Training Replica: FN509 Midside 4"

The FN 509 Midsize is often called the "Glock 19 of the FN world." It was created by taking the 4-inch slide and barrel from the standard FN 509 and pairing it with a shortened "Midsize" frame. This specific combination is designed to provide the sight radius and ballistic performance of a full-size duty gun while featuring a shorter grip that is significantly easier to conceal.

Key Design Elements

• The "Ideal" Proportions: By maintaining the 4.0-inch barrel, FN ensured the pistol remains accurate and easy to shoot, while the shortened frame reduces "printing" (the outline of the gun showing through clothing) during concealed carry.

• 15-Round Standard Capacity: The Midsize frame uses 15-round flush-fit magazines. However, it maintains backward compatibility with the 17-round and 24-round magazines from the full-size 509 (though using these in the Midsize frame usually requires a grip sleeve to fill the gap and prevent over-insertion).

• Improved Trigger Face: When the Midsize was first released, it debuted a flatter-faced trigger compared to the highly curved hinged trigger of the original 509. This design helps the shooter pull the trigger more consistently to the rear.

• Fully Ambidextrous: Like its siblings, it features a dual-sided magazine release and slide stop, making it one of the most "lefty-friendly" midsize pistols on the market.

• Lighter Recoil Spring: FN adjusted the recoil spring weight in the Midsize compared to the early full-size models, making the slide noticeably easier to rack for a wider range of shooters.

Midsize vs. Midsize Tactical (2026 Comparison)

Tactical Specifications

Performance Notes

The 509 Midsize is frequently chosen over the 509 Compact by shooters who want a "full-hand purchase." On the Compact, many shooters' pinky fingers hang off the bottom of the f ush magazine, whereas the Midsize frame allows for a complete, secure grip for almost all hand sizes.

Note for 2026: While the FN Reflex has taken over as FN's primary "micro" carry option, the 509 Midsize remains a top choice for those who prefer the shootability and ruggedness of a larger-chassis striker-fired pistol.