Mounting an optic on your AR-15 is one of the most impactful upgrades you can make, dramatically improving your accuracy and target acquisition speed. Yet, a scope that isn’t properly installed can lead to endless frustration, with shots consistently missing their mark no matter how much you adjust the turrets. The process might seem intimidating, full of mysterious tools and precise measurements, but it’s a skill any shooter can master. Getting it right the first time ensures your rifle performs as intended, building confidence with every shot.
This guide will walk you through a straightforward, reliable method for getting your scope range-ready. We’ll demystify the tools and techniques, breaking it down into a series of manageable steps. By following this process for How to Mount a Scope on a AR15 [Quick & Simple Steps], you can avoid common pitfalls and achieve a solid, dependable mount that holds zero shot after shot. Let’s gather what you need and get started.
Gathering Your Tools and Workspace
Before you lay a hand on your rifle, it’s crucial to have everything you need within reach. A clean, organized workspace, like a sturdy bench or table, is your first requirement. You’ll need a set of hex keys or Torx drivers that fit the screws on your scope mount—using the correct size is non-negotiable to avoid stripping the screw heads. A torque screwdriver is highly recommended to apply the precise amount of force specified by the mount and scope manufacturers, preventing damage from over-tightening.
You’ll also need a gun vise or some stable supports to hold your rifle securely without scratching it. Have some isopropyl alcohol and lint-free cloths or swabs on hand for cleaning the mounting surfaces. Finally, don’t forget your scope’s leveling kit, or as a simple alternative, a set of feeler gauges. Having all these items prepared beforehand makes the entire process smooth and stress-free.
How to Mount a Scope on a AR15 [Quick & Simple Steps]
With your tools laid out, it’s time to dive into the actual mounting process. Take your time with each step, as rushing here is the most common cause of errors.
Step 1: Preparing the Mounting Surfaces
Begin by ensuring your rifle is completely unloaded and safe. Remove the upper receiver from the lower if it makes it easier to handle. Take your mount and separate the top and bottom rings if it’s a two-piece design. Thoroughly degrease all the contact points: the picatinny rail on your AR-15’s upper receiver and the base of the scope mount itself. Use isopropyl alcohol and a cloth or swab until the surfaces are completely clean and dry. Any oil or debris left behind can cause the mount to shift under recoil.
Step 2: Setting the Scope in the Rings
Place the bottom half of the scope mount onto the rail and hand-tighten the mounting screws just enough so it doesn’t slide around freely. Now, carefully place your scope into the rings. This is where eye relief comes in. With the rifle shouldered in a natural firing position, slide the scope forward or backward until you have a full, clear sight picture without any dark shadows around the edges. Your eye should be at a comfortable distance from the ocular lens. Once you’ve found the sweet spot, you can lightly tighten the top rings to hold the scope in position for the next critical step.
Step 3: The Crucial Step of Leveling
A canted scope will cause your impacts to drift horizontally as you adjust for elevation. To avoid this, you need to ensure the scope’s reticle is perfectly level with your rifle. Place your rifle in the vise so it’s solid and won’t move. Then, use a small level on a flat part of the upper receiver (like the rail itself) to get the gun level. Now, look through the scope and adjust it until the reticle is also perfectly vertical and horizontal. A leveling kit that attaches to the scope’s turret housing makes this easy. Alternatively, you can use feeler gauges on either side of the scope tube between the rings to ensure it’s sitting evenly before final tightening.
Step 4: Torquing to Specification
This is where your torque screwdriver earns its keep. Following the manufacturer’s instructions for your specific mount, begin tightening the screws in a crisscross pattern, just like you would with a car tire. This ensures even pressure across the scope tube. A common torque specification for scope ring screws is between 15-18 inch-pounds, while the base mount screws that attach to the rail are often torqued to between 30-45 inch-pounds. Always defer to the specific instructions that came with your mount. Over-tightening can crush the scope tube or strip screws, while under-tightening will lead to a loose scope that won’t hold zero.
Final Checks and Heading to the Range
After everything is torqued down, perform a final check. Look through the scope to confirm the reticle is still level and the eye relief is still correct. Give the scope a firm (but not violent) shake with your hands to check for any movement or looseness. If everything feels solid, you’re almost done. The final step is to bore sight the rifle, which can be done with a laser bore sighter or simply by removing the upper receiver’s BCG and visually aligning the barrel’s bore with a distant target through the scope. This will get you on paper at the range, saving time and ammunition.
At the range, you’ll finalize the zero by firing groups and making adjustments to the windage and elevation turrets. Remember that a properly mounted scope is the foundation for all subsequent accuracy. By taking your time and following these steps meticulously, you’ve built that foundation on solid ground, ensuring your AR-15 is ready for any task you ask of it.