My first reccomendation is up the bullet weight to get the speed down and accuracy at peak.
In other words, I'm assuming 2100 fps is with 250 gr bullet weights, or close.
I suggest a 320 or 340 gr LFN, with gas check, and crimp groove cut so you have a substantial driving band outside the case. I'm sorry, but I've been knocked around a bit too much for the last few months, and have not read about this gun yet, but assume it is based on the 500 S&W? Similar case and cylinder lengths? If so, even go to 400 gr bullets. Definately use LBT lubricant, and if it has ports like the 500 expect some leading forward of the ports, but not enough to hurt accuracy with heavier bullets.