Installing a barrel on a S&W revolver generally can be done without a lathe, but by the time you buy (or build) the proper tools and fixtures you will have spent more than a good gunsmith would charge to do it for you. And if the barrel does need to be altered to fit, (for instance, if it is too long for the cylinder to close), then you will need a lathe, tooling, and the knowledge of how to use it.