On the 15-22, the takedown pin retention spring is held in place by the grip, as opposed to ARs where it is held in place by the tube. With an aftermarket Magpul grip it will fall into the grip and will not retain the takedown pin. The wedge solves that problem and fill in the gap as well. Not sure how they solve that problem on MOE versions. I have the MIAD grip and wedge also. FWIW I didn't have to file mine to fit either.
What is different with a + version?
Is this concidered a "gap".......May be 1/16 to 3/16" on side and 1/8" on back??