Grand old double indeed.

Remington was making and selling muzzleloading barrels on the open market in the mid 1800's.

These generally rather heavy, octagonal barrels were rather special as their muzzles were turned & fitted for guide bullet starters, used to start conical bullets in a straight line, for improved accuracy.

They were popular for the new fairly club-organized event of sport target shooting, as far West as San Francisco - around the 1850's- on.