Explaining? Sounds fun... I like complicated details.
I would suspect that if there is sufficient pressure to run well, that a slightly heavier buffer wouldn't pose a problem. A bit heavier would take a little longer to overcome the inertia, but the speed of rearward travel would not be affected very much. A slight slowing of the cycle rate, but still plenty of oomph in the system as the added weight will compensate for the slightly lower speed.
With the speeds involved, we only need a few microseconds of delay for pressure to drop enough.
Funny thing is... I believe my bolt carrier is already a little heavier than standard, as it is a "match" carrier, with a little less material removed around the rails. So it seems the difference in gas port size between the barrels must definitely be different.