Memory says the early 8x57 version used a .316 or .318 diameter bullet the 8x57J ?? Might be worth some research
A quick google search shows you can but the .316 cast bullet pretty reasonable
http://westernbullet.com/316oversize30.htmlWestern would have been the go to guy a decade ago but seems to have trouble filling orders lately.
Ebay could be a source of the same molds that Western uses. Unsized bullets from similar molds could be used too.