Misch metal is an alloy consisting predominantly of cerium and other rare earth elements. It typically contains about 95% lanthanoids (primarily cerium, lanthanum, neodymium, and praseodymium), making it rich in pyrophoric properties which are useful in applications like flints for lighters and additives in the metallurgy of magnesium. The alloy often includes small amounts of iron (about 5%) and traces of sulfur, carbon, calcium, and aluminum, fitting the composition mentioned in the question.
Therefore, based on the given composition details, the correct alloy used in the production of magnesium-based bullets, which utilize the unique characteristics of misch metal for improved ignition properties, is indeed misch metal.