Keep in mind that most of the better reports on full wadcutter .38 specials involve bullets traveling around 800 fps and not the 600 fps the OP preferred. The late Stephen Camp firmly believed that the light target wadcutters were not the defensive round some believed they were -- http://www.hipowersandhandguns.com/Feedingthe38Snub.htm
. Now, if you do get a full wadcutter traveling at 800 fps (especially harder lead), then you've got a decent defense load. Of course, to accomplish that would probably cause more recoil than the Speer 135 gr. Gold Dots for short barreled guns which is about the best load for a .38 snubby IMO.