5 Best Red Dot Sights For FN 509

This guide features 5 best red dot sights for FN 509.  Handgun shooters trust these products for years, and they're great for both range training and daily concealed carry.

More red dot sights are coming out with new technology. Some cost a lot, while others are priced just right and still offer good quality.

Buying expensive red dot sights for FN 509 doesn't mean it's great, so this list include red dot sights at all price points.

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Best FN 509 Red Dot Sights

Holosun 507C - Best Overall

holosun 507c

The Holosun 507C fits right into the RMR optic cut on the FN 509, so you don't need any extra pieces. One of the best parts is its big buttons. They're simple to use, even if you have big fingers, and you can see them in the dark.

The battery can work for up to 50,000 hours. And if it stops, there's a solar panel that keeps the sight going. You can switch out the battery easily from the side without having to remove the whole sight. Even if the battery stops, the sight won't turn off because of the solar backup. Right now, it's a great deal, making it as good of a choice as the Trijicon RMR.


  • Affordable
  • Very long battery
  • Side loading battery
  • RMR footprint


  • Turret requires a very small tool to adjust

Holosun 509T - Best Weatherproof

holosun 509T

The Holosun 509T can handle any weather. It keeps out dirt, water, and other things you don't want interfering with the emitter screen. You can easily put this strong optic on any platform by using a RMR to 509T conversion mounting plate. 

The CHPWS plate can mount the Holosun 509T on the FN 509.


  • Full weatherproof
  • Side loading battery
  • RMR footprint


  • Solar feature only works under strong ambient light

Trijicon SRO - Largest Sight Window

trijicon sro

The Trijicon SRO 5 MOA is perfect for competitive shooting and getting on target quickly especially with a longer sight radius. The SRO uses the same RMR base and has an impressive battery life that last more than 4 years, though it's not meant for heavy-duty use in the context of direct impact on the lens repeatedly.

With this sight, you can spot the dot faster and more reliably, even if your pistol draw is a bit off. It also offers automatic brightness settings. You can pick a brightness level and lock it, or let the surrounding light decide for you. A great feature is the top battery compartment.

You can change the battery from the top without removing the sight or resetting it. After each shot, you can spot the dot again quickly, so you don't waste time searching for it. Some people think you need to remove the sight to change the battery, With the SRO, battery changes are hassle-free right from the top without sight removal.


  • Large sight window 
  • Easier dot tracking
  • Faster sight acquisition


  • Lens not duty grade like the RMR
  • 6.5 MOA not offered, but a weird 5 MOA is
  • Turret clicks not audiable

Trijicon RMR Type 2 - Best Durability

trijicon rmr type 2 led

The Trijicon RMR Type 2 is the best RMR alternative for many years. It's designed with a better battery grip, ensuring the dot stays on without any hitches. This red dot sight is made from the super tough 7075 T6 aluminum material, so it can handle drops and other rough handling without breaking.

The Lock Mode on the Trijicon RMR automatically sets the brightness, making it great for concealed carry. It also has two modes that work well with night vision goggles. Its battery can last up to four years, but you should change it yearly. It offers red dot sizes from 1 MOA to 6.5 MOA.

For those with astigmatism, the 6.5 MOA dot is the best pick. Some people might think bigger dots are not precise, but in reality, the 6.5 MOA dot ensures faster target acquisition and a rounder dot.


  • The most durable on the market
  • Lens shape divert impact stress away from the glass
  • Very long battery life


  • Bottom battery loading
  • Not weatherproof

Trijicon RMR HD - 3rd Gen RMR

trijicon rmr HD

The Trijicon RMR HD has a big window, similar to the Trijicon SRO but featuring the original RMR durability that everyone has been begging to design.

This optic also has a special sensor in the front. This sensor changes the brightness of the dot based on the light around your target. So, if you're using a pistol light or if it's really sunny, the dot will always have the right brightness for shooting.

Ultimately, this is bridging the gap between the SRO and the RMR type 2.


  • SRO meeting RMR 
  • Auto brightness adjustment based on target brightness
  • Top loading battery door
  • Very long battery life


  • Overhangs may cause malfunction
  • Not weatherproof

Swampfox Justice - Best For The Money

swampfox liberty red dot sight

Most red dot sights differ from the Swampfox Justice red dot sight. The Swampfox Justice fits perfectly on any RMR optic cut slide because it uses the same RMR footprint. Its unique tapered sight design (1 X 27) makes the field of view seem larger, helping users quickly lock onto targets.

The Justice from Swampfox has a clearer sight picture compared to the Liberty. Like other red dot sights, it gives unlimited eye relief for fast target spotting. Its lightweight, skeletonized body fits most optic-ready holsters, including the ALS series duty holsters. A unique feature of the Justice is its "Shake Awake" technology, which is like the motion sensor in the Holosun 507C.


  • Unique sight window design
  • Top loading battery access
  • Responsive buttons


  • Tapered sight window still not big enough

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