Tapering (firearms)

In firearms, tapering refers to components that narrow down like a cone does, hence the name taper.

Barrels

In barrels, this centralises mass to the operator, not only to reduce perceived weight due to center of mass, but also to improve accuracy/acquisition and stabilise the balance handling of the weapon. In addition, a tapered barrel means that chamber pressures are higher, leading to increased round velocity.

In cartridges, this usually helps in chambering/unloading the weapon. This differs from shouldering/bottlenecking, which only refers to the case head of the cartridge that holds the projectile, whereas tapering usually refers to the angled sides of the cartridge.