Originally developed as the PzB39 anti-tank rifle, the GrB39 was an attempt to keep the weapon suitably threatening to enemy armor. The original design, the Panzerbuche (armor rifle) 39, fired a sharply necked down 8mm cartridge, including both conventional tungsten/steel penetrators and an odd gimmick round intended to deliver a payload of poisonous chlorine gas to the interior of an enemy tank. Much like it's contemporaries it was unable to keep up with advancements in armor development, as the average plating grew too thick for a conventional bullet to penetrate. Adjusted to use a blank propellant cartridge instead of a live round, the Grenatbuche (grenade rifle) 39 could launch an armor-penetrating explosive warhead up to 150 meters. An internally rifled grenade cup is attached to the muzzle, and sized to accommodate the same line of grenades made for the 98k infantry rifle, and a sight rig consisting of a fixed notch rear sight and a clamp-on front sight with a set of wire crosshairs for range and a flip-up metal protector is installed in lieu of the rifle sights. Also attached to the barrel are a swiveling carry handle and a folding bipod, with the chamber region marked "cpj/1941". A steel plate with the updated nomenclature "GrB39/21136" is riveted to the top of the receiver next to the "cpj/1941" stamp, with a set of falling block action hardware numbered "5071". The replacement stock numbered "8240", original designed to fold underneath the receiver and barrel for transport, has been subsequently fitted with a set of reinforcing ribs on the interior, preventing folding, and fitted with a leather cover and a partially folding buttplate. One inert grenade is included, along with a cased cleaning kit and assorted documents, including pictures and a German-language manual.