The Model 29-2 was manufactured in three barrel lengths; 4", 6 1/2", and 8 3/8". I have never in my life seen a 3" or 3 1/2"-barrelled 29-2 that wasn't a custom job. There was a variant of the 629 made with that barrel, one of which was prominently used by Steven Berkoff in the movie "Beverly...
I'm a disciple of the late great Bill Jordan, one of the greatest wheelgun man who ever lived. Consequently, I have always been an advocate of the double-action revolver for defense. Semiautos are fine, and it's really all a matter of what you're most comfortable with. I have a Sig-Sauer P226...