Beautiful!
I made mine on the .357 full size Blackhawk frame. It has the tight chambers, throats and b/c gap that can take advantage of the Buckeye Sports (responsible for the Ruger Buckeye 38-40/10MM & 32-20/32 Mag limited editions) 38-40 Magnum 'Ruger Only' loads.
.38-40 Magnums and the guns for them by LEE MARTIN
http://www.singleactions.com/files/3840WinchesterArticle.pdf