While this will also work fine for AR15 upper, it is primarly for those with a transferable M16 receiver.
The hand guard removal tools work very nicely and probably will not cause any damage, however, with the cost of a transferable M16 being near $10K, one may have a little more concerned about adding any stress that one can control.
Thus to preclude any addtional stress on the M16 lower mag wall, one can drill the bottom of the white plastic upper receiver vise block that inserts into the upper. Then with the upper removed from the lower and the block installed you can use the new hole in the block as the pivot point.
The hole should be located in the center of the block and at the same location at the front of the mag well.
The images were "borrowed" from CMMG Inc