Herrington Arms
FN 509 Midsize MRD Compensators
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Manufacturer
FN
Model & version
509 Midsize MRD
Mounting details
MIL-STD-1913 Picatinny, FN Low-Profile Optics Mounting System
Parts listed
3 total
FN 509 Midsize MRDCompensators
What the compatibility labels mean
How we knowHow we check compatibility
- Lab testedFit checked by Firearm Lab for the recorded setup.
- Documented fitmentSupported by manufacturer, partner, or reviewed community evidence.
- Interface matchMounting details match, but this exact model and part have not been confirmed to fit together.
Check your exact model and part before ordering. Fitment limits
Herrington Arms1
Based on manufacturer information — Aug 2026. May require modification — see notes.
Parker Mountain Machine2
PMM Duty Compensator for FN 509
May require modification — see notes.
PMM Ultra Compensator for FN 509
May require modification — see notes.