Interesting. I have some fairly hard 310gr. .375's lubed with Rooster Red that I sized down for the 9.3x62. That worked just fine, as well
as some 250gr. from my RCBS mould lubed with Lyman Moly. Pure lead, or close to pure lead would likely distort badly. When I made this post,
I did not consider that aspect.
I used my bullet drawing die and that in itself might have been the reason mine didn't distort.