Thanks BobM
Two FLints, the Spencer Sporting does not seem to be an European alteration. As far as I know, it is a civilian model that was bought with left-over parts at the Spencer factory. The 56-46 caliber is an original Spencer caliber. At the time it was a rimfire cartridge, like the 56-40 and 56-56.
I will check at Buffalo Arms , and see if the brass they sell would be OK for this rifle, since the exact caliber of this particular rifle seems to be .457, so hopefully is their brass OK for .457 bullets. Maybe a 45-70, 405 gr lead bullet will do... Well, I'm pretty excited and hope my friend will buy the rifle (I have not the money for it right now, anyway). Thanks again BobM for the addresses !
The rifle has a tang sight, that seems to be all original given to the pictures in Roy Marcot's book (square and not adjustable).
I don't know why, but I've seldom seen one of the more classic models (1860 or 1865) so far. My guns are a New Model carbine and a Model 1867 rifle (one of the 1st produced, it has still the "1865" markings on the barrel). These are not the more common among Spencers... And now this Sporting rifle !
I must call back my friend now.
Thanks again folks !!!
"Frenchman" Clyde