Product Review: The A.R.M.S. Model 71L Back-Up Iron Sights

After deciding he needs back-up iron sights on his guns, Pete tests the A.R.M.S. 71L polymer BUIS sights on his AR pistol.

The A.R.M.S. 71L rear sight

I just installed a set of A.R.M.S. model 71L flip-up sights on an AR pistol that had no iron sights, just a red dot. I bought these because they were a good brand name with a price point which was not as high as Magpul sights, but was higher than cheap no-name crap from China that no self-respecting shooter would put on their airsoft gun.

These are not my first flip-up sights. I have flip up/fold down back up iron sights (BUIS) from Magpul (polymer), GG&G (metal), Yankee Hill Machine (metal) and a rear sight from ARMS (metal), their model 40L. The model 71L has some similarities to the 40L, but the 71L sights are polymer while the 40L are all metal. The 71Ls are easier to deploy than many of the metal sights, including the A.R.M.S. 40L.

Tough Polymer Combat Sights

A.R.M.S. calls them “Tough Combat Polymer Sight” right on their box, and I have to agree with them. This is some darn tough polymer. It feels stronger, rougher, and tougher than the plastic on the Magpul sight. The tab you push down on to release the sight and have it pop up feels sturdier and thicker, for example.

Please note that I said they “feel” stronger, which is subjective. I am not polymer engineer, and I did not subject these to drop testing or other destructive testing. I realize that “toughness” includes not only impact resistance, but flexibility and the ability to hold their shape and zero through a range of harsh conditions and treatment. Nonetheless, the ARMS 71 sights felt reassuringly solid and rugged.

A.R.M.S. 71L front sight
The A.R.M.S. 71L Tough Polymer Combat Sight, front, seen folded and deployed. The main image accompanying this post shows the matching rear sight folded down. Depressing the tab on the read deploys the sight.

While the base and body of the sights are polymer, the internals, pins, springs, front post and rear apertures (there are two sizes) are metal. Adjusting the front sight did not differ from adjusting the front sight on an A2. The rear sight had a good-sized knob and the clicks when you raised or lowered it were audible and tactile. The knob had an arrow with an “R” on it for “right” but at my age I needed magnifying glasses to make out which way to turn it. There is also a small arrow at the front of each sight base so you don’t mount them backwards.

Optics and Aging Eyes

As we age, the lens in our eyes stiffens and our eye muscles can no longer bend it as much. As a result, we lose the ability to focus on close-up objects, a situation that starts in the early 40s and gets worse until about 65. You may see this in people who hold reading material further and further away, but it is less obvious on the firing range. I learned some years back, a blurry front sight is detrimental to shooting small group size.

I remember when I could see the sharp edges on an AR15 front sight post, but to achieve that today, I have to wear reading classes. The downside with reading glasses is that they make everything in the distance blurry. How can someone with presbyopia identify their target and get a clear font sight picture? Easy invest in some kind of optic, either magnified or not.

Some years back, I found the group sizes I shot with a red dot were half to a third the size as group sizes I shot with iron sights. That was a turning point, and I gradually added red dots or other optics to as many guns as possible. Some guns only had a red dot. After pulling one out of the safe and finding that the battery was dead, I decided all my guns should have back-up iron sights. After all, a shot with a fuzzy front sight is better than a shot with no sight.

The importance of a BUIS goes double in a survival situation. While I try to carry at least one spare battery in the pistol grip or stock, you might face a situation where you don’t have time to change batteries. There might also come a time when you have no batteries and resupply is unlikely, if not impossible. Red dots are also more fragile than iron sights. They can get knocked loose, get dented in a fall or accident, or stop working for some mysterious electronic reason. In any of those situations, a suitable set of back-up iron sights will be helpful.

How they Shoot

The proof of the pudding is in the eating, or in this case, in the shooting. The sights shot low, but that is to be expected as I was on our pistol range shooting at about 40 feet and the bullet is still rising. The red dot is sighted in at 36 yards, which keeps the bullet within about two-and-a-half inches from the point of aim. I’ll have to get to the rifle range and do a more thorough test.

An explanation of how AR-15 iron sights and red dots can co-witness.
When you deploy your BUIS when using a red dot optic, you will get the absolute co-witness, seen on the lower left, or the 1/3rd co-witness, seen on the lower right.

One thing I ran into was that the optic was mounted high, giving me a one-third co-witness when I had the sights deployed while using the red dot (see graphic). I prefer using an absolute co-witness. That’s not the fault of the A.R.M.S. sights, however. I need to get a shorter riser. I may even have one in one of my big boxes of stuff. The trick will be finding it.

There’s nothing wrong with a one-third co-witness. Both methods work, so it comes down to personal preference. I learned and trained with an absolute co-witness, and I am afraid that I will position the red dot on the top of the front post, which would send the bullet much too high. For now, the solution is to keep the sights down until the battery dies.

Pros

  • Cost effective compared to all-metal sights and other brands
  • Solid, durable feeling set of sights
  • Quick and easy to deploy
  • Easy to install, requiring only a flat screw driver.
  • Mounting screw came with some kind of thread locker already applied
  • Standard sight picture you should be used to
  • Made in the USA

Cons

  • They are not metal. (For some, polymer body and base may be a concern.)
  • If there is a weak point, it would probably be the clip that holds down the sight.

Rating

Rated 5 out of 5.
Rated 5 out of 5.

While I will continue to use and test these back-up iron sights, I see no problems and would buy them again and recommend them to others.

Product Review: The A.R.M.S. Model 71L Back-Up Iron Sights

Author: The Pickled Prepper

Pete the Pickled Prepper lives on an isolated homestead on the side of a mountain deep in in rural America. He has been preparing for the end of the world for more than 25 years.