It should be mentioned, and I will include this on the product page.. the heat shield does have minor amounts of play where the boss meets the optic rail, I am talking thousands of an inch, which are necessary for the tolerances of machining. After 2000-3000 shell on my receiver, it does show a small wear mark due to the heat shield rubbing against the receiver. This mark can probably be covered up using some Birchwood Casey aluminum black if one decides to get rid of the heat shield down the line, but I haven't tried to blacken the shiny spot.
There can be ways to eliminate the play, such as a ranger band going around the heat shield and the mid barrel guide ring for example, or a ranger band around the heat shield and the forearm, or anything that will snug the heat shield down toward the hand guard.
For me, and I realize I am not like everyone, a little mark on the receiver isn't a big deal, but I did want to be up front about this. Here is a picture showing what one can expect perhaps after 1000-3000 shells (i'm not sure when the rub spot presented itself). It is obviously not visible when the heat shield is installed.