I had a 629-4 with a 6" barrel (short underlug) and knocked the cylinder out of line by shooting about 100 300gr Garrett rounds through it. This was back in 1999. Smith fixed it on warranty but cautioned me that the gun is designed for SAAMI 250gr loads, maximum - but that I could shoot maybe 30 300gr rounds per year to stay practiced and sighted in. I went to the Redhawk instead. You might contact Smith. They were very willing to discuss the gun's limitations with me. There was a change called the "Endurance Package" for the 629 but I don't know which guns have it. One of these days I'm going to get another one...maybe a 4" for the trail. I really like the 629. adk