Most AR owners are aware of the sometimes sloppy fit between the upper and the lower on our platforms. Even the manufacturers have come up with a so called fix for the problem.

Unfortunately the so called fix doesn’t really solve the core problem, it only side steps it.

I found a much simpler fix that actually solves the real problem, ie too much gap between the upper and lower. The magic ingredient is foil tape. Pretty simple stuff, just use an appropriate amount of layers to eliminate the gap without creating undue pressure on the takedown pins.

The foil measures out at .0035 on my calipers. It took four layers on mine to hit the sweet spot at the rear pin (total thickness .014) and two layers right by the forward pin (total thickness .007) . Works so much better than that pain in the ass screw under the grip……