Okay, you have a new Colt rifle, and the rifle has some play between the upper and lower, and it bothers you. What is the solution? Well, Colt, FN, LMT and other military contract rifle manufacturers made the M4 and M16 to throw in the mud of Vietnam or withstand the sand of Syria or whatever crap can get into the operator's gun in Niger. In other words, the play or slop between upper and lower is normal.
When you buy a fine rifle, not mean for battle if it has a solid fit, and you want your mil spec M4 or Mk18 rifle to have that feel. The Accu-Wedge is the answer. This small rubber piece will create a small gap in the rear of the upper and lower connection that will keep it still and remove the sloop or back and forth feel.
The Original accurizing wedge will improve upper and lower fit, and improve accuracy. The wedge is placed in the lower receiver beneath the rear take-down pin. The product may require minor trimming at the base for an ideal fit.
Our founders swore we would not be the Ace Hardware store of gun parts. We do not want to be Brownells. But, we also realize that as you are buying a lower or a full upper component that you might want this part, so here it is.