I am in the process of purchasing a 10 yrs old and hardly used BRNO 602 in 458 win (hope the deal goes through!). I want to convert it to a calibre that easily give 2250 f/s withour dangerous pressure, that will feed reliably without major modifications, that I can easily get brass for, and that can shoot standard 458 win in a pinch. I have been trying to read up on this subject in the different posts here, but I must confess to still being confused. Do all of these calibres use standard lenght fireformed 375H&H brass? would it be a good idea to do the fireforming in stages, and to first fireform in my 375 wby? What would be the pros and cons for each calibre? Thanks,

I would shoot the rifle and reload for it like it is first. You may find it has all the power and recoil you need. If you decide to modify it I would definately go with the 458 Lott, mainly because it is now a standard factory round.