First task was to slug the bore so I could order a mould and sizer die.
The Burnside contract Spencers have 3-groove rifling, which makes it tricky to measure the groove diameter because the grooves are diametrically opposite the lands. Not knowing a better way I drilled a half inch hole in a piece of rod and bored it out in small increments until the slug was a tight fit, then measured the hole with a bore mike.

There must be a better way?
Last week I was visiting our manufacturing plant in New York so I took the slug along and put it up on an optical comparator. My crude method said the bore was 0.515 and the comparator said it was 0.5153.
Next up was fitting the center-fire upper breech block. S&S Firearms claim their block will drop into 95% of Spencers with no alteration, but my gun was clearly in the other 5%. The block dropped in ok but the action would not close on it. Spencer's design is simple but it is very picky about fits and tolerances - it took me a lot of patience, a Dremel and a few curses to get to where the action cycled as smoothly as my old Winchester '73.

Sure, it drops in, but will it work?
I had heard that Spencers were ultra-sensitive to cartridge length and bullet ogive shape and I was about to find out. buffalo Arms told me that they were no longer able to export brass so their ready-made 56-50 brass was a non-starter. I scratched around to find a UK dealer with 50-70 Govt brass and finally found 50. I roughly cut them down with my Harbor Freight mini chop saw and trim to final length of 1.15in on a Forster trimmer. Inside reaming to 0.515in and a touch off the rim on the lathe and it's done.

My setup for making 56-50 brass from 50-70
I made up several sets of dummy cartridges in different lengths until I found what fed easily though the action. For my gun the optimum COL is 1.560in with the 375 grain bullet from a Buffalo Arms mould.

My feed-trial dummy shells,50-70 and 56-50 brass,375 grain bullets
Finally, something of major importance......

To avoid blowing your face off, replace the original round nose magazine
follower by a flat or cupped one.
Other than a light wipe with bronze wool and oil I have not touched the outside of the gun. It took 144 years to acquire that "experience" and I'm not about to polish it away.

Ready for the range
Just one more obstacle to surmount before I can get to the range. I live in the UK and hold the gun without a licence as an antique,obsolete caliber gun. As I now want to shoot it I have to apply to have it added to my firearms licence. I don't anticpate any problems but the wheels of officialdom don't turn very fast. While I am waiting I can cast up different hardness bullets and trim the rest of my cases but I can't actaully load any ammunition without risking prosecution.
Perry Owens