I know this depends on what you're willing to accept, and have read the threads where folks describe what they consider fatal flaws. I've also read about the techniques that help keep the unmentionables to a minimum (heck, I've contributed my limited experiences to the piles of recommendations), but what I'm interested in knowing is, when you're in the zone, casting as well as you can, can you realistically expect all or nearly all, not just keepers, but nigh on visually perfect boolits?
I think I've gotten close on occasion, when I'm rested, the weather for my outdoor casting is cooperative, and I run just one or two pots worth of alloy (35 to 40#). Using a preheated 8 cavity aluminum mold and discarding the first one or two pours, I'll keep 98%, with 95% looking very good up to no defects noted. But it's harder the longer I cast, with the cadence, pouring technique getting less consistent with fatigue.
Maybe it doesn't always matter (for instance, I tumble the boolits together in coating them and those perfect edges don't stay that way), but I'd like to know what the acme is.