FN 509M NMS 9mm | 4″ Barrel | MFG# 66-100464

The FN 509 Midsize (509M) is a 9mm midsize pistol featuring a 4″ cold hammer-forged barrel, fixed 3-dot luminescent sights, and a black polymer frame with interchangeable backstraps. It ships with two 10-round magazines and a matte black slide with front and rear serrations for positive manipulation. For shooters seeking a red-dot option under $1,000, a compact optic such as the Holosun 507C or Trijicon SRO pairs well with a 4″ slide and maintains a low profile for everyday carry and range use.

Suggested uses include everyday carry (EDC) and range training/target work where a midsize platform balances shootability and concealability. The included backstraps and ambidextrous controls allow users to fine-tune fit and handling for consistent performance in those roles.

Product Specifications

• The manufacturer is FN America / FN Herstal.
• The model is listed as FN 509 Midsize (509M).
• The manufacturer’s part number is 66-100464.
• The UPC is 845737010027.
• The caliber is 9mm.
• The barrel measures 4 inches and is cold hammer-forged with a recessed target crown.
• The sights are Fixed 3-Dot Luminescent.
• The firearm ships with 2 magazines.
• The magazine capacity is 10 rounds.
• The frame material is Polymer.
• The frame finish is Black.
• The slide is described as Black Steel with improved front and rear cocking serrations.
• The grip uses Black interchangeable backstraps to alter fit.
• The overall length is listed as 7.40 inches.
• The weight is listed as 26.50 oz.

The FN 509 Midsize offers a balanced blend of features aimed at users who want a controllable, compact 9mm platform that retains full-size ergonomics. Its cold hammer-forged barrel and three-dot luminescent sights provide a solid baseline for accuracy and sight acquisition, while the interchangeable backstraps and included magazines make it ready for immediate use at the range or for daily carry setups. This model’s restrained, functional configuration appeals to shooters who prioritize reliability and ergonomic adaptability without unnecessary extras.

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