All, Taylor's concerns re WW roundballs notwithstanding, I sometimes cast RB's of WW alloy because I have more of it on hand than Pb. A couple things about WW's: Sb and Sn content has varied over the years, but both are minimal now (economics I suppose + metal that's been remelted who knows how many times). Also, finding a Pb-Sb-Sn wheelweight is becoming more difficult as they've been replaced by Zn (Don't use them!) or Fe. As for RB's, my nominally .50cal (.492", RCBS mould), casts ~.0005" larger with WW's than with Pb and weighs ~4gr. less. I find NO difference in starting the harder ones even when using the same patch material than I do the ones I cast from pure Pb. And, yes, accuracy has been indistinguishable in my rifles.