New one on me. Closest thing to that I've heard of is the .50 Caliber Spotter/Tracer. The parent case is the .50 BMG, but the brass is shorter. This brass has a tube that extends from the flash hole, 1/2 way or so into the case. This is to provide for a good, bright trace from the 800 grain projectile. For an explanation of this cartridge and a simple drawing check out Ammo Man, Spotter/Tracer