Hello sir For 30 cal you need to use wire of about 6.5mm or 0.26 inch diameter ideally to get the best results. Lead wire composition can vary and can give you a variation in grain size. We recommend pure lead, some additional bismuth, antimony may work in some cases. https://www.rotometals.com/lead-wire-by-the-foot/# You can visit the above website to purchase lead wire, they offer shipping worldwide. Also, we do not have any affiliation with the website mentioned above.