Claim: The K bullet only made a single type, the S.m.K., which was a standard steel core armor piercing bullet with a red rim around the primer.
Evidence: The Germans made several versions of the K bullet during World War I and World War II, including: 
S.m.K. S.m.K.H. S.m.K. L'spur S.m.K. Ub.m.Zerl.