Strange I missed this thread up until now.
I have been loading gas checked lead bullets in my .458 SOCOM for a while now. Seems to work OK for me to plink with. I had some cast bullets already for loading in my .460 Weatherby so I tried them. I recently go a LBT "M" style bullet to try in the SOCOM. It is designed for the 45-70 but it has a decent profile for a 400 gr. bullet and shoudl work good.
Something to look at below from L to R:
.460 WBY loaded with a 500 gr. RNGC Lee mould
Old Ideal 390gr. RNGC bullet and loaded round
Lee 500 gr. RNGC bullet and loaded round
Sierra 300 gr. JHP and loaded round
Hornady 500 gr. JSP and loaded round
.460 WBy loaded with 500 gr. JSP