K bullet

Also: Patrone SmK (Spitzgeschoss mit Kern) 7.92x57 mm Mauser

The standard 7.9x57mm IS caliber 'K Bullet' as designed before the Allied Invasion. Note the tool-steel core protruding from the rear of the bullet to form a boat tail.

A tracer variation of the 'K bullet', "L'spur (gelb)" or 'Tracer (yellow)'.

The K bullet is a 7.92x57 mm Mauser caliber armor-piercing bullet which has a tool steel core and which was designed to be fired from a standard Mauser rifle. It was used by the German infantry against the first British tanks in World War I. The K bullet had a probability of approximately one-third to penetrate armor 12-13 mm thick up to a distance of 100 meters.

The Germans made several versions of the K bullet during World War I and World War II, including:

Designation	Full Name	Description
S.m.K.H.	'Spitzgeschoss mit Kern, Hart'	Replaced the tool steel core with a tungsten carbide core.
S.m.K. L'spur	'Spitzgeschoss mit Kern, Leuchtspur'	Has a shorter steel core, and includes a tracer composition. May include color designation such as "(gelb)" which means "(yellow)".
S.m.K. Ub.m.Zerl.	'Spitzgeschoss mit Kern Übungsmunition mit Zerleger'	A very rare practice bullet which self destructs after a certain distance.