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Mounting Scope on AR 15 with Iron Sights: A Complete Guide

Mounting Scope on AR 15 with Iron Sights

If you’re still wondering whether you should take your firearm to a professional gunsmith or just do everything by yourself, this is your sign to do it.

Installing a scope on your arms with a front sight is SIMPLE and EASY, and you’ll only need a few tools.

Let’s get started on the AR 15-with-front-sight installation guide!

Tools You’ll Need

Like any DIY project, this mounting process will be a lot easier if you have the right tools. Start by gathering these first:

  • A flat surface to work on
  • Torque wrench
  • Bubble level
  • A cleaning vise or universal level to hold the gun while you work
  • Hex bit tool in case you overtighten

How to Mount Scope on AR 15 with Iron Sights: 8 Steps

Female soldier

After you’ve gathered all the tools, it’s time to go through all the steps!

Step 1: Unload Your AR 15 Rifle

Before anything else, don’t forget the most crucial step of UNLOADING your gun first. You don’t want to encounter any accidents while working!

When I was still starting out, this step almost slipped my mind. Who knows what might’ve happened!

Remove the magazine and empty the chamber.

Additionally, find a clear, clutter-free workstation. Find a flat surface to work on and place your rifle and other equipment on it.

Step 2: Clean Your AR 15 Gun

It’s easiest to work with a CLEAN gun. With the dirt and oil removed, your hands won’t slip while working.

To clean, take some rubbing alcohol and an old cleaning cloth. Clean everything on your gun, from the rail to the mount.

I always use a microfiber cloth, as any other cloth may cause scratches.

Step 3: Detach the Sights

To make things easier, detach the rear sight and front sight before you mount it.

The rear iron of your AR 15 with front sight is the easiest to detach, so I would uninstall that first by unscrewing the flat part from the upper receiver.

Your AR 15 with front sight will need MORE CARE when detaching, so check if it is attached to the block first.

If you’re using a flip-up front sight, simply flip it down to install the scope.

The riser height of the red dots on optics is usually either absolute or 1/3 co-witness, while most firearms use standard heights.

Check out my guide to see the best iron sights for your AR-15!

Step 4: Mounting Your Weapon on the Vice

Grab your bubble level for the next step.

Start by taking your rifle and leveling it on your gun vice with a bubble level.

While you’re at it, check the handguard too. It should be properly leveled before you start.

I learned that mounting it on the gun vise keeps it STABLE and helps me check my accuracy later.

Grab the scope mount and place it on top of the upper receiver.

AVOID placing the mount on BOTH the free-floating rail and upper receiver because this will cause unwanted stress on the tube.

Step 5: Install the Mount Scope on the Rail

Take the scope rings loose and have the scope mount facing in the SAME direction as the AR 15 rifle.

Take the scope rings off, then place the scope mount on top of your AR 15 rifle.

Step 6: Position Your Mount Scope

Most scopes will move forward when you’re using your rifle, and it recoils. Load the scope mount forward until you hear it click.

Take your torque wrench with the right tip and slightly torque it down. DON’T do the final torque yet, not until the scope on AR 15 is in place.

After that, continue and do a crosshatch pattern on the rest of the screws.

I recommend an 18-inch pound torque setting for this to avoid damaging your AR 15 scope and scope mount.

NOTE: Be careful not to over-torque the scope mount and scope rings!

Step 7: Mounting Your Red Dot Optics

Pull the caps off your scope and set the scope where you want it.

Position the scope rings on your red dot scope mount.

When mounting the red dot scope, secure the same gap level on the two rings when you torque.

Place the scope in the bottom rings, followed by the upper rings. If you’re co-witnessing, look at where the reticle is in relation to the irons.

When you’re satisfied with your scope placement, you can now tighten the mount at the right torque level. 

TAKE NOTE: While you tighten, keep surface to surface contact around the entire scope.

Check the eye relief to see if you’ve got the sights. If you overtighten while you torque, the hex bit tool can help you fix it.

Step 8: Level the Scope on AR 15

Check if the reticle is aligned vertically and horizontally by using a fixed target as a reference.

Check if the crosshairs are properly aligned too.

Level the scope using the bubble level again. Make sure it’s properly leveled before you proceed!

Are your red dots aligned vertically when you shoot?

If you’re able to shoot accurately, you’re all set!

That’s all! Pretty simple right?

If you also want to have the rings of your scope lapped, I suggest you have a professional do it.

I was tempted to do it myself for that surface-to-surface contact between the rings and scope optics, but it was too risky damaging the rings in the process.

How Far Back Should a Rifle Scope Be Mounted?

Your scope should be mounted as far from your face as possible, BUT BEFORE you see the dark halo around the outside edge of your sight picture.

Also, you shouldn’t have to pull your head back to see your sight completely. The scope on AR 15 shouldn’t hit your nose or dig into your brow either.

If it is, the scope is too far back.

Do Scopes Fit All Rifles?


Scopes are basically universal. Any scope will mount on any AR 15 rifle, handgun, shotgun — basically ANY caliber of guns.

You just need the right mounting compatibility to make it work.

How to Choose the Right Scope for Your AR 15

Soldier shooting rifle

#1 Reticle

When you look through the front sight of your weapon…

Do you prefer a mil-dot or crosshairs? Which reticle makes the zeroing process easier for you?

These are just some questions you need to ask yourself to know what kind of reticle suits your needs best.

I personally like using a Duplex reticle since it is simple to use and doesn’t really have a complex design.

#2 Diameter

The BIGGER your diameter is, the MORE light you see. This also means a clearer image and better accuracy.

However, the catch is the heavier your arms will also be.

Bigger diameter sizes are recommended for a weapon used for long-range shooting.

#3 Lens Coating

The lens coating is how many times your lenses are coated and how many lenses you want to be coated.

The MORE layers of coating there are in total, the LESS glare and more improved vision.

#4 Magnification

What kind of magnification scope do you want? From what distance will you be shooting?

The magnification is for how many times the target is enlarged. A low magnification scope means your targets are magnified only a few times.

To put things in perspective, a 10x magnification scope enlarges your target 10 times, which is great for about 250 to 300 yards.

Similarly, a 4x magnification scope will enlarge your target 4 times.

For long-range shooting, getting scopes great for 500 yards or more is important for the best performance.

If you’re more of a long-range shooter, you’ll want HIGHER magnifications for more clarity.

You could also get a variable magnification scope to fit your different shooting preferences.

To give you some more ideas, I’ve compiled a list of the best AR 15 scopes under 100!

Frequently Asked Questions

Military man

Can You Mount a Scope on AR 15 with Front Sight?

You CAN mount a scope on AR 15 with a front sight.

But having a low magnification scope means the front sight post could block the sight picture. 

Meanwhile, higher magnifications may result in this front sight post not getting in the way of your vision.

I recommend installing a scope on a free-floating rail.

You could also get a gas block WITHOUT a fixed front sight and use that instead of an AR 15 with a front sight and gas block combo to positively affect your shooting.

Does Scope Mount Height Matter?


You want your scope to be as low as it can be. The higher it is, the farther away from the bore.

The lower it is mounted, the easier and quicker it is to spot your targets. It will also give a positive effect on shooting accuracy.

You also want to ensure that the scope doesn’t touch the barrel.

Can You Use an Iron Sight with a Red Dot?

Not really.

The red dot blocks most low-profile irons because they are too small and can’t actually co-witness.

In my experience, being unable to co-witness with your irons is just distracting.

Installing it behind optics will also be useless since the front sight wouldn’t be seen through.

What is Lapping the Scope Rings?

Lapping the scope rings is sanding them down so they are even to give you optimal surface-to-surface contact.

However, I would leave it to a professional to do this to prevent any mishaps.


And you’re done! I hope you found all the steps easy.

All you need is your firearm, the scope and mounts, torque wrench, vise, and bubble level.

This scope + front sight project is quick and effortless, too — you need the right tools and enough patience for the job.

FINAL TIP: If you’re looking for a different solution to your sighting needs, you may want to consider getting ACOG sights for versatile performance.

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