Originally Posted By: Steve_in_PAThe loose fit between the upper and lower receiver have nothing to do with accuracy.
The barrel, chamber, bolt and firing pin are all encased in the upper receiver. All those parts contribute to accuracy, especially the chamber and barrel. Installing an O-ring or one of those wedges is more about a mind game with the shooter rather than solving an alleged accuracy issue.
So......glass bedding a rifle is also a mind game???? Barrel, chamber, bolt and firing pin are also all encased in the receiver. Make no mistake about it, movement between the barrel and the stock absolutely, definitely affects accuracy. You want zero movement and I would love to know just what kind of earplug is hard enough to cut and use as an Accuwedge. The JP Enterprises device works the best, followed by simple set screws drilled and tapped into the lower, then the Accuwedge. A simple $4.00 Accuwedge will tell you if that is your problem. I would suggest a really good bore cleaning too, such as with JB Bore Cleaner.