How to Mount a Scope On AR-15 With Front Sight

How To Mount Scope On AR-15 With Front Sight
Alfred Mendoza

It is challenging to improve your long-range shooting skills with a stock scope. Upgrading a scope on your own would help, but the next question would be how to mount a scope on AR-15 with front sight. 

Read more as our team made the process easier to guide you.

1. Gather All the Materials Needed

Before starting the process, prepare the tools you need to mount the scope for your AR-15 with the front sight. A torque wrench and hex bit tool are pretty helpful and handy tools to work with your firearm. Rubbing alcohol and cleaning patches is for cleaning the screws and the rail. 

In case your scope does not come with a mount, you can purchase a separate scope mount. To hold the rifle in place, you will need a gun vise or rest. For a properly leveled scope, you will need a bubble level not to ruin the accuracy.

2. Choose Between Absolute vs ⅓ Co-Witness

The red dots on the optics of AR-15 usually come with a riser height of either absolute or ⅓ co-witness. There are also standard heights of iron sights on most rifles. It is best to choose between co-witnessing and absolute to maximize the usage.  

If you want the front and rear irons aligned with the red dot and match up when flipped up, you may choose an absolute. On the other hand, if you prefer to utilize a rear and front sight that is lower ⅓ of the view and red dot and mil-dot, you may get the ⅓ co-witness.

3. Unload Your AR-15 Rifle

After gathering the materials and choosing between absolute and ⅓ co-witness, the next step is to unload your AR-15. Never work with a loaded firearm. A single bullet of AR-15 is three times faster than a regular handgun bullet and is indeed deadly [1]

After removing the magazine, make sure that the chamber is empty. Check for visible dirt and excess oil. With rubbing alcohol and cleaning patches, clean the screws, rail, and mount.

Unload Your AR-15 Rifle

4. Place the Rifle in a Vice

After cleaning the excess oil and dirt, set your rifle on a gun vice or rest. This position will allow you to put the scope on the firearm in a secured manner. Our team suggests using a vice or rest because it will help test the accuracy once the scope is installed.

With the use of a bubble level, level your weapon and align it vertically on the scope. We want to make sure that when mounting the scope, the firearm is within the level. In addition to this, the use of bubble level will affect the accuracy of the rifle.

5. Install the Scope Mount

After placing the firearm on the gun vice, take the scope mount and place it at the top of the upper receiver. To not cause unwanted stress on the tube, avoid placing the mount on the upper receiver and free-floating rail.  

The next step is to tighten the scope mount to make it stable at the right torque level. Using the torque wrench, tighten it with the recommended tightness. With the use of a torque wrench, you will get to install the mount not too tight.

6. Place the Scope on the Scope Mount

Once the mount is installed, it’s time to fix the scope on your rifle. When placing the optic on the mount, make sure that the rings are on a flat surface. Using the upper rings, secure the scope and tighten it. 

Be reminded not to fully tighten the scope rings unless you look over each side of the two rings. The scope rings should be on the same gap level that allows the user to move the optic. In addition to this, you can check the eye relief to find the position that suits you.

Place the Scope on the Scope Mount

7. Level the Scope

Since the gun is leveled earlier, you will now level the scope with a bubble level. Ensure that the reticle is aligned vertically and horizontally before leveling the scope. With the use of a vertical verified target like a door jamb, align the reticle. 

When you align the crosshair, position the bubble level on the top of the scope. Make sure that the optics are well aligned and will give you accurate shots. You can check if it’s properly aligned once you shoot. 

8. Lap the Rings (Optional)

This step is optional since it’s risky to do it yourself. Lapping is sanding the rings inside to have a precise result. It gives a surface to surface contact between the rings and the optics.

When it comes to the lapping of scope rings, we highly suggest you let the gunsmith do the work. It may need a professional since it may easily ruin the ring. 

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Additional Tips

  • Never skip using a bubble level.
  • When mounting, look at the target through the scope to shoot accurately at a long distance.
  • Tighten, but do not over tighten the sight completely.
  • Gradually adjust after installing the optics when needed. 
  • Low magnification scope means the front sight post may obscure the sight picture. Higher magnifications mean the front sight obstruction may fade, so mounting a scope in free-floating rail is recommendable.


Most scopes on AR-15 with front sight should be mounted as low as possible. Just make sure that any portion of the scope does not touch the barrel or any rifle parts. A higher optic is prone to more force and torque that may result in more recoil when shooting.

Yes, the AR-15 scope mount height matters. The lower the scope, the closer it is to the axis of the bore. More likely, it will give a consistent sight picture and accurate long-distance shooting. In addition to this, a lower mount gives comfort to most shooters.

No. It is unnecessary to unmount. However, iron sights unmounting it is not a crucial step. Remove the screw from the flat part of the upper receiver. Unlike an iron sight, the fixed front sight is complicated because of the gas block, so you may need a gunsmith for that.

So, How Do You Mount AR-15 Scopes with Front Sights?

AR-15 is one famous weapon when it comes to the accurate and sturdy front sight. However, adding a secondary scope on AR-15 would create significant improvement, especially in long-range shooting. 

In our final thoughts, the process when you mount a scope is pretty simple. Just be patient on leveling the scope when mounting. With the right tools, you can mount your gun scope. It will have a positive effect when you mount a scope and can avoid damage. 

Now that we know all the steps on how to mount scope on AR-15 with front sight, the mounting process will be easier.



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