Any one of a number of things could happen. The bullet could expand too much and not penetrate enough, it could break apart and have shallow penetration, or more than likely, it will penetrate well enough to get the job done.

The .38 +P short barrel loads are pretty good performers out of 2" snubbies. Auto pistols are a different story. For one thing the pressure is a lot higher on a 9mm than it is on a .38. The velocity is different too.

http://www.ar15.com/forums/topic.html?b=5&f=20&t=85661