I agree with SL. I have a White with a .505 bore. Use the MMP short black sabot with a .452 bullet and you will get a tight fit to the bore (I use .452 300gr Gold Dots and XTP's). Another good combo is the MMP orange sabot with a Lehigh .459 277gr bullet.
http://www.lehighbullets.com/proddet...prod=459%2D260