Tuesday, May 6, 2014

Fortis Rail Installation

As mentioned on my modification of my PSA 14.7" upper, I did have some issues with the installation of my Fortis REV rail. That said, all was resolved with the assistance of a rail mount, specifically my Burris PEPR QD scope mount.

The rail comes in three parts and attaches to the barrel nut; the main body of the rail [1], the lower locking component [2], and four anti-rotational screws [3].

[1] Attached a Rail Mount

This is the key for correct alignment, you'll want to use a rail mount that extends between the Fortis rail and your upper receiver, whether it be an optic mount (like mine) or a carry handle. I used my Burris PEPR QD scope mount.

Simply place the main body of the rail [1] into position. Be careful not to mar your barrel and the barrel nut when installing the rail. Once in place, attached your rail mount. Once the rail mount is locked into position, insert the lower locking component [2], add a small amount of Blue Loctite (if you want to, I didn't), and screw in the anti-rotational screws [3] by hand.

[2] Torque Wrench

If you have it, use it! I have a FAT Wrench that I use for the installation of my scopes, highly recommended whenever installing optics. Over-torquing or under-torque can affect accuracy and consistency. I contacted Fortis and this is what they had to say:

Approximately 60-75 inch pounds.

Fortis Manufacturing, Inc. - "Strength by Design™"
P.253.230.7285 / www.fortismfg.com

I set my FAT Wrench at 60 IN LB and then cross torqued the screws into place.

Once set, I removed the PEPR scope mount.

[3] Finished View

Mind the gap! A common point by many is that there is a gap on the Fortis rail. You'll also notice a slight step on mine, too. Not ideal, but I recently installed Magpul MBUS Pros and I did not have to make any drastic adjustments for elevation. If there had been a problem, I would have exchanged the rail.

Close up view of what to expect when the bottom locking component is mated with the main body of the rail.

A slight gap on the rail tab.

And the money shot.

Final notes. I had initially attempted to install the Fortis REV on a LAR Grizzly billet upper, but they were incompatible. One solution is to cut off the rail tabs, however, I obviously decided against this and stuck with the YHM rail on my LAR upper. The VLTOR MUR uppers do successfully mate with the Fortis REV Rails without removing the tabs, but will have that slight gap between the rail and the upper.

Lastly, I love shooting this rifle as it is very lightweight and ergonomic. Hell, I need to go shoot tomorrow or tonite, been locked up doing freelance work and need some range time.


  1. How has this rail been for you? Several people report that it rotates/moves and messes with the zero of a front sight. Any issues?

    1. No issues on my end. I've never heard of any issues regarding rotation, maybe they removed the tabs that index with the upper receiver? I will have to look that up, thanks for bring to my attention. Now, that said, I mainly run a red dot and that is mounted on the upper receiver and not the rail. I will actually take this AR out in the forthcoming week and run the irons to see if my POA/POI has shifted. I will report back.

    2. Thanks for the response.
      Here are some interesting reads:

      Some of this is trouble with installation and some with qa/qc on Fortis' end. However a few report issues after extended use.
      I am currently plagued by the issue of the barrel being off center. Done everything they recommend and what you detail in your post too. Taking it to a shop tonight to see if that helps. However, I hope there aren't long term movement issues lurking out there for me.

    3. Yes, I do recall reading threads like those, that is why it's very important to have some type of rail mount connecting the upper receiver to the rail when tightening down & aligning. Based on what you've said though, you've taken that necessary step. I will have to say that I was going to return mine to Rainier Arms at one point and if you are having issues, as it's well documented within the shooting community, return it, don't even deal with it and the possibility that the rail might rotate. The Geissele rails are great and I highly recommend them, very easily to install and Geissele factors in everything whenever he designs something. Black Friday is just around the corner too.

      On another note, on the M4 Carbine link (I think) someone posted they were having an issue with a PSA barrel nut, mine is a PSA barrel nut and no issues.

      Let me know what you decide to do by posting back on here, it's important to relay such info to fellow shooters.

    4. Sorry for the long delay. Was waiting for resolution on this issue.
      I ended up getting a refund for the rail.
      Took it into a local shop and they confirmed the issue.
      I can't say for sure if this would happen with all the rails since I only had experience with one example; however, after looking at the design close up I will not being going with a Fortis rail in the near future. Just my personal experience
      A+++++ for Primary Arms for making it right.

      Thanks for your input Blk Rfl Div!