This is an installation guide covering the install of a Rainier Arms FORCE Rail. The Rainier Arms FORCE rail is the newest rail in their lineup and is used in all of their RUC Mod2 Rails as well as some of their Custom and Combat Uppers.

Manufacturer: Rainier Arms

Item to be Installed: Rainier Arms 9" FORCE Rail

Purpose of Item: The Rainier Arms Force™ Rail is our latest free float hand guard system. As the name suggest, it was designed with strength and the ability to control your rifle without compromise. Our main focus was to keep it lightweight and durable while keeping the price affordable for our customers. We aligned the 3,6, and 9 positions to accept keymod accessories and to accommodate anti-rotation QD points. These hand guards offer the perfect upgrade for 3 gun shooters, LE/Military and weekend enthusiasts alike.

Parts used for this Upper Receiver Build:

Rainier Arms 9" FORCE Rail
Rainier Arms Billet Upper Receiver
Daniel Defense 14.5" Barrel with Front Sight Post
Rainier Arms RAC Brake

Tools needed:

Action Block
Included Barrel Wrench Inserts
Included Shims
Included Torx Screws
AR15 Armorers Tool
Torque Wrench
Torx Wrench

Before starting any installation or work on your AR15 platform, please make sure you follow the basic safety rules and clear your weapon of any magazine and ammunition. Double check to ensure your weapon is safe. When you open up the package, you'll get the rail itself, a barrel nut, and a package of shims and torx screws.

First, if you're not building a new upper, you'll want to remove your existing flash hider, handguards, and front sight/gas block and tube. You will need your standard armorer wrench, a vise and action block to complete this. For this installation, I simply took some parts I had in the bin. I'll be using a Gen1 Rainier Arms Billet Upper and a Daniel Defense 14.5" with the front sight post. I went ahead and popped the front sight post pins off.

Place the barrel into the upper receiver as you normally would.

Place the supplied barrel nut over the barrel and thread it onto the upper receiver. Make sure you put some moly grease onto the upper threads and inside the barrel nut to preserve the threads.

Once the barrel nut is attached hand tight, take a look at where the screw holes are in the barrel nut as you'll want to line them up approximately 45 degrees from the center when you torque it down. Once you torque it down, the barrel nut will turn approximately 1/8 of a turn or less, make sure you account for this. You may need to use the supplied shims to get it lined up.

Attach the barrel wrench inserts onto a standard AR15 Armorers tool.

Using the AR15 Armorers tool, turn the barrel nut. 35 ft-lbs got my barrel nut to line up where I needed it to be as it turned the barrel nut approximately 1/8th of a turn. Obviously in the picture you don't see the action block or vise. These are very necessary in this step, but omitted because my garage has very poor lighting. Please use the correct setup before installing this rail.

I slid on the FORCE rail to confirm that the barrel nut was turned enough to line up with the torx screw openings. It's hard to tell, but there are "channels" machined into the rail that insert into the channels on the barrel nut.

The billet upper was a tight fit with the anti-rotation tabs of the FORCE rail. I had to gently tap it into place with a rubber mallet. I again confirmed the torx screw holes lined up.

Attach the 8 supplied torx screws.

Reattach the front sight post, gas tube, and brake. You're now finished. The 9" FORCE Rail is the perfect fit on a 14.5" Midlength Barrel.