Re: new rifle
Do all the same reloading tweaks that you would do for a smaller cartridge. The AMax bullets are some of the best you can shoot.
Watch the throat and try and get that bullet as close as possible. If this has a machine gun chamber, the throat may be too long to be much good. Setting the barrel back would allow for a better chamber to be cut.
Biggerhammer.net has an excellent board on all things 50cal. Also, consult 50BMG clubs, FCSA.org. They usually have chat boards too.
Have fun with the really big stuff...