OK, I have been reading Dano's recommendation that the face of the bolt should stop 1/8 to 1/4 inch in front of the receiver window when the buffer is fully to the rear.  My question is about the receiver extension length.  If the Mil-spec extension is 3/8 inch shorter than a commercial extension wouldn't the buffer (and thus BCG) extend 3/8 inch further to the rear before the bumper on the buffer bottoms out and allow the bolt face to come back further?  Is this when the stack of quarters is necessary?

sounds like you are trying to hard

Does your rifle malfunction?

The milspec extension is 3/8 longer on the outside, but it is the internal dimensions of the extension that matter.