(1) A hollow projectile used for obtaining sidewall cores. See [[sidewall core]] and [[sidewall coring tool]].

(2) [[Drill pipe]] core barrel. A hollow cylindrical device from 25 to 60 feet in length with a hollow drill bit which can be attached to the bottom of the drill pipe for the purpose of recovering a continuous sample of the [[formation]] while the hole is being drilled. The sample recovered is a cylindrical core which, under ideal conditions, might be as long as the core barrel.