I do not shoot ELR although I find the information on this site and others very interesting. As far as ELR cartridges go, there seems to be a big gap between the .40 cal rounds and the 50 BMG. One thing I read, was necking a BMG down to .40 would be too overbore and not allow a good powder burn for the slow powders of that size cartridge. My question is: Has anyone built a custom BMG in say .45 cal? or maybe .475? I know the bullets in these calibers are usually blunt, but if you are using custom lathe turned copper, brass or bronze, what difference does it make. just the wonderings of an idle mind, but what say you?