Otto,
With that dia.and wt.,I think it would be worth your while to try different 44 mag cast bullets,sized to .420( or maybe 44-40 bullet,starting at .427).If you start with lubed bullet,simple sizing die w/o holes should work. I sized .439 bulets to .425 for my .404,but had to lube with Alox because lube grooves got wiped out.If you use black powder Alox won't work.Maybe Paperpatch 41 mag bullets,but would be light at about 200gr.I still think opening up your 405WCF mold is a viable option, unless you want to keep it for a 405 rifle.You should be able to buy a .416 standard mold pretty cheap and if too heavy face it off. Let us know how everything works out.
Mike
