Besides the diameter of the drill bit, using a round drill bit with a stepped top rails, the high part of the drill bit might be behind the step in the top rails, resulting in an even smaller gap between the rails. I know the AGI video says use a 15/64 drill bit, but they used a receiver blank that did not have stepped top rails. Also I think the instructions in the paperwork with the AGI video call for a 17/64" drill bit. Neither size is exactly correct. The specs call for 6.0 mm to 6.3 mm from the bottom of low part of the top rail step nd the top of the lower rail.
Originally Posted by go_home_red