How about scaling the existing 45 caliber collar button mold to cast a .408 collar button for the 40-60, 40-65, 40-78, etc. This should be real fun in the Uberti 1876 clones.
I just read the article about NOE’s 45 collar button mold (2017 Gun Digest). The article again wetted my appetite for a 40 caliber version (casting at .408) for my 40-65 and 40-60 rifles. Just copy the current one with reduced diameter. There must be someone out there with one of these rifles.