METALLURGICAL ANALYSIS OF 5.56MM BULLET, COPPER PLATED-LEAD CORED

Samples of 5.56mm bullets, copper coated and lead cored, representing two production lots lots A and B, were analyzed. The purpose of the analysis was to ascertain metallurgical properties and characteristics of each lot which relate to quality and possibly to method of manufacture. The testing procedures included chemical, metallographical, electron micro-probe and hardness analyses. The results indicated that the electroplating quality of Lot B was superior to that of Lot A, especially with respect to adhesion and strength of coating. The electroplating techniques used in the manufacture of each lot were different as evidenced by Lot A having one continuous layer of copper and Lot B having a banded structure of three distinct layers of copper. Although the lead-antimony substrates of each lot were very similar chemically, it was demonstrated from the relative differences in hardness and hardness patterns that bullets of Lot B underwent more work-hardening than those of Lot A.