would like to load and shoot the spencer with handloaded rimfire ammo. its possible and would be a real challenge!

Koch mentioned in his book about hunting rifles 1891 that some Spencer were brought back by german soldiers from the french -german war of 1870/71 but I didn't find any hint that such rifles were used for hunting. iirc, there is an old story in COTW or the lyman blackpowder book about black bear hunting with a muzzle loader double rifle were one of the hunting mates had a spencer rifle.

french frank-tireurs with spencer rifles