Brinell hardness and understanding tensile strength values of lead alloys are key factors in making lead bullets shoot superbly accurate. I don't have much use for the Lee publications because most of them are nothing more than information obtained thru other sources of research. NRA and Lyman publications dating back thru the last 4 decades are far more valuable and so is the work and testing done within the Cast Bullet Association. Another total waste of money is the RCBS cast bullet manual. There are several hardness testers on the market that provide a fair approximation of Brinell hardness but it isn't really necessary to have an exact value to get good results. Just learn which alloys are rated as soft, medium, hard or heat treated (quenched). You'll find that best results are often obtained with soft or medium hardness. Hard bullets are often a compromise for poor fit or trying to make lead bullets do things best handled by jacketed bullets. Rich P