I've had a number of people ask what I would suggest as far as Load/Choke combo for the SA459:
If you shoot TSS: Carlsons Extended .575 $30
If you shoot Fed: Sumtoy .562 (from what I'm hearing, its putting up a little better than the Carlsons)
Of course, if you find another combo that looks great, please share you results. If you have detailed questions, please don't hesitate to shoot me a PM. Hope this helps.