The honest answer is you are going to have to test them to find out. It's hit or miss.
The follower is designed to present a 5.56 cartridge into the chamber at a certain upwards angle, and towards the center of it. When you load the wider 6.8 cartridges in that mag, the follower will not present the projectile high enough ( though you might get by ), and it will spread the mag, allowing the cartridges to point outwards some. With a polymer mag, you can't adjust the feed lips to fix the issue. Many times the bullets will hit low or outside the feedramps and jam. I would test it with whatever ammo you're going to hunt with, shoot at least 20 rounds and see if it feeds. Nothing worse that having to clear a jam on a follow up shot when $15 ( sometimes less ) would have prevented it.