RST 2.5-inch 20 gauge


Welcome! RST does sell low pressure shells for short chambered vintage guns, but their inventory is limited and only intermittently available. Today they do list as available 20 gauge 2.5 inch shells, 3/4 ounces and only #9 shot. Their shells sell out pretty quickly and if you want to buy them you need to check the website frequently, or I think they may be willing to notify you of availability if you contact them.
I have been handloading for a couple of short chambered English guns I have (16 and 20 gauge) and find it enjoyable. If you are interested in going the handloading route I would be happy to share what I have learned about it.
Many others on this site are more knowledgeable than I about the guns you have acquired. The LC Smith 20 gauge is certainly a great start.