Troy MRF Rail Review PART 2: Installation

The Troy MRF CX 12" on a Colt 6920

The Troy MRF CX 12″ on a Colt 6920

In PART 1 we talked a little about our rail of choice for this project, and why features like “Anti-Rotation” tabs are necessary on weapon systems that we stake our lives on.  We received a brand new Troy MRF CX 12″ in the mail and, after reading the directions, began the installation process.   (Like we need directions…)     😀

Like we stated in part one, the Troy MRF we received is a two piece rail with a monolithic upper appearance (it fills the gap between rail and upper with material, in this case aircraft grade aluminum and rail).  This particular rail required me removing the Delta Ring, Weld Spring, and front sling loop and a little from the sides of the bayonet lug to provide a truly 100% free-float from the barrel nut forward.

Step 1. Prep

Saftey!!!!!   We double, tripple checked (Visually and Physically!) that the rifle was unloaded.  I also recommend removing the bolt from the upper to further reduce the possibility of a negligent discharge when working with firearms and leaving then unattended in vices on workbenches etc.   For many tasks like this, it is also sometimes helpful to remove the upper completely from the lower receiver.  In this case, I kept it on to allow me to kneel on the stock in order to keep the rifle still while dremeling as we were working outside and not on the bench.  Covering the rifle with plastic and masking tape also greatly reduces cleanup later.  The dremel can produce fine shavings of paint, steel, and aluminum.  It is also a good idea to protect yourself with gloves, masks, and as always, eye protection.

Step 2. The First Cuts

Carefully dremeling the Delta Ring off is faster than using a hacksaw.  Be careful to not cut too deep and hit the barrel nut beneath the ring.  Try to align your cut with the natural dips and ridges in the barrel nut and it will be easyer to cut almost all the way through without hitting the steel beneath. Hear are some quick dremeling tips you may find helpful:

  • Note the rotation of the dremel and the direction of flying sparks and shavings and try to position everything to direct these away from you.  Safety First…
  • Don’t use too much pressure; let the tool do the work.
  • There is a proper rotation speed for each tool and material; check your owner’s manual for this.  Too slow and you will have a hard time cutting, and too fast may send pieces of the cutting wheel flying in all directions.
  • When cutting through something like the Delta Ring, you may want to remove the cutting wheel/disk from the cut every so often to see if you are through or not.  Use caution when replacing the wheel back into the cutting channel you were previously cutting in as the dremel tends to skip about a bit.
  • Working on steel and similar materials, it is easy to burn the material when cutting for too long.  Let the steel cool periodically to avoid damage from heat.

Step 3. Removing the Delta Ring

With two cuts made on the Delta Ring, one on each side, we should be able to bend the ring back and forth a bit until it snaps in two (depending on how deeply we made the dremel cuts). Gloves and pliers are helpful here as well as this material we cut tends to hold heat for a bit.

Step 4. Removing the Weld Spring

Using pliers we removed the Weld Spring from the Barrel Nut and since we were wearing gloves, did not mind the spring snapping back at our knuckles as it popped off.

Step 5. Cleaning and Degreasing

We spent about 10 minutes cleaning up the rifle and degreasing the barrel nut.  This is a vital step for two reasons:

  • Metal filings in the eyes are not fun during a gunfight, or at any time.
  • Oil on the barrel nut will set us up for failure later.  After installation, the rail may seem stable, but under the vibratory powers of recoil, the rail may shift a little.  (This is less of an issue when the rail features the “Anti-Rotation” tabs we were talking about earlier as the rail will not rotate more than a few degrees.)  Thank you Troy.  :)

Step 6. Truing and Mounting

Following Troy’s instructions, we trued the rail before criss-cross tightening the 4 Locktite-ed mounting screws (in this case using a short length of picatinny riser).  Our specimen was just about perfect; it aligned perfectly with our upper and when running one’s finger along the top of the rail at the joint between it and the upper one did not feel a crevice or bump between the two.  I expected no less from Troy.  Torquing the screws with a torque wrench after confirming alignment we then snugged the last retaining screw on the lower half of the rail, completing our mounting job as per instructions.  But we were not quite finished…

Step 7. Final Steps and Fin

When a Weapon System may be used in a life or death role, I like to give myself all of the advantages I can.  In regards to a mounting job like this, I give extra thought to the small fasteners.  Using white appliance epoxy I painted small reference marks onto the screws on the bottom of the rail.  I do this with all small fasteners.  Scope mounts, BUIS, etc.  As many readers may already know, these marks provide us a visual indication of a screw should it begin turning after thousands of rounds of recoil (which should be rare as we used Locktite, but I like my chances more when using Locktite and screw rotation indicator marks.)

The rail mounted, we took it out for a few more photos before the Sun went down; the Troy MRF CX 12″ in all of its glory as the evening’s last rays swept the workspace I had spent the last hour in.  We had taken a few extra steps, but had done everything correctly; dremeled, torqued, Locktited, and reference marked.

One thing was left to check, and that was how much accuracy could be wrung out of this particular build now that the barrel was free-floated…  😀

So stay tuned for Troy MRF Rail PART 3: Accuracy Testing


Stay Safe,

-Gúru Chia

Installed and 100% Free-Floated...

Installed and 100% Free-Floated…

Closeup Gallery:

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