FN 509 9mm vs FN 509 Compact 9mm

FN builds the 509 family on the same cold hammer-forged stainless barrel and FNC-coated stainless slide, so material quality is identical across both. The differences are size, capacity, and sights. The full-size 509 carries 17+1 in a 7.4" frame at 26.9 oz with a 4.0" barrel and 3-dot luminescent sights. The 509 Compact carries 15+1 in a 6.8" frame at 25.5 oz with a 3.7" barrel and a hi-viz front sight paired with a low-profile rear. Both run the same 5.5 lb striker trigger, both have MIL-STD-1913 rails, and neither base model has an optic cut.

Pick the FN 509 (full-size) if:

• You want 17+1 over the Compact's 15+1 — 2 extra rounds without giving up the same FNC-coated stainless build
• You want the 5.79" sight radius versus the Compact's 5.6" sight radius for slightly more iron-sight precision at distance
• You want a duty or home-defense gun where the extra 0.6" of length and the 0.3" longer barrel are not concealment liabilities

Pick the FN 509 Compact if:

• You want 0.6" shorter overall length and 0.56" lower height for IWB concealed carry — the Compact carries closer to a Glock 19 footprint than a Glock 17
• You want the hi-viz front sight that picks up faster under stress and in dim light than the standard 3-dot luminescent setup on the full-size 509
• You want a carry gun that still accepts the full-size 509's 17-round and 24-round extended magazines, since FN keeps the magazine platform shared across the family

Both share the same FNC-coated stainless slide, cold hammer-forged stainless barrel, 5.5 lb trigger, and interchangeable backstraps, and both use the same magazine well — full-size mags drop into the Compact and extend below the grip. Neither base model is optic-ready (the 509 Tactical and 509 MRD add that). The choice is capacity and sight radius versus carry footprint and faster front-sight acquisition.