View Full Version : Midwest Industries Rail install and pictorial review

22 June 2007, 10:51
Weapon System: AR15/ M16

Manufacturer: Midwest Industries (http://www.midwestindustriesinc.com/)

Item Installed: MI-20 Rail (http://www.rainierarms.com/?page=shop/detail&product_id=440)

Purpose of Item: A free floating rail allows for multiple attachment points of equipment, to include optics, vertical foregrips, lights, lasers, and other items. A FF rail also allows for better accuracy by the barrel not being touched by the forearm. For many users, it is more a matter of a stable handguard/ rail that will not rattle or wiggle under hard use than it is absolute accuracy.

Tools Needed:
(2) Towels or rags
Cutting tool (dremel or hacksaw will work)
Screwdriver (flathead)

Items Included:
Allen head screws
Allen head wrenches
Locking solution

The Midwest Industries rail (MI-20) is a Free Floating Rail designed to be installed and used on a standard AR15/ M4 carbine. This guide does not act as a substitute for real world knowledge, and is not designed to turn the reader into a professional “gun plumber”. However, it is my belief that the overall installation process is simple enough for anyone who is familiar with the AR15, and has a basic level of skill with simple hand tools. This is based on my own method of installation, and all liability is with the end user. If you stab yourself, shoot yourself, or find some other manner of getting yourself hurt, you are responsible for your own actions. If you have doubts, get help.

With the above out of the way, let’s make sure that we are starting with an empty weapon. Once that is done, remove the upper receiver, pull out the charging handle and bolt carrier group (verify the chamber is empty a second time), and lastly, pull off the handguards.

You should now be looking at something similar to the below picture.


Take your box with the MI-20 rails. You should find a plastic bag with 2 different size allen wrenches, several different allen head screws (2 different sizes), a locking compound for the screw threads, and the four primary components of the rail. Below is a picture showing the 4 rail parts.


22 June 2007, 10:51
The Delta ring assembly must be cut off in order to install the rail, and this is the part that seems to scare people the most. In order to prevent raking the upper receiver or barrel with your dremel cutting wheel, or hacksaw, it would make sense to cover these parts.

In the below picture, you can see that I covered everything except the Delta ring with shop rags, and then I taped them in place. By wrapping the rags around the parts, they have several layers of protection.

With the upper protected, take your Dremel with cutoff wheel, hacksaw, or other metal cutting implement, and make a cut in the Delta ring.


By making a cut on each side of the top (not into the gas tube!), you will have enough clearance to remove the Delta ring. I didnít cut all the way through, and I used a flathead screwdriver to twist inside the cut and pop it free.


With the Delta ring shell out of the way, you can now see a coil of springs. By using pliers, I compressed the springs, and twisted them off the barrel nut. The below picture illustrates the method.


This is what the assembly looks like with the spring out of the way.


22 June 2007, 10:52
Lets look back and make sure we have the four main parts of the MI-20 rail. Match them up with the below picture. There should be the wider upper rail, a thinner lower rail, a narrow “U” bracket which will go in front, and a wider “U” that will lock the rear into place.


Take the thinnest “U” bracket, and with the two smaller Allen head screws, install it into the lower rail. There is no need to make it tight, or to use the locking solution on the threads at this point. For right now, we are fitting everything into place, and will tighten it down later.

In the below picture you can see these two pieces mated together.


Match the cutout in the upper rail to the teeth in the barrel nut. It will press into place and should look like the below picture.


With the upper rail in place, find the left over part which resembles a wide “U” with 4 holes drilled for allen head screws. Mate this with the upper rail, and install the 4 screws. Do not tighten these down yet, just leave them a little loose.


22 June 2007, 10:52
Now its time to place the lower rail into position. You should now be looking at an almost completed rail similar to this picture.


Once you have gotten to this point, its time to grab the locking solution and both of those Allen wrenches. You need to go back through, and tighten everything up, as well as put some locking compound on each screw. Make sure that you tighten the screws the same way that you would lug nuts, which is a little at a time, and alternating sides. If you crank down on a screw without alternating, you will pull the other screw holes out of position, or possibly even damage the rail. Use common sense, and get all the screws snug before you are done.


CONGRATULATIONS! Once you are complete, you are ready to assemble your weapon, and check everything out. Optics, lights, lasers, and vertical foregrips are all ready for mounting.

While not shown in these pictures, you may want to consider getting rail covers to protect your new investment. The aluminum rails are tough, but can cut into things like the sheetrock corners inside your house, or can be damaged if you knock them into concrete or steel.

22 June 2007, 10:52
Some additional pictures.