As above, you need either .32 S&W or, preferably, .32 S&W Long cartridges. Both sizes are still manufactured, but many retailers do not stock either as they are not too popular these days. Gun shows are one source, and some dealers may special order them for you if they do not have them in stock. The .32 S&W and the .32 S&W Long (or .32 Long) cartridges dimensionally differ only in case length. The .32 S&W is used mainly in the old top break pistols made by various manufacturers back in the black powder days. The longer .32 S&W Long cartridge is made for solid frame revolvers, and cannot be used in the old top break revolvers. I hesitate to suggest this, and don't recommend it, but .32 ACP (.32 Auto) cartridges can be used in revolvers chambered for the .32 S&W Long as a last resort. There are several disadvantages to doing so, and this is why I say to use .32 ACP only as a "last resort."