The history of black powder rifles in the United States of America starts around the year of 1730 with the introduction of the Sidelock, Flintlock, Longrifle muzzle loading rifle "(Muzzleloaders)", of which there were approximately 7,000 manufactured.
Rifling Twist Rate, 1:60".
Then the introduction of the Sidelock, Caplock, Hawken muzzle loading rifle, in the year of 1823 of which there were approximately 300 manufactured.
Rifling Twist Rate, 1:48".
Then the introduction of the Sharps, Percussion Cap, Inline, breech loading rifle around 1848, most Sharps Inline rifles were later converted to the 45-70 black powder cartridge after its introduction around 1865. There were approximately 100,000 Sharps black powder rifles manufactured of various designs and calibers.
Rifling Twist Rate, Various; 1:42" - 1:18".
From 1865 to about 1980 black powder rifles continued to be manufactured at various levels. Then Sharps Inline design of black powder rifle re-emerged, this time it emerged as a Inline Muzzleloader and not a breech loader, of which there have been 100's of thousands manufactured as special black powder hunting seasons emerged in the United States.
Rifling Twist Rate, 1:28".
A black powder muzzle loading rifle is defined as; a shoulder fired firearm of which there are spiral grooves cut into the bore called rifling, of which is loaded with black powder and bullet from the muzzle end of the firearms barrel or muzzle-loaded.
It was at the time of the flintlock ignition system that rifling inside the barrel was now seen thus ending the era of muskets and musketeers. Rifled guns (rifles) were used to expel one projectile at a time accurately at a greater distance do to the spin imparted to the projectile, soon after the elongated bullet arrived, which greatly extended the accurate distance of a rifle.
In the 1840's percussion caps overwhelmingly replaced flint ignition systems in black powder rifles and at the same time Christian Sharps introduced an all new type of black powder rifle using percussion caps, but, the rifle loaded from the breech instead of the muzzle.
The Sharps single shot rifle design was very unique, instead of having a fixed breech plug it featured a breech block that rose and fell vertically in mortises that were milled into the receiver walls and this was done so precisely that the gases could not escape from the barrel.
The Sharps rifle fired a paper black powder cartridge, once the cartridge was loaded into the breech the lever attached to the breech block was drawn up, this allowed the breech block to rise and shear off the end of the paper cartridge exposing the powder charge, the rifle was then capped with a percussion cap and fired. These first rifles were later converted to metallic black powder cartridges.
Inline Rifle Design:
The Christian Sharps rifle design of the first breech loading, percussion cap, black powder rifle, was also the first true black powder rifle Inline ignition system as well. Tony Knight of Knight rifles reintroduced this idea well over 100 years later to which he had received much praise for his design. To Mr. Knight's credit he does admit he only improved on an old black powder rifle design.
Note: Sharps rifles were well known for their long distance accuracy. Enough so that military versions of Sharps rifles issued to their users, those issued the Sharps rifle were known as Sharps shooters, later condensed to "sharpshooters".