Have you looked are replacing the 30/30 barrel with a 357 magnum? The 38/357 brass is easy to come by and the 357 will do anything the 30/30 will, out to 250 yards, using less powder. Casting bullets for them is as easy as it can be and you can make very quite loads with a lot more punch than the .22 cals.

Enjoy the search and good luck!

“My horn is full and my pouch is stocked with ball and patch. There is a new, sharp flint in my lock and my rifle and I are ready. It is sighted true and my eyes can still aim.”
Kaywoodie