Other than use in a squirrel rifle, I cannot imagine a use for pure lead buckshot as it would not pattern as well as alloyed. It is surprising how much a little tin or antimony will harden lead, but likely not so much to matter really. Just make them harder to load. I have had days when I thought critters "jumped the flash" as I know I could not have missed that shot. Targets can do that too on some days, no matter how well I staple them down. Seriously, even with modern rifles I have made less than perfect hits because the critter decides to take a step during the trigger sqeeze. You just start to pull the trigger, theres no going back, and the critter moves. Had that happen on a couple of deer that got hit less than ideal. Easily could miss a small game animal.
DP