A Guide to Iron Sights

Posted by Patrick "BabyfaceP" James on June 11, 2021
A guide to iron sights

Iron sights have been around as long as powder-actuated weapons and are intuitive to the human brain, yet some new shooters will no doubt have questions on how they developed in recent history and what you should use. The focus of this will be around rifle use, specifically modern sporting rifles, i.e. AR-15 rifles.

What Are Iron Sights?

Iron sights come in many different forms for many different weapons, but, for our discussion on the AR, they are the sighting method originally used on the Armalite family of rifles, with many folks now running fold-down backup irons in case of optics failures. 

Carry Handle Irons

Historically the AR15/M16 family of rifles used a carry handle style of iron sight. On the original M16 fielded in 1964 moving all of the way through to the M16a2 fielded in 1982, a non-detachable carry handle style sight was the norm. During the Vietnam era this would have been the style of sight used. Below is what they would have seen when looking down range for target acquisition. 

The carry handle was an integral part of the upper receiver and thus couldn’t be removed or swapped. This made for a great, rigid, unyielding rear sight that was hard to break with very few failure points. 

With the adoption of the M4 in 1993 and the M16a4 in 1997 came the flat top upper with a removable carry handle. These are bolt-on Picatinny carry handles that can be removed and replaced with more modern Picatinny railed optics, those being a story for another day. The carry handle is aesthetically great plus durable and battle-tested if just a little slower than a red dot when it comes to target acquisition.

A1/A2 Front Sight

The other half of the AR15/M16 iron sight equation is the front sight. Historically for standard rifles, your front sight tower was pinned in place to make it bomb-proof, and they truly are. Pinned-on front sight towers are rugged things and can take a lot of abuse. The problem many shooters find with permanently attached front sight towers is that they obscure the lower part of your optic when aiming which is why many shooters today are moving to flip-up iron sights, which we’ll get to further in the article. If you have a fixed front sight, it can be removed and replaced with some effort and the proper armorer tools in your garage. Any local gunsmith shouldn’t have trouble removing a pinned on sight.

Flip Up Iron Sights

Most modern shooters will be looking for flip-up iron sights, aka backup iron sights or folding sights. These types of sights are typically attached to the upper receiver and front of the rail. The major benefit is that they fold out of the way of your scope or red dot giving you a clearer view of your target. They are also there if the worst were to happen and your red dot was to go down while your rifle is actively being used. On some models, all it takes is a quick button press and you’re back in the fight. And of course, irons tend to be less expensive than nice optics which means that while you are saving those pennies for the optic of your dreams, you can still be out getting trigger time and practicing.

Fixed Front Sight Post 

So your rifle already has a fixed front sight post. Great! That means you don’t need to buy a folding front sight which means more money for ammo and training.

Let’s discuss how to use, install, aim, and sight-in. Due to your existing fixed front sight post, all you need to do is settle on a rear sight, either fixed or folding, and learn to use it. You can pick up a carry handle and go old school, or a folder for when you move up to an optic. In either case, you’ll need to attach your rear sight to your AR upper receiver. You will want your rear sight pushed as far back as possible on your upper. The further the distance between your front and rear sight the better because it helps improve accuracy. When you install the sight make sure to use a little thread locker and tension it down so it won’t loosen up.

Irons have been made to work with the human brain so don’t overthink aiming. Get behind your rifle, center the front post inside the rear ring and squeeze the trigger; Your brain is designed to want to center objects so let nature work. With a properly sighted rifle, whatever is sitting just on top of the front post when it’s centered in the rear sight will now have a hole in it. “But how do you get it sighted in?” you may be wondering.

 Let’s cover the two main principles of optic sight in:

  • Elevation - (how high or low the bullet strikes) is set by raising or lowering the front sight post. 
  • Windage - (how far left or right the bullet strikes) is set by moving your rear sight left to right.

Elevation is opposite to what you might think. Raising the front sight will move your bullet impact down, lowering the front sight will bring the impact point up. Remember that, want to shoot lower, RAISE your front sight, want to shoot higher, LOWER your front sight.

When it comes to windage, they move in the same direction. If you want your bullet to hit further left, move your rear sight to the left, if you want it to hit further right, move it to the right. And with all things, take your time as you sight in your irons; It’s part of the fun.

My personal opinion here is to zero your iron sights at approximately 25 yards and have it so whatever is sitting on top of the front post when the trigger is pulled is where the bullet goes.

Railed Sights

If your rifle doesn’t have a front sight post but does have a nice Picatinny rail you’ll need to pick up both a front and rear sight. Same as before, the rear sight should sit as far rearward as possible on the upper receiver. Your front sight needs to be pushed as far out on the rail as possible; This is why having a quality rail is important, you don’t want it to loosen or move under stress.

The same sighting fundamentals apply to MOST flip up irons, the front controls the elevation while the rear controls the windage. 

Plastic vs Metal Iron Sights

The plastic irons such as Magpul flip-ups will work for most situations and hold up to wear and tear just fine while also being lighter (top image).

Aluminum and steel sights are a step up in durability and weight (bottom image). 

The only time you don’t want to run plastic irons is if you are mounting the front sight to a railed gas block as it can melt the sight with enough shooting. If this is you, you need metal.

Red Dot Co-Witness

There are two main co-witnesses that people discuss, absolute and lower 1/3.

Absolute co-witness, pictured directly above, means that your back up iron sights will center perfectly in your red dot. The benefit here is that when you flip them up, you don’t need to move your head from it’s normal shooting position to get your irons in play, they will be looking straight through the middle of your dot.

Pictured above, lower 1/3 sits with your red dot slightly higher which places your iron sights in the lower 1/3 of your optic. The benefit to a lower 1/3 co-witness is that it brings your head up higher to what some consider to be a more natural shooting position. If your red dot goes down, you need to move your head down slightly to get your irons on target. 

One co-witness is not better than the other, they work well for different users depending on how you shoot. Try both and see what your eyes and brain like best. Oh, and don’t be afraid to change later on if you find something else working better for you.

Patrick "BabyfaceP" James is a garage gunsmith who loves anything mechanical. His motto is "With enough time and patience we can build anything and together we are learning the best way to build all things gun related."

James Harless
1 month ago at 5:13 PM
Excellent discussion. I think even the most seasoned veteran would enjoy reading.
Randolph Vigallon
1 month ago at 5:02 PM
Another well written and informative piece of information. Thanks!
1 month ago at 10:13 PM
Steve Sweet
1 month ago at 10:52 PM
Love the information . Going to stay with the iron sights for a while. Always liked them on the m16 in the Army . Thanks
1 month ago at 11:34 AM
Good article. This is not a criticism, but a comment, instead. A new shooter may have problems with a new BUIS rear sight, especially if he is removing a carry handle sight system, but has a fixed front sight. Most BUIS do not have the ability to adjust elevation which means, of course, that adjusting the front sight post can be a big problem for someone who did not buy a sight adjustment tool when they bought their rifle. Not a problem for the retired Marine Gunny Sgt, but might be tough to do for a newbie with the tool. I have taught over 3000 M-1 Garand shooters how to adjust their sights and have used an easy to remember acronym. FORS means Front Opposite, Rear Same when adjusting the sights in relation to the point of impact. Keep up the good work.
1 month ago at 11:34 AM
I love that acronym!!! Thank you!
David Walters
1 month ago at 1:38 PM
What? No coverage of offset iron / plastic sights?
Michael Anthony
1 month ago at 4:16 PM
???? great read! i love iron sights.
Garth Dalson owner of Infidel Tactical USA
1 month ago at 5:06 PM
Nice article Patrick. Were you in the military? To be honest I can not remember if I used the absolute co-witness or the lower 1/3 co-witness while in the military. In basic training this was never discussed, but while I got to my active duty unit it was discussed. We issued red dots to everyone in the platoon except squad leaders and NCO's, then once I became a squad leader (at exactly my 2 year mark I became my squad leaders, squad leader lol) and was issued an ACOG. I preferred the ACOG in Iraq, except while kicking in doors but rather than take the ACOG off or mount a quick reflexive sight I just used my front sight post which gave me quick target acquisition. Red dots were not all that popular in my Infantry unit, as years progressed and i became an E5P everyone was issued ACOGS by that point. I broke down and bought a few red dots over the last year and a half, they are cheap and allow a cheap option for fairly easy target acquisition. Once they came out with the 3x magnifiers you could have the best of both worlds ( minus the quick range detection the ACOG gives you). With these "new" magnifiers you can have the 3x of the ACOG and the quick target acquisition of the red dot. Of course, I still prefer the ACOG with the small reflexive fire optic mounted on top. Nothing IMO, right now at least, beats the optics and easy range finding from an ACOG. All of my friends who were not in the military have no understanding of the real benefits of the ACOG because they don't understand how the optic works. I will be posting a blog once my stores website is finished being created. If you want, send me your resume & I wouldn't mind having you write a blog on my page here and there.
Tom Blue
1 month ago at 9:39 PM
Great article
gregory rivers
1 month ago at 6:32 PM
nice article, even though i've used iron sights most of my life and still prefer them most of the time.
1 month ago at 7:55 AM
Well written. Since I have been shooting for more years than I like to admit I learned only one thing: the part about the railed gas block and plastic (Magpul) melting sights. I thought they were made from a high carbon fiber content polymer that can withstand high heat.
1 month ago at 1:06 PM
Nice article, short and sweet.
William Raley
1 month ago at 1:21 PM
Very useful information. As a new shooter I need to gather as much information as possible to better make decisions, and save money. Thanks again for providing this information.
Gerald Harvey
1 month ago at 6:29 PM
Great post. BabyfaceP 2024!
1 month ago at 7:40 AM
Nice article and spot on for me. I trained "iron" never having the advantage of optics so keep one weapon that is "basic" with exception of tritium sights installed. My son is a Marine and keeps optics up on his weapon of choice. He "schooled" me on Co-witness and prefers lower 1/3.
Vic P
1 month ago at 2:11 PM
Great information! Keep educational info coming for us shooters!
Bruce Krocza
1 month ago at 3:18 PM
Great article and very informative. After reading this I had a better appreciation for my fixed front site and the magpul rear that I installed.
1 month ago at 5:24 PM
Is it better to zero in at twenty-five yards or thirty-six yards. I've heard both but would like ur opinion or should do it at hundred yrds as this might be my average shooting distance?
1 month ago at 10:36 AM
Ira, if you are going to be consistently shooting at 100, I would sight it in at 100. If the distance you are going to shoot at varies, I personally like 25, but there is nothing wrong with 36.
Brent Copeland
1 month ago at 8:18 PM
What about a 1.93 mount? Why would/wouldn't you choose this?
1 month ago at 10:43 AM
Brent, we know that general consensus states that 1.93 is not good for prone, but more suited for run and gun. It really is personal preference.
LTC Steve Bullock, AUS (Retired)
1 month ago at 8:31 PM
Good data, good photos, good writing. I do believe you now need to talk about sight picture. You talked all around it and showed the example, but for iron sights, it’s all about sight picture. You can hold your breath til you’re blue, squint and do whatever rain dance suits you, but if the barrel is not pointed at the target when you squeeze the trigger, you will miss. In 24 years with the USA, Field Artillery, I rarely found a new soldier who knew what a good sight picture was. The 1/2 hour they teach on it in Basic is easily forgotten, but sooo important. Since it appears your current article was mostly well received, you may want to follow-up with “sight picture”, why it’s important and how to do it with irons. When it really counts, there are few do-overs.
Pomerantz Harriet
1 month ago at 4:02 PM
Need from sight for colt commander 1911, what should it cost and where can I have it done? Could mail slide.
1 month ago at 10:22 AM
Hi Harriet. Unfortunately we do not do any custom work. I would suggest checking in your area for a licensed gunsmith who can help you out.
Roger Risch
1 month ago at 12:14 PM
A lot of rifles have a picatinny gas block that is a quarter inch lower than the receiver rail. Is there a solution to this other than getting a rail height gas block and swapping it out?
1 month ago at 11:17 AM
Roger, you do not have to swap it out. I would just get a .25" Pic Riser for it. This is a simple fix that is easy and will save you plenty of time and money.
1 month ago at 8:59 PM
Great article, clear, concise and on point!