Installing the Mako MWG M16/AR-15 Magwell Grip
Update: After testing with most available AR lower recievers, a modified MWG was used as a pattern to rework the design. All MWGs currently being produced should be a drop-in fit on all standard military and civilian rifles, carbines, and AR-15 pistols. However, there may be some of the original version still in stock with dealers. If your MWG is not a drop-in fit on your weapon, follow these simple directions.
On many AR-15 receivers the MWG is a drop-in fit. On some, however, the MWG will require slight fitting. Fitting should take about 5 minutes.
I recommend using a Dremel tool with a burr type cutting tip for working with polymer. A stone type grinding tip can be used, but will build up heat quickly and plug up with material. A file may also be used.
If fitting needs to be done, it should be done on the front part of the MWG, not the rear. If the adjustment is made at the rear, the MWG will sit too far forward and prevent magazines from dropping free. Be sure to do all fitting work on the MWG and not on your expensive lower receiver.
There are two areas that may need to be fit depending on the receiver. The first is the radius that fits under the pivot pin area. In this area carefully remove material from the MWG with a file or a Dremel tool until the MWG fits as high as it needs to. The bottom of the magwell should align with the bottom of its groove in the MWG. The second area is the front of the groove that fits the lip at the bottom of the magazine well. The shape and size of this lip varies greatly between AR receivers. If there is an issue with fit in this area, the solution is to open up the part of the groove on the MWG that fits around the front of the magazine well. The MWG should be fit so that the bottom of the magaxine well fits tightly against the bottom of the grove in the MWG. Make the same adjustment to both sides of the MWG so that the two halves align when installed.
Many AR receivers require no fitting. Others may require fitting in only one of the above areas. Before you begin cutting, lay one half of the MWG against the receiver, fitting the back first, and then see what fitting, if any, is required at the front. The MWG should fit snugly, but should not require much force to fit. If the fit is not right, do not attempt to force the fit by drawing it into place with the screws, as you may break the MWG or strip the screws.