Just wanted to move this out of the other thread (
http://xcrforum.com/index.php?topic=103.30) and move it here for discussion.
Regarding the upper/lower fit on the XCR: I think i am in a fairly unique position of having 2 different XCR uppers on my same lower (first upper was replaced under warranty, see my afrcom posts.) My two uppers definitely fit different, this second one has a noticeably larger gap between itself and the lower. The gap is largest at the angled section shown in the photo, where it is 1mm. However, there is no place on the entire length of the receiver where the upper and lower actually touch, including the vertical portion at the rear.
The most interesting part I think though is that if I put the halves together without the rear latch (ie: no recoil spring) they mate perfectly, with no gap at all! So it is not the receiver that is causing the gap, but rather the rear latch mechanism that is holding the two halves apart.
With my first upper, when I held the latch and put the two halves together they would go snug and the latch would close without movement of the upper. On the new upper I can feel the latch push the two halves apart slightly when it closes; anyone else notice that as well? I am wondering if its just a tolerances thing or if the dimensions have changed slightly.
