The method of going from rimfire to centerfire is ingenious I thought. I think it offers a solution of how to make a spare centerfire block for a Spencer without the problem of drilling a long diagonal hole. I have a Peabody in a variation of the 44-60 Peabody caliber. I started with a Peabody with a sawed of and badly rusted 450-577 barrel. I think I used a surplus rolling block barrel chambered for something like a 43 Egyptian to rebarrel the gun then chambered it for a shell that mimics the 44-60 except based on a shortened 45-70 shell and uses a 45-70 base diameter (.500" ). The original bullet diameter was .445 and the donor barrel was slightly larger (.447 I think).
Anyway, Diopter, looks like you have a nice gun and a fun one to shoot. What did you make your ammunition from?
cheers mooncoon