Encyclopedia · Projectiles and ammunition

Rotating and expanding bands

A rotating or expanding band is a ring of soft metal around a rifled projectile that is forced into the rifling on firing, spinning the projectile and sealing the bore against escaping gas.

Also known as: driving band, expanding band.

FunctionTakes the rifling and seals the bore
MaterialSoft metal, usually lead or copper
ActionPropellant pressure expands the band into the grooves

Taking the rifling

In many rifled systems the projectile was slightly smaller than the bore and carried a band or coating of soft metal. When the charge fired, the pressure upset the soft metal outward into the rifle grooves, so the projectile was both sealed against gas escape and turned by the rifling to spin in flight.

Bands and coatings of lead and copper were central to Civil War rifled projectiles, and the way a band was formed and attached, whether a base cup, a raised ring, or a full coating, distinguishes one inventor's system from another.

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