View Full Version : Mega Arms MKM KeyMod Upper Installation

9 December 2013, 00:51
This is an installation guide covering the install of a Mega Arms (http://megaarms.com/) MKM KeyMod upper. This guide will work both on the .308 version as well as the AR15 version as the steps are identical. For this guide, we will be installing the .308 version.

Manufacturer: Mega Arms (http://megaarms.com/)

Item to be Installed: MKM KeyMod Upper

Purpose of Item: The Mega KeyMod MKM is a two piece upper receiver & hand-guard. It combines the strength and durability of a billet upper with a sturdy lightweight extruded hand-guard.

Parts used for this Upper Receiver Build:

308 MKM Kit (http://megaarms.com/maten/receiver-sets/billet-upper-lower-sets/mkm-keymod-upper-ambi-lower-set/)
Mega Arms 18" Barrel (http://megaarms.com/maten/maten-barrels/new-barrel/)
Rainier Arms Low Profile Match Grade Gas Block (https://www.rainierarms.com/?page=shop/detail&product_id=1872)
Standard Gas Tube
BattleComp (http://www.battlecomp.com/) BABC

Tools needed:

Included Barrel Nut
Included MKM Wrench
Torque Wrench
T15 Torx Wrench

First you'll see that we've laid out all the necessary parts to be installed. It should be noted that Mega Arms recommends and requires you to use a DPMS Panther "Claw" Block to secure the upper receiver. Any other tools will void your warranty. Mega Arms will also fit your gas block to your barrel for a small fee if you are having issues with the fit. They recommend the following gas blocks with part numbers:

Rainier Arms: Low profile match grade gas block
Stag: Low profile gas block
Vltor: GB-2S
Yankee Hill: YHM-9383

http://i849.photobucket.com/albums/ab55/UWone77/STCK2143_zpseb049bf2.jpg (http://s849.photobucket.com/user/UWone77/media/STCK2143_zpseb049bf2.jpg.html)

As with any upper receiver install, you will want to apply some anti-seize to the barrel extension. This will make getting the barrel on and off at a later time that much easier. Ask me how I know this [:D]

http://i849.photobucket.com/albums/ab55/UWone77/STCK2119_zps18373f56.jpg (http://s849.photobucket.com/user/UWone77/media/STCK2119_zps18373f56.jpg.html)
http://i849.photobucket.com/albums/ab55/UWone77/STCK2145_zpsc83b0fc5.jpg (http://s849.photobucket.com/user/UWone77/media/STCK2145_zpsc83b0fc5.jpg.html)

Next, insert the barrel into the upper receiver. Make sure the alignment pin goes into the alignment slot. Also check to make sure there is no gap between the barrel extension and the upper receiver.

http://i849.photobucket.com/albums/ab55/UWone77/STCK2124_zps25dc6474.jpg (http://s849.photobucket.com/user/UWone77/media/STCK2124_zps25dc6474.jpg.html)
http://i849.photobucket.com/albums/ab55/UWone77/STCK2148_zps3550674c.jpg (http://s849.photobucket.com/user/UWone77/media/STCK2148_zps3550674c.jpg.html)

Ensure you apply some moly grease or equivalent to the barrel nut before installation. This will help protect the threads.Then using the supplied wrench, use a 1/2" torque wrench to tighten the barrel nut to 65 ft-lbs. With this type of barrel nut, no "timing" is necessary. When the torque wrench clicks to the desired value, you are finished.

http://i849.photobucket.com/albums/ab55/UWone77/STCK2120_zps5238a0e5.jpg (http://s849.photobucket.com/user/UWone77/media/STCK2120_zps5238a0e5.jpg.html)
http://i849.photobucket.com/albums/ab55/UWone77/STCK2151_zps45246a7e.jpg (http://s849.photobucket.com/user/UWone77/media/STCK2151_zps45246a7e.jpg.html)

Install the gas block and tube. Then slide the handguard over the barrel into the upper receiver.

http://i849.photobucket.com/albums/ab55/UWone77/STCK2152_zps4915b0c9.jpg (http://s849.photobucket.com/user/UWone77/media/STCK2152_zps4915b0c9.jpg.html)

Using a T15 torx wrench, install torx screws into your MKM. Loctite may be used, but in this case we did not use any.

http://i849.photobucket.com/albums/ab55/UWone77/STCK2153_zps20f4124e.jpg (http://s849.photobucket.com/user/UWone77/media/STCK2153_zps20f4124e.jpg.html)

Your upper should now look like this. We opted to use a BattleComp Enterprises BABC for our muzzle device.

http://i849.photobucket.com/albums/ab55/UWone77/STCK2154_zpsab524f29.jpg (http://s849.photobucket.com/user/UWone77/media/STCK2154_zpsab524f29.jpg.html)

After you put your rifle together, you should always function test the weapon to make sure everything is working properly.

Steve Coulston
11 December 2013, 19:32
Great step by step instruction. Mega makes an amazing product.

11 December 2013, 23:48
Great review....GJR!