The only barrier test info I have left at hand for .38 Spl is from something Winchester provided from 2002. It lists various loads fired from a S&W M60 2" and includes their X38SPD 158gr LHP +P.
According to their factory testing in the Autoglass barrier test it averaged penetration of the gel behind the glass barrier of 7.1"; exp. 0.63" & retained 83% of its original weight (recovered at 131gr). No images were provided. That level of penetration was at the upper range of the various loads they tested from within their product line at that time. Last I heard the Winchester LHP +P offering still used a harder lead than the Remington load I generally use, and I can't find any of the results from some previous state-sponsored testing I was told about involving the Rem load in 2" snub revolvers.
Now, I've never been particularly concerned over how my defensive handguns defeated automotive windshield glass ( or steel). I've seen and learned of variable results over the years across the wide range of calibers often encountered in LE work. I do tend to like heavier bullets if the situation and overall circumstances permit it, though.
I've recently learned of a large metro agency who is reportedly planning to issue S&W J-frames as secondary weapons, and after much testing the ammunition choice is likely going to be standard target wadcutters, although the Speer 135gr GDHP +P did very well in ballistic testing (no surprise).
Why the standard wadcutter? Well, apparently the consistently better accuracy demonstrated by the average shooters was significantly better than when the harder kicking +P HP load was used. Again, not really a surprise. The performance capabilities of the WC load is apparently within the range of what the agency considers appropriate for their officers' usage as a secondary weapon caliber/load in the circumstances they anticipate them encountering.
I'd be a bit surprised if they were particularly worried about autoglass barrier situations while they were developing the concept of issuing J-frames as secondary weapons. Haven't asked them, though. Just a guess.
The cutting/crush characteristics of the WC bullet have been muchly discussed and debated. I remember hearing of the concern of some folks upon occasion regarding potential penetration of low-velocity WC's when bony structures & intervening limbs, and some really heavy clothing (layered leather vests, jackets & denim, etc.) may be involved. Dunno the 'answer' to that consideration, although personally I'd still rather have accurately placed hits than misses caused by flinching due to recoil greater than the shooter of the moment could tolerate and handle. Pick your poison, I suppose.
I've used a wide variety of .38 Spl loads over the years. Lots of them. Nowadays I generally use either the Rem 158gr LHP +P or the Speer 135gr GDHP +P in the J-frames I carry which are rated for +P usage (either full-time or at least for limited usage). I use a couple of different standard pressure loads in an older style M37 Airweight.
The felt recoil of the standard pressure 158gr LSWC and 148gr WC do allow for some great controllability and fast follow-up shots, though. I've certainly enjoyed some accurate shooting with 2" 5-shot wheelguns over the years using both loads.
Their time may be coming back around again ...
Stay tuned.