For starters maybe just buy some commercial cast bullets. Lots of sources, if you google it or ask around for a recommendation. Heavy for caliber is the way to go. If it's a plain jane Russian 91/30 you will need a good fat bullet, at least .314 is my guess. If you get serious about using home cast bullets (they're great) consider having a custom mold made up to fit your gun. I've shot the big Russian 7.62 in some matches, using cbs. Lots of fun. There's guys shooting very small groups this way out to 200 yds. You're on the right track to having fun. Once you have a good mold you're set for life.