I saw "big bores" was posting a message in the Medium rifle section where he mentioned the .600 RGB Belted Nitro Express,,,so i was wondering if someone kind enough to tell me about this one,,and how expensive a bolt rifle would be in this chambering and what would be it's ballistic potential (safe max load,,,ok or max load)!?

The cartridge you are referring to was originally called the .600 Overkill and a photo of it is here:

http://www.serveroptions.com/ubb/ultimatebb.php?ubb=get_topic;f=16;t=001947;p=1

900 grains at 2400 fps. More if you can handle the recoil.