Actually the Browning HighWall in .45-70 Owners Manual reads as:
"The Model of 1885 BPCR is a special version of the famous Single Shot rifle designed for in the BPCR metallic silhouette competitions. It is designed primarily to shoot black powder or Pyrex cartridges in one of the two calibers (although shooting smokeless loads in the .45-70 Govt. version is permissible)."

I have heard the smaller caliber was never listed per Saami specs and that is why they do not list both of the calibers for smokeless.

Ranch13, this raises the question...Which part of my shooting my Browning High Wall requires I check my homeowners insurance?