Keep in mind the OP is wanting an AR pistol. A short barrel makes a big difference on kinetic energy for lighter rounds. OP should determine what barrel length they want when selecting a caliber. The link below has some kinetic energy vs barrel length data for 5.56 vs 300blk. If you look around, you can probably find similar data for your round of choice.

https://fenixammo.com/pages/the-ballistics-of-5-56x45mm-vs-300-aac-blackout

I personally would want the better ballistics of a longer barrel for hunting, but do what you do. This is America.