I have been following this topic at tacticalforums.com for a number of years and am in regular contact with Dr. Gary Roberts, who is arguably one of the world leaders in the testing of ammo for defense, service, & military applications. Dr. Roberts' testing reveals that the 158 gr SWCHP +P load that so many of us have carried for years generally fails the 4-layer denim test (i.e., it does not expand) when fired out of snub 38's. It performs much more reliably out of 4" and 6" barrels, so it's a suitable load in such guns, but it is not recommended for snubs.
Based on Doc Roberts' tests, I have changed my J-frame carry loads one or both of the following: 148 gr standard pressure wadcutters, or Speer 135 gr +P JHP. The 148 gr wadcutter is very mild in terms of recoil, and cuts a very nice full-diameter permanent wound cavity. Note that this is NOT the mythological hollow-base-wadcutter-loaded-backwards load. This load penetrates 12+ inches, even thru denim. The 135 gr JHP load expands reliably and penetrates 12+ inches. I usually go with the wadcutters in in the gun, with a Bianchi Speed Strip holding 6 of the Speer JHP's for reloads.
I have 3 J-frames which I carry regularly, usually in a pocket holster (I like the cheap Uncle Mike's fabric holster better than any of the expensive molded leather and kydex pocket holsters I've used). Two are S&W M442's, and the third is a M640. On the 442's I have Eagle Secret Service grips, and on the M640 I have an Uncle Mike's boot grip (the long one that S&W ships the guns with). I have found that I can shoot 30 to 40 rounds of the Speer 135 gr +P load in the 442's without pain, with good accuracy. In the 640 I can shoot 60+ rounds and still feel quite comfortable. I believe the rubber boot grips really make the J-frames more shootable, but they tend to hang up in a pocket. But there is a solution to this in the offing.
At this point I am getting ready to change the grips on my 442's to the Crimson Trace LG-405 grip. I have tested this grip/gun combination and it is worth every penny. This grip is molded of a less 'sticky' rubber compound, yet has a nice backstrap cushion. The laser dot really enhances getting back on target quickly in rapid-fire mode. Also, I found I can make longer shots much more reliably.