Dear all:
Just finished my first "build" with an Anderson multi-cal stripped lower, and Barrier Defense 6.8spc complete upper.  After assembly, I tried inserting both of the new ASC 6.8 steel magazines I bought.......and I'm having an issue.  Both of them will NOT easily slide in to the mag catch.  They go into the mag well easy, but then they reach a certain point where I have to RAP them up with the palm of my hand to finish travel.  The mag catch grabs them at that point, BUT, then I almost have to use two hands to get either of them back out.  I tried a different ASC 5.56 mag, and no issues whatsoever.  Anybody have any advice or guidance on what the issue might be?
Thanks in advance.

Is the 556 mag fully loaded? Sometimes a 6.8 will spread the lips a tiny bit if fully loaded. Back off two and try again.

If you are not having issues with the 5.56 mag, I would think that your 6.8 mags are out of spec.