Listen to skeetx. The 3" shotshell wasnt introduced until 1923 and in only some heavily costucted heavy waterfowl guns. Odds are your shotgun has 2 5/8" chambers. The RST loads are about perfect for that age of shotgun.
Again this is an old cartridge for small game, very good for turkey with the original cast bullet loads. While 3031 is considered a fast powder for modern deer cartridges it is again too slow the old 25-25.
Reloading dies can be found used on ebay but it might be a long wait, for new i would look to C&H4d, great company to deal with for the old ones. Buffalo arms usually has C&H dies for most older cartridges. COTW might have some data for reloading.
Remember you are dealing with a firearm that is over 100 years old, treat it kindly .
