*concentrator*

n. (Mining) 1. An apparatus for the separation of dry comminuted ore, by exposing it to intermittent puffs of air. Knight.

2. (Firearms) A frame or ring of wire or hard paper fitting into the cartridge case used in some shotguns, and holding the shot together when discharged, to secure close shooting; also, a device for slightly narrowing the bore at the muzzle for the same purpose. [ Webster 1913 Suppl. ]