FN 509 Midsize Tactical 9mm 4.5-inch Threaded

About this product

The FN 509 Midsize Tactical is a 9mm striker-fired duty pistol specifically engineered with a 4.5-inch threaded barrel and an FN low-profile optics mounting system for suppressor and red-dot compatibility. This configuration directly addresses the growing demand for a single, adaptable platform bridging the gap between concealed carry and full-size duty/competition handguns. It represents a calculated move by FN Herstal to capture the serious end-user market that prioritizes modularity and NFA-item integration over pure concealment or minimum size.

What is the FN 509 Midsize Tactical used for?

The FN 509 Midsize Tactical is used as a multi-role pistol for armed professionals, home defenders, and shooters operating under Title II regulations. Its primary application is as a suppressor or compensator host for home defense or training, where the 4.5-inch barrel optimizes 9mm terminal ballistics and the threaded 1/2x28 muzzle provides direct accessory attachment. The included suppressor-height night sights and optics-ready slide make it immediately functional with modern red-dot optics, eliminating the need for expensive aftermarket milling.

How does the FN 509 Midsize Tactical compare to the Glock 19X MOS?

The FN 509 Midsize Tactical offers superior out-of-the-box readiness for suppressor use compared to the Glock 19X MOS. While both are optics-ready, polymer-framed 9mm pistols, the FN ships with suppressor-height night sights and a 4.5-inch threaded barrel; the Glock 19X MOS requires an aftermarket threaded barrel and taller sights, adding approximately $200-$300 to its initial cost. The FN's trigger break is crisper at 5.5 lbs versus the Glock's typical 6.5-lb spongier pull, a tangible difference in rapid-fire control, though the FN's frame texture is more aggressive and may chafe during extended concealed carry.

What does it weigh and what are the dimensions?

The FN 509 Midsize Tactical weighs 27.1 ounces unloaded with a flush-fit magazine, a full 2.4 ounces heavier than a standard Glock 19 due to its robust steel slide and longer 4.5-inch barrel. Its overall length is 7.8 inches, height is 5.6 inches with the flush magazine, and width is 1.35 inches at the widest point of the slide—dimensions that place it firmly between a compact carry gun and a full-size duty pistol. This size makes it a viable, if bulky, choice for appendix carry, where the added barrel length can actually aid in concealment by reducing printing grip tilt.

Who is this NOT for?

This pistol is not for the first-time buyer seeking a basic home defense or concealed carry handgun on a tight budget, nor for the shooter who dislikes aggressive frame texturing. The $784 price point, aggressive grip texture, and focus on threaded/NFA applications make it over-specified and potentially uncomfortable for casual use. If your sole purpose is deep concealment in an office environment, a true subcompact like a SIG P365 is a more practical choice, detailed in our discussion of platform-specific fitment considerations.

What's in the box?

The factory box includes the pistol with its 4.5-inch threaded barrel installed, two 15-round magazines, suppressor-height 3-dot night sights pre-zeroed at 25 yards, a cable lock, and all required paperwork. Conspicuously absent is a thread protector for the 1/2x28 barrel threads; FN expects you to immediately attach a muzzle device or suppressor, which is an oversight for storage or transport. The optics mounting plates are sold separately by FN, a common but frustrating industry practice that adds $40-$70 and a 7-10 day wait before you can mount an optic.

Is the FN 509 Midsize Tactical worth it at $784?

At $784, the FN 509 Midsize Tactical is worth the premium if you specifically need a suppressor-ready, optics-capable duty pistol without aftermarket modifications. The value proposition collapses if you do not intend to use a red-dot or suppressor, as you are paying for unutilized features. For a shooter planning NFA integrations, this package saves roughly $350 in aftermarket barrel, sight, and milling work compared to adapting a standard model, making it a financially sound one-stop solution, similar to the integrated design philosophy behind our reviewed Stevens 555 Sporting O/U.