Has anyone out there come across lead coww that vary in hardness? I've got 100 pounds, give or take, and they are for the most part about equal in hardness. I've gone through each weight - painstakingly slow, to remove all the Zinc, steel and plastic weights and tested each weight with a pair of wire cutters (all me paranoid). I've noticed around 4% or so are almost twice as hard as the remaining weights. They are easy to cut through with wire cutters, but take around double the pressure to do so. Is this normal?