Cap N Ball...
Please don't use that cherished family heirloom for self defense. Use a modern firearm instead and if you must buy one of those used S&W Model 10s for less than $150, do so. Here's why:
Guns used in shootings are seized in evidence. Typically the cop in the evidence room isn't a gun buff and to him it's just another gun. Toss it goes onto the shelf. While it sits there, since it hasn't been cleaned or oiled, it begins to rust. By the time the DA determines that it's a good shoot and no charges will be filed, your once cherished heirloom will be scratched from rough handling, nicked from being tossed onto the shelf (with possibly some chips of wood being missing), rusted from no hygroscopic action of the black powder residue, lack of preservatives and handling by humans with "acid" hands. So, put the gun aside and let a more modern gun do the work. Please, for your children's children, do it.