looks like the remains of a Spencer

Has the tube plug in, I soaked it with PB Blaster to see if it would loosen up.

My great-grandfather bought one (.56-50) and 3 bushels of cartridges for less than $5 when he came to this country in 1880.  He used it in his slaughterhouse.  It stayed in use until 1954, when my grandfather retired from the custom butchering business.  If it was cleaned, it was not often.  I was a freshman in high school when my grandfather sold the remaining cartridges (one bushel of them) for $100, which was about 5 % of the price of a new Chevy.

My uncle took the Spencer into the wilds of the UP.  We never saw it again.

ABSOLUTLY CORRECT George  I KNEW that, but I'm recovering from some minor surgery so we can blame it on the meds   Had some interesting typos too. 

   I must have been thinking of the fact that it and the Henry were the two that were successful deployed in  any quantity during the C.W. and the Spencer was probably the one with the greatest numbers.    I suspect it was the quick reload magazine tube.   but it never took off much after the war.-----and thinking about why.

were any of the larger bore single shot chambered for the spencer round?

I suspect it was the quick reload magazine tube.

While the Henry held more rounds and was quicker to cycle, the Spencer, especially with a box full of Blakesley reloaders, may very likely have been technically quicker to reload.  However, most authorities claim the Henry's real performance bugaboo was the ease with which its open, under-barrel magazine could become dirt-clogged, bent, or otherwise if only temporarily inoperative.  Still, it was the Henry that earned the name "That damned Yankee rifle ...".  And of course it was also the Henry that provided the initial basis for the Winchester company.

If anyone has ever noticed the resemblance between the Spencer's lock and the Peabody's ....

I've never examined a Providence hammer-action Peabody, but I can opine both from reading and direct comparison that at least several lock parts were either subcontracted from Sharps or supplied by a subcontractor that Sharps and Spencer (and maybe Peabody?) shared.

Bill Lawrence