Having just entered the world of revolvers with my own snub nose .38, a S&W airweight 637, I found this article very eye opening.
But I think many of you would do well to read the full article and see the videos, especially those that are saying 'load +P rounds and you'll be all good', as that is exactly what the original article is about.
Modern .38 spl SD ammo such as Speer Gold Dot 125gr +P and 135gr +P, Winchester PDX1 130gr +P failed to expand when cold out of a 2" (or less) barrel. Unfortunately, the article fails to mention what 'cold' is exactly (other than a mention of putting the gun and ammo in a ziplock bag surrounded by ice water).
The article goes on to show that warmer temperatures have positive (but marginal) effects, and that the same ammo fired from longer barrels (4" in his example) perform as intended.
I think I will be picking up a box of Buffalo Bore 158 gr LSWCHP +P, which appear to work well from short barrels.
ETA:
I've made reference to this once before on this site, but here is a link regarding a self defense shooting that happened in Missouri a few years back.
http://www.ar15.com/forums/t_1_5/988015_My_CCW_Shooting_AAR__Now_with_More_Graphic_Pics_on_pg_29_and_30.html&page=29
The victim took 4 out of 5 rounds from a snub nose .38 (a S&W 36 I believe) at point-blank to across-the-room distances - one in each hand, one in his shoulder which exited his arm pit, and one grazed his stomach. He survived. Rounds used out of the .38 were Speer +P (no other info about weight, grains, bullet type that I recall). You can see more pics at that link I posted.
as you can see from this pic, there was no expansion.