As I recall Idaholewis's posts regarding No Excuses bullets, and his Rice & Green Mountain fast twist barrels, he wasn't particularly impressed with them as he felt that there was too great of a weight difference between the 50 bullets in a box.
I do know from reading hundreds of his posts, that the KEY to eeking out maximum accuracy in either of those brands of barrels, is finding the sweet spot in bullet diameter that will obtain the accuracy you desire for the type of shooting that you want to do.
And, I further know, that the kind of accuracy that Idaholewis strives for seldom seems to come from factory bullets. The question that you have to ask yourself, is "Just how accurate do I want this new .50 caliber, Fast Twist, Rice barrel to be?"
Is the rate of twist that you ordered sufficient to stabilize big lead so you can shoot out to 500-1200 yards? With a globe front sight, and a vernier tang long range rear sight? Or, do you just want a super accurate hunting rifle, that if equipped with a decent recoil pad, and a modern scope, will kill anything on earth with huge lead?
A Hankins, or Swinglock, super accurate, super adjustable, sizing die is probably going to be necessary to get the accuracy you want.