Sorry, maybe I'm confused about this, or maybe it just is not clear in this thread.

I thought that the bolt slides on the rails, but the rails DO NOT slide in the upper polymer slots. That is, there is no required movement of the rails in the polymer upper slots, other than for purposes of installation and removal.

I though the only purpose of the slots in the polymer was to locate and retain the bolt assembly. Getting a super-slick feeling when installing or remove the bolt assembly is moot. In fact, one could argue that a tight fit might be better for accuracy.

Am I confused?