Steve,
Based on conversations with a number of bullet makers, plus some testing of core hardness, MOST manufacturers of swaged, jacketed rifle bullets use a significant amount of antimony in their core lead. In fact the average percentage is similar to that in most "chilled" shot, about 3-4%, but can vary from 2.5% to 6% depending on the specific bullet. Some companies, in fact, often tweak the percentage of antimony, due to performance reports, accuracy, etc. In fact, back before Hornady developed the Interlock jacket-ring, their Spire Points had a better reputation for penetration than some other cup-and-cores, and I later found out that their big game bullets had a higher-than-average percentage of antimony in the cores than most other brands.
