Quick Answer: For most AR-15 owners, the Holosun 510C offers the best balance of features, durability, and value at around $300. If budget is no concern, the Aimpoint PRO or Trijicon MRO are professional-grade options trusted by military and law enforcement.

Our Top Picks at a Glance

What to Look for in an AR-15 Red Dot

Dot Size (MOA)

MOA (Minute of Angle) measures the size of the aiming dot. A 2 MOA dot covers 2 inches at 100 yards. Smaller dots (1-2 MOA) offer precision for target shooting; larger dots (4-6 MOA) are faster to acquire for defensive use. Our recommendation: 2 MOA works for both precision and speed.

Battery Life

Modern red dots run 20,000-50,000+ hours on a single battery—that's 2-5 years of continuous use. Always-on capability means your optic is ready when you need it without fumbling for a power button. Look for common battery types (CR2032, AAA) for easy replacement.

Durability

Your red dot will experience recoil, weather, and abuse. Look for aluminum housings, nitrogen purging (fogproof), waterproof ratings (IPX7 or better), and shock ratings tested to 5.56 NATO recoil or higher. Cheap red dots may lose zero or fail when you need them most.

Mount Height

AR-15s typically use "absolute co-witness" or "lower 1/3 co-witness" mounts. Absolute co-witness aligns the dot with your iron sights when looking through the optic. Lower 1/3 places the dot in the upper portion of the window with irons visible in the lower third. Most shooters prefer lower 1/3 for a less cluttered sight picture.

Open vs. Enclosed Emitter

Open emitter red dots (like the RMR or Holosun 507) expose the LED, making them susceptible to rain, mud, or debris blocking the dot. Enclosed (tube-style) red dots protect the emitter inside a sealed housing. For rifle use, enclosed emitters are more reliable in adverse conditions.

Detailed Reviews

1. Holosun 510C — Best Overall Value

Price: ~$310 | MOA: 2 MOA dot with 65 MOA circle | Battery: 50,000 hours

The Holosun 510C dominates the mid-range red dot market for good reason. The large, open viewing window provides fast target acquisition, and the selectable 2 MOA dot / 65 MOA circle reticle lets you choose precision or speed. Solar backup means the optic works even if your battery dies. Shake-awake technology extends battery life by powering down when motionless and instantly activating when the rifle moves.

Pros: Huge window, solar backup, shake awake, excellent battery life, affordable
Cons: Open top design can collect debris, not as proven as Aimpoint
Best for: Home defense, range use, budget-conscious shooters who want quality

2. Aimpoint PRO (Patrol Rifle Optic) — Best Professional Grade

Price: ~$450 | MOA: 2 MOA | Battery: 30,000 hours (3+ years constant-on)

The Aimpoint PRO is the optic trusted by military and law enforcement worldwide. It's overbuilt, simple, and utterly reliable. The 2 MOA dot is crisp without any starburst or distortion. Night vision compatible settings make it suitable for professional use. The included mount provides a solid, quick-detach option out of the box.

Pros: Legendary durability, proven combat track record, night vision compatible, included QD mount
Cons: No fancy reticle options, smaller window than competitors
Best for: Duty use, home defense, anyone who demands absolute reliability

3. Trijicon MRO (Miniature Rifle Optic) — Best Lightweight Option

Price: ~$400 | MOA: 2 MOA | Battery: 5 years continuous-on

The Trijicon MRO packs a large viewing window into a compact, lightweight package. At just 4.1 oz without mount, it's one of the lightest enclosed emitter optics available. The forgiving eye box makes it easy to get on target quickly. Battery life is exceptional—5 years of constant-on operation from a single CR2032.

Pros: Lightweight, large field of view, American made, exceptional battery life
Cons: Some report slight blue tint on early models (fixed in current production), mount sold separately
Best for: Lightweight builds, competition, shooters who value reduced weight

4. SIG SAUER Romeo5 — Best Budget Option

Price: ~$120 | MOA: 2 MOA | Battery: 50,000 hours

The SIG Romeo5 proves you don't need to spend $400+ for a quality red dot. It includes MOTAC (motion-activated illumination) that turns on when you pick up the rifle and powers off when stationary. The dot is clean, the housing is robust, and it comes with both high and low mounts. For the price, it's hard to beat.

Pros: Incredible value, shake awake, includes two mounts, solid construction
Cons: Smaller window than premium optics, fewer brightness settings
Best for: First AR builds, budget builds, backup optics

5. EOTech EXPS3 — Best Holographic Sight

Price: ~$700 | MOA: 1 MOA dot with 68 MOA ring | Battery: ~600 hours

The EOTech EXPS3 is technically a holographic sight, not a red dot, but it's a top choice for AR-15 owners who want the fastest target acquisition possible. The 68 MOA ring with center dot creates a natural aiming point that draws your eye instantly. Side-mounted buttons clear rail space for magnifiers. Night vision compatible.

Pros: Fastest acquisition, wide field of view, proven military optic, no parallax issues
Cons: Shorter battery life, heavier than comparable red dots, expensive
Best for: CQB, home defense, professionals, shooters who prioritize speed

6. Vortex SPARC AR II — Best Entry-Level

Price: ~$150 | MOA: 2 MOA | Battery: 50,000 hours

The Vortex SPARC AR II offers excellent performance at an entry-level price, backed by Vortex's legendary VIP warranty. The multi-height mount system works on AR-15s and other platforms. It's simple, reliable, and covered by a no-questions-asked lifetime warranty. Perfect for shooters on a budget who want peace of mind.

Pros: VIP warranty, affordable, reliable, included multi-height mount
Cons: Basic feature set, no shake awake
Best for: New shooters, budget builds, backup optics

Full Comparison Table

Frequently Asked Questions

Can I use a pistol red dot on my AR-15?

Technically yes, but it's not ideal. Pistol red dots (like the RMR or Holosun 507C) have smaller windows designed for handguns. They'll work on an AR-15, especially with a magnifier, but you lose the fast acquisition advantage of a full-size rifle red dot. If you want a micro red dot on your AR, consider mounting it as an offset backup sight.

Do I need a magnifier with my red dot?

A magnifier extends your effective range from ~100 yards to 300+ yards by providing 3x-6x magnification. If your AR-15 is primarily for home defense or close-range shooting, you don't need one. If you want versatility for longer shots, a flip-to-side magnifier like the Holosun HM3X or EOTech G33 pairs perfectly with any of our recommended red dots.

Should I buy an American-made or imported red dot?

American-made optics (Trijicon, EOTech, Aimpoint) have longer track records in combat use and are preferred for duty applications. Quality imports (Holosun, SIG, Vortex) have proven reliable for civilian use and offer more features per dollar. For home defense and range use, both categories work well. For professional duty use, stick with proven American or Swedish brands.

How do I zero a red dot on an AR-15?

A 50-yard zero is ideal for most AR-15 uses—the bullet will be approximately 1.5" high at 25 yards, dead-on at 50 yards, and 2" low at 200 yards. Set up a stable rest, fire a 3-shot group at 50 yards, then adjust windage and elevation to move the point of impact to your point of aim. Each click is typically 1 MOA (1 inch at 100 yards, 0.5 inch at 50 yards). Confirm zero with a second group.

Conclusion: Which Red Dot Should You Buy?

• Best for most shooters: Holosun 510C — features, quality, and value in one package
• Best for professionals: Aimpoint PRO — combat-proven reliability
• Best for lightweight builds: Trijicon MRO — minimal weight, maximum performance
• Best for tight budgets: SIG Romeo5 — punches way above its price
• Best for CQB/speed: EOTech EXPS3 — nothing acquires faster
• Best for beginners: Vortex SPARC AR II — quality, warranty, and simplicity

No matter which red dot you choose, you're upgrading from iron sights to faster, more accurate aiming capability. All six options on this list are vetted, reliable, and backed by solid warranties. Pick the one that fits your budget and mission, mount it properly, zero it, and start shooting.

Shop Red Dot Sights at The Armory