Patronen 318 Anti-Tank round to be used by the Panzerbusche Anti-Tank rifle.  It was also known as S.m.K.H.Rs.L'spur.  This is a 13mm case with a 8mm bullet.  It is armor piercing, tracer and has a tear gas pellet inside the bullet.  The idea was for the round to penetrate the armor and rattle around inside to release the tear gas.  I know of someone who took one of these apart once and verified the hard way that it did, indeed, have a tear gas or pepper spray inside.  The round has a muzzle velocity 3,540 feet per second according to US tests.  The anti-tank rifles became ineffective pretty quickly as armor improved so most the the rifles were reworked to create a GrB39 Granatbusche grenade launching rifle.  They used a  round with a wooden bullet.   Notice the crack in the casing of this round.  You sure wouldn't want to try to fire this one!!