester .357 Magnum 145 grain STHP load# X357SHP. This data is from Winchester's 2009 LE Duty Handgun Barrier Test Data. The firearm used was a 4" S&W Model 686.
Bare gelatin
Expansion .55 inches
Penetration 15.3 inches
Heavy clothing
Expansion .58 inches
Penetration 16.4 inches