The “Sweet Spot”

The AK Master Mount™ side rail is held to the AK receiver wall by side compression. The underside of the two Allen head screws must compress firmly against the right outside receiver wall in order to have the adequate compression needed to keep the side rail tight against the left receiver wall.

So if you are experiencing slight movement of the side rail after installation, remove the Allen head screw from each hex pin to ensure the end of that pin is not flush with the outside receiver wall. Because the receiver walls actually flex inward during tightening of the Allen head screws, you want the shaft end of the hex head pins inset into the right receiver wall. Remember we are working with an AK, so there can be variations in receiver width.

The quickest way to check if pin length is the issue for your side rail’s movement is to add a couple of washers underneath the Allen head screw before installation. Just make sure the center hole in the washer is bigger than the hex pin shaft’s diameter.

This in effect simulates a wider receiver and ensures the underside of the Allen head screw is actually compressing against the outside receiver wall and not just “bottoming out” on the shaft end of the hex pin. Once this diagnosis is confirmed, remove the washers and use a metal file to remove some metal material from the shaft end of the hex pin. Do not worry about removing too much.

The other cause of side rail movement, which fortunately in not very common, is if the receiver’s left sided axis pin holes are not a true, round 7mm hole (out of spec).  Such oversized or misshaped axis pin holes will not adequately support the shoulder of our mounting pins.  This problem is not fixable, and unfortunately our side rail kit is not going to work in this scenario.

Troubleshooting Fitting Issues:

Possibility 1

Unfortunately many AK builders get a little sloppy in their manufacturing tolerances.  If optic mount handle closing resistance is felt, or there is still slight optic mount left to right wiggle despite a hard to close handle, there may be interference on the rounded back portion of our handle.  Background: Our optic mount is the only one on the market where the back of the handle physically rotates into the side rail’s central cut-out in order to “lock” our optic mount into the side rail.  Possible points of interference: (1) the side rail’s central rivet head not flush with the floor of the side rail’s central cut-out.  (2) the side rail’s central cut-out slightly off center (see possibility #2 description below).  Both of these scenarios will interfere with the back of our handle properly rotating into the side rail’s central cut-out.  Clues: look for finish wear on the lower, rounded back protrusion of our handle.  See attached picture for an example of this.  Treatment: use a dremmel / metal file to remove a small amount of material on the back of our handle exactly where the finish wear is seen OR from the top of the central rivet head if this is too tall.  This will provide the needed clearance for the back of our handle to fully close properly.

Possibility 2 

If the side rail’s central cut-out is slightly off center, the rounded back of our handle can hit the vertical edge of the side rail’s central cut-out and cause handle closing difficulty and / or push our optic mount up and away from the side rail.  Clues: look for finish wear on the lower rounded back protrusion of our handle, or finish wear on the side rail’s front surface.  See the attached picture for an example of this. Treatment: use a dremmel / metal file to remove a small amount of material on the back of our handle exactly where the finish wear is seen.  This will provide the needed clearance for the back of our handle to fully close properly.  

Possibility 3

The side rail’s rear rivet head protrudes above the base plate of the side rail and hits the back end of our optic mount when sliding onto the side rail. This scenario results in resistance being felt when the optic mount is slid 1/3 of the way onto the side rail.  The end user misinterprets the resistance to the clamp bar being raised too high. Clues: look for finish wear on the top of the rear rivet head OR a small “ding” at the end of the dovetail cut-out channel on the back of our optic mount.  See attached picture for an example of this. Treatment: use a dremmel / metal file to remove a small amount of material from the rear rivet head OR to make a shallow scalloped shaped recess at the end of our optic mount’s dovetail cut-out channel.  Just make sure to leave enough metal present to make contact with the end of the side rail when the optic mount is installed. 

“Yes, the top picatinny rail of our optic mounts “center” over the center of the receiver”

Because many AK builders get a little sloppy in their  manufacturing, you cannot use external landmarks such as the rear iron sight or the dustcover as a point of reference for “center of bore.” This is especially true for the rear sight as they are often canted off midline.

Take off your dustcover, install the optic mount, and place a tape measure across the open receiver to determine actual midline.

An even better test as you really want your optic aligned with the actual path of the bullet is to place a straight object (such as a pencil, dowel rod, or a large drill bit) into the internal barrel opening so that you have a visual point of reference for “center of bore.”

PSL style side rail

SVD style side rail