IMHO, one does not really need to practice single action shots out of a snubby (what for?). You can hit things with it to 50 yards in double action. I tried my 442 against a steel ram @ 100 yards last Sunday and I was consistently hitting 3 of 5 with a best of 4 of 5 holding on the "spine".
So IMHO, since the hammer is not needed, the 340 is better suited to snubby applications.