jrkrk
For a 1/20 twist you will probably need a loong bullet to get it stabilized, the one UC pointed out is certainly long. Here is another bullet that might do very well in that 1/20 twist. I shoot them from my White (1/24) and they are really accurate and deadly.
Take a look at the Lehigh .40/200 cal - it is really long and with that twist rate you will need a long bullet.
In my 45 I shoot 110 grains of T7-2f, the 200 grain Lehigh and a Harvester 45 cal sabot.