7 Claude-Étienne Minié 7yards (274 metres) balls from muzzle-loaders lost most
of their lethality. These ballistic shortcomings were a
product of the requirement that the projectile, in order
to be quickly rammed from muzzle to breech, had to fit
loosely in the barrel. When discharged, it wobbled down
the barrel, contributing to erratic flight after it left the
muzzle. Rifled barrels, in which spiral grooves were cut into
the bore, were known to improve accuracy by imparting a
gyroscopic spin to the projectile, but reloading rifled
weapons was slowed because the lead ball had to be driven
into the barrel’s rifling. In 1826 Henri-Gustave Delvigne
of France, seeking a means of expanding the projectile
without making it difficult to ram home, created a narrow
powder chamber at the breech end of the barrel against
which a loosely fitting lead ball came to rest. Ramrod
blows expanded the soft lead at the mouth of the chamber
so that, when fired, the bullet fit the rifling tightly. In 1844
another French officer, Louis-Étienne de Thouvenin,
introduced yet a better method for expanding bullets. His
carabine à tige embodied a post or pillar (tige) at the breech
against which the bullet was expanded.
These rifles worked better than earlier types, but
their deformed balls flew with reduced accuracy. Minié,
inspired by Delvigne’s later work with cylindrical bullets,
designed longer, smaller-diameter projectiles, which,
having the same weight as larger round balls, possessed
greater cross-sectional density and therefore retained
their velocity better. In order to combat the tendency of
muzzle-loading rifles to become difficult to load as gun-
powder residue collected in the barrels, Minié suggested
a major simplification—eliminating the pillar of
Thouvenin’s weapons and employing in its place a hollow-
based bullet with an iron expander plug that caused the
projectile to engage the rifling when the weapon was fired.