Improvements in engineering and technology during the industrial revolution would bring about the greatest changes in artillery for 300 years, one of which was rifling. Steel became commercially available in the 1850s - 1860s and a steel tube could have a number of spiral grooves running down its length, called rifling. When used in a barrel, these grooves would spin the projectile, markedly increasing its range and accuracy, making smooth-bore guns obsolete. Some large smooth-bore guns were ground out and had a rifled tube inserted , but new ones, were purpose-built.
As the guns themselves changed dramatically, so did the ammunition they fired. Round shot gave way to longer, more aerodynamic shells. To engage the rifling, to spin the shell and make it more accurate, early shells were fitted with studs. These shells with studs were muzzle loaded.