You didn't tell us the specific model, but I'm going to assume it's a Chiefs Special or similar (Steel frame as well). From what I've read in several sources, the 5 shot J-Frames can handle limited use of +P ammo. The bolt cuts are between the chambers, therefore, the cylinder will have plenty of strength. John Taffin recently wrote a couple of articles for American Handgunner (I think, it could have been Guns Magazine) discussing J-Frames and snubnosed handguns. He talks about the strenth issue in one of those articles.
From his online article discussing J-Frames (http://www.sixguns.com/range/jframes.htm):
" Anyone who has read many of my articles know that my usual forte is the big and bold, the Magnum and beyond sixguns and the big bore semi-automatics. But I have definitely found a place in my collection for this little five-shooter. A Plus P five shooter I might add as Smith & Wesson does classify this little .38 as one that is able to handle the hotter loads. No little strength certainly comes from the fact that the Model 60 carries a full length cylinder with very little barrel protruding through the frame unsupported. The cylinder also, being a five shot, has the bolt cuts between chambers rather than under them."
Elmer Keith is another who has discussed the strength of these guns. He too came to the conclusion that these are sturdy guns.
I have an early 60s vintage Model 36 that I have shot +P loads in order to determine POI (Federal 158gr LSWCHP shoots to point of aim at 15yds in my gun). My practice loads are the same bullet loaded down to standard pressure levels.
Chris