I read a year ago I think about how the 38 special round is highly prone to over penetration. They used ballistics gelatin to prove this. Anyone know what website this came from?

Not quite sure about that but this should give you plenty of info.

http://www.brassfetcher.com

The .38 Special has a wide range of penetration depending on load and bullet type. Some are considered deep penetrators, and some are not.

From FBI tests through heavy clothng, 5 round avgs:

Win 110 +P+ SJHP 10.5 inches
Win 125 +P STHP 12.9
Rem 125 +P GS 14.5
Fed 129 +P HS 18.6
Fed 147 +P+ HS 19.5
Fed 158 +P LHP 15.5
Rem 158 +P LHP 13.8
Win 158 +P LHP 21.9

According to Speer, their 135 +P GDSB does 11 inches.

The FBI thinks the sweet spot is 12 - 18 inches. The success rate (% of rounds penetrating at least 12 inches) in their 40 shot/8 event test series for the 38 Special varies from 17.5% to 100%.

Way back in 1989 a Win 125 +P hollow point (not the Silvertip) passed through the torso of a felon before striking and killing a Philadelphia PD officer. That bullet did not expand "enough" that time, which is why it penetrated "too much" that time.

A bullet that avgs 13 inches/5 shots in gelatin may do from 10 to 17 inches in over 25 real shootings in real people.

Ya never really know what your bullet is gonna do in your bad guy.