I have not shot PPC in years (a little long in the tooth). When I competed, I alway competed in the Stock division. My sole modification was the addition of H&K grips to the pistol grip (I have rather large hands and long fingers).
Although I do not have experience w/ the Model 19, my revolver is a S&W Model 28 "Highway Patrolman". I believe that gun went out of production in the seventies. I bought mine in 1977 and I cannot imagine the number of rounds that have been pumped down that barrel. It still shoots good ten-ring groups.
I can only make two recommendations: More practice (sorry!) and take the gun to a good smith perhaps he can tune up the action.