It would have been expensive to re-tool to allow a longer cylinder & frame to accommodate it, instead the military switched to .45 S&W cartridges that could be used in either S&W or Colt. Apparently the ease/speed of reloading didn't get enough pluses to hold interest, they were phased out & the cavalry kept the more rugged Colt SAA. Cavalry handguns have always been backup weapons & they only carried 20 rounds of ammo so faster reloads weren't a big point. OTOH border outlaws like Jesse James loved them.