Review of the A.R.M.S. #71L series, Front and Rear Sights Set.

Posted: August 15, 2010 in Optics
Tags: , ,

This is my review of the A.R.M.S. #71L series, Front and Rear Sights Set.


  • Designed to allow attachment to all Universal Dovetail 1913 and Weaver style Rails.
  • Both are made from durable, metal-reinforced polymer and are a good option when seeking a quality sight.
  • Both are .610″ when in the folded position, from the top of the receiver.
  • A regular flathead screw is used to tighten the mount.
  • The #71L-F (front sight) is rail mounted with a quick deploy latch.
  • They are held open/in the up position by the spring tension.

Adjusting the A.R.M.S. #71L Front Sight is done just like a regular A2 front sight. The pin is actually on the left side instead of on the rear. I highly recommend getting an A2 front sight tool, in particular the skinny one, as it will make it easier to adjust and it won’t butcher the sight.

1. $37.
2. Easy to deploy.
3. Adjusts like a regular Front Sight.
4. Low-Profile (.610″). (Troys are .460″).

1. Should not be mounted on railed gas block due to the heat.

Adjusting the A.R.M.S. #71L Rear Sight is done just like a regular rear sight. The A.R.M.S. #71L Rear Sight uses the Same Plane Rear Aperature with notches on top for CQB shooting. After using many different rear sights, this is by far my favorite (Same Plane Aperature with the CQB Notch.). I did some CQB clearing drills and to use the CQB Notch, all I have to do is slightly raise my head and look through the CQB Notch to the front sight. In theory, this should be dead on at CQB distances. I will test this out when we do our qualifications at work and update this with the exact range.

1. $54.
2. Easy to deploy.
3. Adjusts like a regular Rear Sight.
4. Low-Profile (.610″). (Troys are .460″).
5. Same Plane Rear Aperature with CQB Notch.

1. Small aperature goes forward when sight is deployed.

I was skeptical of replacing my Troy BUIS with “plastic” sights, but after using the Magpul MBUS for over a year, I felt very comfortable with using Polymer Sights. I even managed to drop my AR from the top of the couch (3′ tall) and it fell on the floor with the A.R.M.S. #71L Sights open and they held up. I highly recommend these.

I should mention that when I purchased the A.R.M.S. #71L Front and Rear Set, I had a problem with the A.R.M.S. #71L Front Sight. When zeroing the sights at 50 yards with my LMT Piston Upper, the I was initially hitting 12″ low on the FBI “Q” target (12″ is at the bottom). I adjusted the A.R.M.S. #71L Front Sight all the way down and I was still hitting 4″ low. I replaced the A.R.M.S. #71L Front Sight with the previous front sight that I had on and it was dead on. I later contacted A.R.M.S. and they told me to send the A.R.M.S. #71L Front Sight in to get it looked at. I received a call back within a few days and they advised that there was something wrong with the mold and they had to adjust it. I received my new one in the mail a week later and this time, it was right on at 100 yards. Matter of fact, I only had to make slight adjustment to the A.R.M.S. #71L Rear Sight.

Just wanted to post a little update on these sights.  Since I purchased the ARMS #71 front and rear set, these have been my primary optics on my LMT Piston AR.  I have not had any problems until recently, which is a known issue with the ARMS #71 Rear.  When I deploy the sight, the small aperature slightly goes forward with the momentum of the flip.  This is more of an annoyance than anything else.

  1. Dan says:

    You would really trust this site in a life or death situation? I am not slagging polymer (glock and others) just noting your comment about using it to replace your Troy BUIS. That is a hefty statement.

    • I definitely would trust these in a life or death situation. I’ve been using the Magpul MBUS since they came out and the MBUS are very tough, just like the ARMS #71. And after dropping my AR from the couch and seing it land on the tile floor right on the ARMS #71 sights without breaking them, I am sold. When the AR fell, the ARMS #71 sights were in the up position.

      • David says:

        Hi-I just took my new RRA AR with these sites out for the first time. They left me scratching my head. Question: Do the examples you’ve used deploy to a fully upright, 90-degree position? Neither the front nor rear does on my AR…They both stop at about 87-88 degrees, just short of fully perpendicular. This isn’t a spring strength issue…They cannot be pushed fully upright. This doesn’t cause a visible problem, but sure doesn’t seem right…

      • Paulo Santos says:

        That is how mine are.

  2. mike says:

    Great info.
    OK. here’s my question. I’m debating between the Mag Pul and the ARMS buis . Having used them both which would you say is better??

  3. mike says:

    …with price not being a factor….

  4. mike says:

    Are the Gen2’s even out yet?? I think the only changes are a tad lower profile when closed right?

    Thanks for your reply

  5. Eric says:


    I am getting my first AR, kinda wonder if I should get rear MBUS Gen II or ARMS 71L-R. What’s your thought?

    Also, are they compatible the standard A2 front?


  6. Larry S says:

    Hello –

    You said – “When I deploy the sight, the small aperature slightly goes forward with the momentum of the flip”.

    I’ve just purchased the rear site and intend to use it with the standard AR sight. This is the first concern I’ve heard of.

    How do you remedy this? do you just push it back in place?

    In case I don’t make it back to this site anytime soon – would you please e-mail me about this? correus @ yahoo . com


    • Are you using your AR for serious use. If so, I’d test out the ARMS real well to see if it holds up. Deploy it a lot of times and see if it starts acting up on you. It didn’t start acting up for me right away. You can’t remedy it. And if you are using your AR for serious use, it can be very bad because when the ARMS deploys, the small aperature goes slightly forward and you cant use the small or large aperature at all. If you want an affordable BUIS, check out the new Magpul MBUS Gen 2.

  7. Milspec says:

    For those worried about the small aperature going forward when you push the button of the rear sight there’s a simple fix. Just push the button with your thumb and keep it on the aperature as it raises into place. It’s easier done than said.

  8. […] Review of the A.R.M.S. #71L series, Front and Rear Sights Set. | Paulo Santos Weapon Review Blog […]

  9. Scott says:

    I just bought a set of these for both the front and rear. I took the rear off before shooting and replaced it with a magpul.
    Additional cons.
    1. the roll pin that holds the latch in is loose and slid to one side letting the latch become sloppy
    2. the design of the flip up and it’s engagement area with the latch requires that you push down on the latch to secure the flip up.
    I too had problems with the aperture flipping forward up and it is just too loose for my tastes.
    I’d leave it for airsoft.

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