Looking to make a round for my .300 Remington Ultra Short Mag that can work on bear out to 600 yards. I was hoping to work up a round with the powders I have on hand which are which are Hodgdon Retumbo, Hodgon H380 and IMR 4350. I know the Retumbo will produce the best but was wanting some help with the best place to start selecting type of bullet; bullet weight and powder. I am willing to buy another powder if need be but was just wanting the gurus of reloading to give me their best advice on where to start. New to reloading this year and just finished setting up the spare bedroom with my x mass gifts. Thanks for everyone's help!