The US military reworked a few of these for Cavalry use back in the day.
They ended up as .50-70s, mag held only 4 rounds.
I have seen and handled 2 of them.
BTW, Spencers were used by the Manitoba Prison Service right up into the 1920s. They were marked MPS. Must be the very last Gummint use of Spencers on record. Saw 2 of those, too, many years ago, didn't have the $35 to buy one.
Hope this helps.
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