How to sight in a red dot (AR-15 edition)

You’re going to spiral down an expensive rabbit hole of gear, parts, and equipment after purchasing your first AR-15. It may have come with MAGPUL backup sights, iron sights, scope, or a red dot. Today we’re going to explain our proven best method for sighting in a red dot. We’ll use the Sig Sauer ROMEO5 2 MOA Red Dot for demonstration purposes.

How to sight in a red dot and get your zero

A lot of people suggest an arbitrary number when deciding where to zero their rifle at. If memory serves me right, we signed in our rifles at 300 yards in the Marines (iron sights). However this may not work for your. We suggest you consider your AR-15’s application or use before assigning or attempting a zero.

Learn the available AR15 platforms here to get your shots out to 300 or 500 yards.

What’s your application?

Thunder Ranch is a big supporter for using a carbine as your primary home defense too. Do you have 300 yards in your house to protect? Are you going to the range and shooting at a distance of 50 yards tops? Or are you MILSIM’ing by sneaking up on your target from 500 yards away (we hope not)?

Choose the yardage that’s best for your application. We also suggest that once you choose your zero and are zeroed, see what the rifle does at different yardages so you can adjust if necessary (i.e. – having a 100 yard zero but using a rifle in self defense at 25 yards).

Read: The Best Beginner AR-15 Rifle

What is MOA and how does it affect my red dot?

Minutes of Angle (or MOA) for red dots refers to how large (in inches) the red dot is at 100 yards. For example – a 2 MOA red dot will cover a 2 inch target at 100 yards. A 6 MOA red dot will cover a 6 inch target at 100 yards.

Why does MOA matter?

MOA matters when considering your application. If you’re shooting longer distances, you’ll probably want a smaller red dot (a pinpoint on a target is better than a blob covering the entire target, agreed?). If you’re getting up close and personal with your target, a larger red dot (i.e. – 6 MOA) would mean faster target acquisition and a faster response to that timer or intruder.

How do I sight in my AR-15 red dot?

Here’s how we have sighted in our scopes and red dots:

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