I'd sort them by weight before loading ANY of them! I would then take one from the heavier group and one from the light group, set them end to end in a vice and squeeze them hard. Measure the lengths of each bullet. This will give you an idea where the hardness levels are. IF (big IF) he's like most hobby casters, he used what ever he could melt for bullets. If they look well filled out, I would use them for plinking using mild to mid level powder charges. The visual inspection could tell you if there are different molds involved. If plinking isn't what you want ,you CAN always remelt/cast to what you do need!