How could or should the 6.5 mm Grendel be improved?

[stanc]

The only issue I have about Grendel uppers slotted onto existing M4 weapons is that they restrict magazine capacity to 25 rounds. A slighter larger receiver and magazine well could allow wider magazines and a 30 round capacity.

With the current stainless steel magazines, capacity is a function of height, not width. Capacity could easily be increased to 30 rounds by making the magazine a bit taller, as was done with the 30-rd Barrett 6.8 SPC mag.

A wider mag well would only be necessary if it were desired to have a 6.5 P-Mag.