Rob has been doing this for a long, long time and is very good at it... he keeps it simple, has a good cadence and knows what to look for...
When I started out trying to cast I bought some lead that was advertised as pure, but it never tarnished and try as I may, there was a lot of weight variance by a couple grains... I even took to cutting my balls in half and finding teeny, tiny "voids" inside, but since few do that it might have been more common then we'd know...
I then bought "nuggets" advertised as PURE lead but ended up with cottage cheese on top, even with a thermometer in the lead melt..That company also sold Range Lead in that configuration and I returned it for credit and got 5# ingots as when man gets involved, things can go awry... With the 5# ingots I got better balls and more consistency...And they tarnish...
OJoe, I started out decades ago shooting those Hornady swaged balls with precut round patches in a T/C Renegade and got excellent accuracy so yea, they do spoil a guy, but making my own balls is like tying my own flies... sure does add an element to the fun... As for accuracy, I had gooder eyes back then so it may have had to do with that!