Jacob Snider was an American inventor, whose breech mechanism was adopted by the British for the conversion of Enfield Muzzle-Loading rifles into "Breech-Loaders", around 1868.

"Mavt" - You did a nice job of cleaning that one up and getting it functioning.

The round you fired may have been a British Prison or Riot load, (if it was military and not a 24 gauge shot-shell).

If there was a "D.C." stamp on the Left-Side of the stock-butt, it was issued to the Dominion of Canada.

I have had a worthy Snider-Enfield, since 1968. (I also have a Portuguese Cavalry Carbine, built as a breech-loader by B.S.A. in 1885. Portugal was an Ally of the British and adopted the Snider as a service arm.

The Danes and Dutch also adopted breech-loaders based on the Snider Patent.

The British Sniders are fun arms to shoot and tinker with. .577 Cartridges can be made from cut-down 24 ga. shot-shells.

After firing, the Snider is kept 'near-level' and brought to waist height.

To Extract, the hammer is cocked, the block is swung open with the side of the thumb, and the fully-opened block is pulled rearward (against spring pressure) on its axis-pin.

To Eject, the near-level rifle is rotated counter-clockwise with the thumb holding the block open. (The block is allowed to spring forward after extraction). The fired/extracted case drops to the ground by gravity from the 'upside-down' rifle. It works quickly with practice!

Kipling comically wrote about soldiers having trouble, with getting out of the habit of turning their rifles upside-down to eject, when the Martini-Henry was adopted, around 1871-72. (I don't know if this was actually true, but, why ruin a good story)!