i'd avoid using battery lead for castig material. there are a boatload of chemicals added to this stuff which, even if you cast out doors, upwind, don't eat or drink while casting, wash hands afterwards, etc., can cause some nasty problems by way of fumes. even trace amounts of cadmuim, aresenic, etc. can trash your day.
BTW, linotype is great, but only for center- fire stuff. i doubt that you would get sufficient bullet upset to properly engage the rifling, and if you did, you're really trying to get one system to function within the parameters of another, so why bother: get the right materials for the job at hand (i risk sounding like a political rant here)
anyway, if you figure out how much lead you actually put down range in an afternoon of shooting, you'd do well to get a good reliable source of pure lead, and be glad of it. why risk your health, and your fine rifles, on a few pennies worth of questionable lead?
thus endeth the tirade.
good luck!
MSW