maybe only in tv or the movies, i have seen military and police use rubber bullets to stun the person. which it is more practice than shoot in the arm and the leg to slow down. these rubber bullets come out of shotgun for more punch to it.
Over here they are called "Baton Rounds". British police and army used them in Northern Ireland from the 1960's. They're nothing new.
They also caused some fatalities, for example, by hitting the area of soft organs and causing massive internal bleeding of striking the target in the head and causing severe injuries.
As for the practice of studying the ballistics of various rounds, using pig carcasses and gels, they don't fully simulate the effect of a round on a human body. Sure, they can tell what effect a round of this or that calibre might have on flesh, if flesh was all they hit, but any round that penetrates a human body may very possibly deflect off a bone, such as a rib or hip and it's path through the body significantly altered.
Also, deflecting off a bone may make the round tumble end over end. It would lose some force in this way but would do considerably more damage as it passed through the body.
All of these factors, and more besides, make the forecasting or predicting of how fatal a particular round may be, or whether certain rounds could be used as "stop" a target rather than kill him / her outright almost impossible to ascertain. Probabilities can be estimated, but not guaranteed.
The only thing we can say for certain is that all firearms have the potential to kill