concentrator

 An apparatus for the separation of dry comminuted ore, by exposing it to intermittent puffs of air.  Knight.

 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.]