{ "apiVersion": 1, "kind": "work-order", "purpose": "Taking the firearm apart for a job such as refinishing, and putting it back together to specification.", "firearm": { "slug": "fn-509", "name": "FN 509", "manufacturer": { "id": "fn-herstal", "name": "FN Herstal" }, "category": "pistol", "action": "striker-fired-short-recoil", "calibers": [ "9x19mm Parabellum" ], "alsoKnownAs": [ "FN 509 Tactical", "FN 509 Compact", "FN 509 MRD" ], "coversAlso": [ "FN 509 Tactical", "FN 509 Compact", "FN 509 LS Edge" ], "page": "firearms/fn-509.html", "bundle": "api/v1/firearms/fn-509.json", "lastUpdated": "2026-10-29" }, "notices": [ "FN Herstal limits owner disassembly: Field strip only: slide, recoil spring assembly and barrel off the frame (striker released); manual also covers magazine and backstrap changes.", "This work order is written for the FN 509. It is reported to cover FN 509 Tactical; FN 509 Compact; FN 509 LS Edge — if the firearm on the bench is one of those, check the torque notes: values do not always carry over." ], "disclaimer": { "headline": "Read this before you use anything here.", "points": [ "This is a guide, not an authority. Entries are compiled from manufacturer manuals, technical manuals, published references, and community knowledge. Some of it comes from sources that are not authoritative, and some of it may simply be wrong.", "Always consult the manufacturer's manual for your specific firearm and serial-number range. Manufacturers change designs mid-production without renaming the model. The manual that shipped with your firearm outranks anything on this site.", "Consult a licensed gunsmith for anything beyond routine field stripping and cleaning, for any firearm you are unsure about, and for any procedure marked as gunsmith-recommended here.", "Treat every firearm as loaded. Verify it is unloaded, with the magazine removed and the chamber physically and visually checked, before any procedure in this database. Point it in a safe direction the entire time.", "Disassembly can damage a firearm or injure you. Springs are under tension, parts can launch, and reassembling a firearm incorrectly can make it unsafe to fire in a way that is not obvious from the outside. If a reassembled firearm does not pass a function check, stop and see a gunsmith.", "Torque values are shown in two groups. Values from the manufacturer or the issuing military are shown as such, with the document they came from. Values reported by anyone else — parts makers, gunsmithing publishers, articles, forums — are shown separately with who said them, how reliable that source is, and their exact words. Those are not specifications. Confirm any torque value with the manufacturer or a licensed gunsmith before relying on it.", "Nothing here is legal advice. Firearms law varies by country, state, and city, and some modifications or configurations are regulated or prohibited. You are responsible for knowing and following the law where you are.", "No warranty of any kind. Contributors and maintainers accept no liability for damage, injury, or loss arising from use of this material." ], "page": "disclaimer.html", "legal": { "summary": "Legal notice: this material is third-party information compiled from sources of varying reliability and is provided for general informational and educational purposes only. It is not gunsmithing, technical, safety or legal advice, it is not verified or endorsed by any manufacturer, and it must not be taken as fact. Any work on a firearm beyond the routine field stripping described in its own owner's manual should be performed only by a licensed and insured gunsmith. You use this material entirely at your own risk. Fundamental Build LLC and the project's contributors make no warranty of any kind and accept no liability for death, injury, damage or loss arising from its use. Full terms: LEGAL.md.", "page": "legal.html", "notice": "https://github.com/Fundamental-build-LLC/Pew-Takedown/blob/main/LEGAL.md" } }, "sourcing": { "confidence": "high", "verification": "manufacturer-manual-verified" }, "manufacturerDisassembly": { "status": "limited", "limit": "Field strip only: slide, recoil spring assembly and barrel off the frame (striker released); manual also covers magazine and backstrap changes.", "statement": "FN says the field strip is enough for thorough cleaning and that disassembly beyond the manual's instructions should only be done by a qualified armorer.", "source": { "title": "FN 509 Owner's Manual (66-100498 R2, 2603)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/wp-content/uploads/2026/03/2603_FN_509-OM_66-100498_R2.pdf", "page": "39", "pdfPage": 21, "pageUrl": "https://fnamerica.com/wp-content/uploads/2026/03/2603_FN_509-OM_66-100498_R2.pdf#page=21", "quote": "This level of disassembly is sufficient to perform a thorough cleaning. Disassembly beyond the instructions provided in this manual should only be carried out by a qualified armorer." } }, "recalls": [], "shopTier": { "tier": 2, "group": "pistol", "rating": "Pew-Takedown editorial rating (1 easy – 3 hardest), not the manufacturer's", "reason": "59 line items in FN's standard-model list (some are day/night, backstrap and magazine variants); FN marks the unlock-block pin, fire-control pin, extractor pin and sights as replace-after-removal, restricts detail work to an armorer, and the manual-safety fire control carries a ball detent and spring. More parts and more traps than a Glock.", "confidence": "medium", "partCount": { "value": 59, "kind": "line-items", "covers": "FN 509 standard model, full-size frame, NMS and MS fire control; the parts list on this page (schematic pp. 58-59, list pp. 60-61); MRD/Tactical slide and Midsize/Compact lists omitted; 59 pieces", "basis": "manufacturer-parts-list", "source": { "title": "FN 509 Owner's Manual", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.wpenginepowered.com/wp-content/uploads/2026/03/2603_FN_509-OM_66-100498_R2.pdf", "page": "60–61", "pdfPage": 32, "pageUrl": "https://fnamerica.wpenginepowered.com/wp-content/uploads/2026/03/2603_FN_509-OM_66-100498_R2.pdf#page=32", "quote": "414 Overmold, Manual Safety" } }, "painPoints": [ { "issue": "Several pins and the sights are single-use per FN: the unlock block retaining pin, fire control pin, extractor pin and front/rear sights carry 'replacement recommended after removal', so a shop needs new ones on hand.", "during": "reassembly", "source": { "title": "FN 509 Owner's Manual (66-100498 R2, 2603)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/wp-content/uploads/2026/03/2603_FN_509-OM_66-100498_R2.pdf", "page": null, "pdfPage": null, "pageUrl": null, "quote": "* Replacement recommended after removal" } }, { "issue": "FN restricts disassembly past the field strip to a qualified armorer.", "during": "both", "source": { "title": "FN 509 Owner's Manual (66-100498 R2, 2603)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/wp-content/uploads/2026/03/2603_FN_509-OM_66-100498_R2.pdf", "page": null, "pdfPage": null, "pageUrl": null, "quote": "Disassembly beyond the instructions provided in this manual should only be carried out by a qualified armorer." } }, { "issue": "Manual-safety models carry a ball bearing and detent spring in the fire control, a captive detent that can fly.", "during": "both", "source": { "title": "FN 509 Owner's Manual (66-100498 R2, 2603)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/wp-content/uploads/2026/03/2603_FN_509-OM_66-100498_R2.pdf", "page": null, "pdfPage": null, "pageUrl": null, "quote": "411*** Spring, Detent" } } ], "minutes": { "strip": 25, "rebuild": 35, "basis": "estimated", "note": "Estimate for an experienced tech with the right tools, detail strip to coatable parts (slide internals, frame pins, trigger group, sights) and rebuild to a function-checked gun; scale used across pistols: Glock-pattern 15/20 min, other strikers 20-30/25-40, DA/SA hammer guns 30-35/45-50, Hi-Power, Colt 1903 and Mark 23 40-45/60-75.", "source": null }, "stripScope": [ { "assembly": "Slide", "removes": [ "slide end cap", "striker, springs, guide and stop pin", "striker block and spring", "extractor, pin and spring", "front sight", "rear sight" ] }, { "assembly": "Barrel", "removes": [ "barrel", "recoil spring assembly" ] }, { "assembly": "Frame", "removes": [ "backstrap and pin", "unlock block retaining pin and unlock block", "trigger pin and trigger assembly", "slide stop lever and spring", "take down lever", "fire control pin and fire control assembly (sear, carrier, springs, pins; ball detent on MS)", "magazine release and spring" ], "tools": [ "punch set", "frame fixture (optional)" ] } ], "hardware": { "pins": 8, "springs": 13, "detents": 2, "basis": "counted from the manufacturer's parts list (one per key number unless a quantity is given)" }, "specialTools": [ { "tool": "Replacement pins kit (unlock block retaining pin, fire control pin, extractor pin)", "usedFor": "FN marks these replace-after-removal" }, { "tool": "Frame fixture / support block (e.g. Apex FN disassembly fixture)", "usedFor": "Driving the forward unlock-block pin without damage" } ], "fitOnRebuild": [ { "check": "Install new pins and sights", "why": "FN marks the pins and sights 'replacement recommended after removal'", "source": { "title": "FN 509 Owner's Manual (66-100498 R2, 2603)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/wp-content/uploads/2026/03/2603_FN_509-OM_66-100498_R2.pdf", "page": null, "pdfPage": null, "pageUrl": null, "quote": "* Replacement recommended after removal" } }, { "check": "Sight position / re-zero", "why": "Drift or pressed sights moved for coating shift point of impact unless witness-marked and returned to the same spot", "source": null }, { "check": "Full function check (trigger reset, safeties, slide lock-back, drop of striker/hammer only on trigger)", "why": "Standard after any fire-control strip; confirms springs and sears went back correctly", "source": null } ], "assessed": "2026-10-29" }, "videos": [], "configurations": [], "tools": [], "phases": [ { "id": "clear", "title": "Clear and make safe", "steps": [ { "n": 1, "instruction": "Point the muzzle in a safe direction and keep your finger off the trigger." }, { "n": 2, "instruction": "Press the magazine release and remove the magazine.", "partsFreed": [ "Magazine" ] }, { "n": 3, "instruction": "Retract the slide fully to eject any chambered round and lock it open." }, { "n": 4, "instruction": "Visually inspect the chamber and magazine well, then physically feel the chamber to confirm it is empty.", "warning": "Look and feel. Both, every time." }, { "n": 5, "instruction": "Remove all live ammunition from the work area." } ], "videos": [] }, { "id": "disassemble", "title": "Disassemble", "videos": [], "procedures": [ { "procedure": "field-strip", "title": "Field Strip", "level": "field-strip", "configuration": false, "steps": [ { "n": 1, "instruction": "Complete the Clear and Make Safe procedure and confirm the chamber is empty. Wear eye protection." }, { "n": 2, "instruction": "Retract the slide and lock it in its rearward position using the slide stop." }, { "n": 3, "instruction": "Remove the magazine and rotate the takedown lever downward." }, { "n": 4, "instruction": "Release the slide stop and ease the slide forward." }, { "n": 5, "instruction": "Keeping the rear of the slide and the rear of the frame in alignment, point the muzzle in a safe direction and press the trigger to release the striker. The slide moves forward slightly as it releases.", "warning": "This pistol requires a trigger press to field strip — the striker has to be released before the slide will come off. Verify the chamber is empty, verify it again, and point the muzzle somewhere a round would not matter before your finger goes near the trigger.", "tip": "FN's manual states the pistol must be completely unloaded to perform this step, and warns that failure to follow it could result in serious injury or death." }, { "n": 6, "instruction": "Pull the slide forward and away from the frame.", "tip": "If the striker was inadvertently recocked, go back and release it again before trying.", "partsFreed": [ "Slide" ] }, { "n": 7, "instruction": "Hold the slide upside down, grasp the small spring of the recoil spring assembly, and lift the assembly up and out of the slide.", "partsFreed": [ "Recoil spring assembly" ] }, { "n": 8, "instruction": "Remove the thread protector or muzzle device if the pistol has a threaded barrel." }, { "n": 9, "instruction": "Grasp the barrel by its lug, lift it up and around the extractor, and slide it rearward out of the slide.", "tip": "Up and around the extractor, then rearward. It does not lift straight out.", "partsFreed": [ "Barrel" ] }, { "n": 10, "instruction": "Stop here. FN states this level of disassembly is sufficient for a thorough cleaning." } ] } ] }, { "id": "refinish", "title": "Refinish", "components": [ { "name": "Slide", "procedure": "field-strip", "level": "field-strip", "step": 6 }, { "name": "Recoil spring assembly", "procedure": "field-strip", "level": "field-strip", "step": 7 }, { "name": "Barrel", "procedure": "field-strip", "level": "field-strip", "step": 9 } ], "manufacturerPartsList": { "parts": 59, "scope": "FN 509 standard model (full-size frame; NMS and MS fire control). Omitted: 509 Tactical/MRD slide assemblies list (pp.64-65) and 509 series Midsize/Compact frame & magazine list (pp.68-69). Schematic pp.58-59." }, "partsDiagrams": [], "materials": [ { "component": "Barrel", "material": "stainless steel", "finish": null, "appliesTo": "FN 509 (standard, 4in), e.g. 66-100002 FN 509 NMS BLK/BLK", "note": null, "source": { "title": "FN 509® — product page (Specs / Primary Features)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/products/pistols/fn-509/", "page": null, "pdfPage": null, "pageUrl": null, "quote": "BARREL … Cold hammer-forged stainless steel" } }, { "component": "Frame", "material": "Polymer", "finish": null, "appliesTo": "FN 509 (standard, 4in), e.g. 66-100002 FN 509 NMS BLK/BLK", "note": null, "source": { "title": "FN 509® — product page (Specs / Primary Features)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/products/pistols/fn-509/", "page": null, "pdfPage": null, "pageUrl": null, "quote": "FRAME … Polymer construction with replaceable steel frame/slide rails" } }, { "component": "Magazine", "material": "polymer", "finish": "black", "appliesTo": "FN 509 (standard, 4in), e.g. 66-100002 FN 509 NMS BLK/BLK", "note": null, "source": { "title": "FN 509® — product page (Specs / Primary Features)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/products/pistols/fn-509/", "page": null, "pdfPage": null, "pageUrl": null, "quote": "MAGAZINE … High visibility, low-friction follower; polymer base with black finish" } } ], "note": "The components the procedures above separate. Coating, masking and cure are outside this database; follow your coating system's instructions. A part the manufacturer marks \"factory fit\" should not be swapped or reworked." }, { "id": "reassemble", "title": "Reassemble", "videos": [], "procedures": [ { "procedure": "reassembly", "title": "Reassembly", "configuration": false, "steps": [ { "n": 1, "instruction": "Fit the barrel back into the slide, reversing the lift-and-around-the-extractor motion." }, { "n": 2, "instruction": "Install the thread protector or muzzle device if the pistol has a threaded barrel." }, { "n": 3, "instruction": "Place the large end of the recoil spring assembly against the recess in the front of the slide, compress it, and slide the back of the recoil spring guide onto the recess until it is centred on the front of the barrel lug." }, { "n": 4, "instruction": "Guide the slide and barrel assembly onto the frame and pull the slide to its rearmost position, locking it with the slide stop." }, { "n": 5, "instruction": "Rotate the takedown lever upward, locking the frame and slide together." }, { "n": 6, "instruction": "Release the slide and let it travel forward, then test the slide stop, trigger, magazine release and manual safety if fitted." } ], "instruction": null } ] }, { "id": "torque", "title": "Torque", "coverage": "sourced", "manufacturer": [ { "fastener": "Optic / slide-cap mounting screws (T10 Torx) through the MRD plate", "appliesTo": "FN Optics Mounting System (\"FN's patented Low Profile Optics Mounting System, U.S. Patent No. 10,352,654\"), the MRD system the FN 509 owner's manual describes in section 11 with the same plates (501-5", "qualifier": "exact", "value": 22, "valueMax": null, "unit": "in-lb", "converted": { "value": { "N-m": 2.5, "in-lb": 22, "ft-lb": 1.8 }, "valueMax": null }, "sequence": "Remove lubrication from screws and holes; o-ring in slide recess; MRD plate over o-ring; optic or slide cap (with MRD insert if required); start both screws; tighten with finger pressure with the T10 wrench.", "threadlocker": "\"DO NOT USE THREADLOCKER.\" (self-locking system)", "source": { "title": "Quick Setup & Reference Guide: FN Optics Mounting System (2603)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/wp-content/uploads/2026/03/2603_Quick_Setup_Reference_Guide_FN_OPTICS_MOUNTING_final.pdf", "page": "PDF p. 1, step 9", "pdfPage": 1, "pageUrl": "https://fnamerica.com/wp-content/uploads/2026/03/2603_Quick_Setup_Reference_Guide_FN_OPTICS_MOUNTING_final.pdf#page=1", "quote": "Start both mounting screws and tighten them down clock-wise with finger pressure with the provided T10 Torx wrench. (Recommended Torque spec: 22 in-lbs)" } } ], "reported": [ { "fastener": "Optic plate to slide screws (6-40 x 5/8 T10)", "appliesTo": "FN 509 series (optics-ready) with Forward Controls Design OPF-FN509T, ACRO plate", "qualifier": "range", "value": 13, "valueMax": 15, "unit": "in-lb", "converted": { "value": { "N-m": 1.5, "in-lb": 13, "ft-lb": 1.1 }, "valueMax": { "N-m": 1.7, "in-lb": 15, "ft-lb": 1.2 } }, "sequence": null, "threadlocker": null, "source": { "title": "OPF-FN509T, ACRO (product page)", "publisher": "Forward Controls Design", "reliability": "secondary", "url": "https://www.forwardcontrolsdesign.com/OPF-FN509T-ACRO_p_517.html", "page": null, "pdfPage": null, "pageUrl": null, "quote": "Torque value for the plate to slide 6-40 x 5/8 T10 screws is 13 to 15 in lbs." } }, { "fastener": "Aimpoint ACRO P1/P2 mounting screw", "appliesTo": "FN 509 series with FCD OPF-FN509T, ACRO plate, Aimpoint ACRO P1/P2", "qualifier": "exact", "value": 26, "valueMax": null, "unit": "in-lb", "converted": { "value": { "N-m": 2.9, "in-lb": 26, "ft-lb": 2.2 }, "valueMax": null }, "sequence": null, "threadlocker": null, "source": { "title": "OPF-FN509T, ACRO (product page)", "publisher": "Forward Controls Design", "reliability": "secondary", "url": "https://www.forwardcontrolsdesign.com/OPF-FN509T-ACRO_p_517.html", "page": null, "pdfPage": null, "pageUrl": null, "quote": "Torque value for Aimpoint P1/P2 is 26 in lbs, and 20 in lbs for Steiner MPS." } }, { "fastener": "Steiner MPS mounting screw", "appliesTo": "FN 509 series with FCD OPF-FN509T, ACRO plate, Steiner MPS", "qualifier": "exact", "value": 20, "valueMax": null, "unit": "in-lb", "converted": { "value": { "N-m": 2.3, "in-lb": 20, "ft-lb": 1.7 }, "valueMax": null }, "sequence": null, "threadlocker": null, "source": { "title": "OPF-FN509T, ACRO (product page)", "publisher": "Forward Controls Design", "reliability": "secondary", "url": "https://www.forwardcontrolsdesign.com/OPF-FN509T-ACRO_p_517.html", "page": null, "pdfPage": null, "pageUrl": null, "quote": "Torque value for Aimpoint P1/P2 is 26 in lbs, and 20 in lbs for Steiner MPS." } }, { "fastener": "Red-dot optic mounting screws (6-32 flat head, supplied) into EGW rear-dovetail sight mount", "appliesTo": "FN 509 (listed as fitting EGW's Sig #8-cut dovetail mount; EGW lists FN 509 Tactical as NOT fitting) with the EGW 'Trijicon RMR / SRO, Holosun 407c / 507c Mount for Sig Sauer P220, P226, P229, P320' (", "qualifier": "exact", "value": 15, "valueMax": null, "unit": "in-lb", "converted": { "value": { "N-m": 1.7, "in-lb": 15, "ft-lb": 1.2 }, "valueMax": null }, "sequence": "Remove the rear sight, install the EGW mount in the dovetail, tighten the set screw if applicable, place the optic on the mount, then apply blue Loctite and torque the optic screws.", "threadlocker": "Blue Loctite on the provided mounting screws (EGW instructions)", "source": { "title": "Trijicon RMR / SRO, Holosun 407c / 507c Mount for Sig Sauer P220, P226, P229, P320 (EGW product page, installation instructions section)", "publisher": "Evolution Gun Works (EGW)", "reliability": "secondary", "url": "https://egwguns.com/trijicon-rmr-sro-holosun-407c-507c-mount-for-sig-sauer-p220-p226-p229-p320", "page": null, "pdfPage": null, "pageUrl": null, "quote": "Torque mounting screws to 15in/lbs" } }, { "fastener": "Red-dot optic mounting screws (supplied) into EGW rear-dovetail sight mount (Docter/Venom/Viper/FastFire footprint)", "appliesTo": "FN 509 (listed as fitting EGW's Sig #8-cut dovetail mount; EGW lists FN 509 Tactical as NOT fitting) with the EGW 'SIG Sauer P220 P226 P229 P320 Red Dot Mount | Fits Vortex Venom, Viper & Burris FastF", "qualifier": "exact", "value": 15, "valueMax": null, "unit": "in-lb", "converted": { "value": { "N-m": 1.7, "in-lb": 15, "ft-lb": 1.2 }, "valueMax": null }, "sequence": "Remove the rear sight, install the EGW mount in the dovetail, tighten the set screw if applicable, place the optic on the mount, then apply blue Loctite and torque the optic screws.", "threadlocker": "Blue Loctite on the provided mounting screws (EGW instructions)", "source": { "title": "SIG Sauer P220 P226 P229 P320 Red Dot Mount | Fits Vortex Venom, Viper & Burris FastFire | EGW (EGW product page, installation instructions section)", "publisher": "Evolution Gun Works (EGW)", "reliability": "secondary", "url": "https://egwguns.com/vortex-viper-venom-sig-sauer-p220-p226-p229-p320-sight-mount-fits-burris-fastfire-and-docter", "page": null, "pdfPage": null, "pageUrl": null, "quote": "Torque mounting screws to 15 in/lbs" } } ], "notes": "The manufacturer's documents give no torque value. They say: \"Start both mounting screws and tighten them down clock-wise with finger pressure with the provided T10 Torx wrench.\" (FN 509 Owner's Manual (66-100498 R2, 2603), PDF p. 25 (section 11, optic installation step 9)) \"Thread the suppressor or muzzle device on to the barrel and tighten it following the manufacturers recommendations.\" (FN 509 Owner's Manual (66-100498 R2, 2603), PDF p. 27)" }, { "id": "function-check", "title": "Function check", "checks": [ "Verify the pistol is unloaded with no magazine inserted before each check.", "Rack the slide and press the trigger. The striker should release cleanly.", "Hold the trigger to the rear, rack the slide, then release slowly and confirm the reset.", "Press the trigger again to confirm the striker releases.", "Confirm the slide locks open on an empty magazine and the magazine drops free." ], "videos": [] } ], "troubleshooting": [ { "symptom": "The slide will not pull forward off the frame.", "cause": "The striker has not been released, or was inadvertently recocked.", "fix": "With the chamber verified empty and the muzzle in a safe direction, keep the rear of the slide and frame aligned and press the trigger to release the striker, then pull the slide forward." }, { "symptom": "The barrel will not come out of the slide.", "cause": "It is being lifted straight out. The 509 barrel clears the extractor first.", "fix": "Grasp the barrel by its lug, lift it up and around the extractor, then slide it rearward out of the slide." } ], "sources": [ { "n": 1, "id": "fn-509-manual", "title": "FN 509 Owner's Manual", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.wpenginepowered.com/wp-content/uploads/2026/03/2603_FN_509-OM_66-100498_R2.pdf", "accessed": "2026-09-15" }, { "n": 2, "id": "forward-controls-design-32e0e9", "title": "OPF-FN509T, ACRO (product page)", "publisher": "Forward Controls Design", "reliability": "secondary", "url": "https://www.forwardcontrolsdesign.com/OPF-FN509T-ACRO_p_517.html", "accessed": "2026-09-27" }, { "n": 3, "id": "fn-america-llc-dbd219", "title": "Quick Setup & Reference Guide: FN Optics Mounting System (2603)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/wp-content/uploads/2026/03/2603_Quick_Setup_Reference_Guide_FN_OPTICS_MOUNTING_final.pdf", "accessed": "2026-09-27" }, { "n": 4, "id": "fn-america-llc-8e40fd", "title": "FN 509 Owner's Manual (66-100498 R2, 2603)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/wp-content/uploads/2026/03/2603_FN_509-OM_66-100498_R2.pdf", "accessed": "2026-09-27" }, { "n": 5, "id": "fnamerica-specs-bac800", "title": "FN 509® — product page (Specs / Primary Features)", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/products/pistols/fn-509/", "accessed": "2026-10-03" }, { "n": 6, "id": "evolution-gun-works-egw-8862de", "title": "Trijicon RMR / SRO, Holosun 407c / 507c Mount for Sig Sauer P220, P226, P229, P320 (EGW product page, installation instructions section)", "publisher": "Evolution Gun Works (EGW)", "reliability": "secondary", "url": "https://egwguns.com/trijicon-rmr-sro-holosun-407c-507c-mount-for-sig-sauer-p220-p226-p229-p320", "accessed": "2026-10-11" }, { "n": 7, "id": "evolution-gun-works-egw-7ce4c3", "title": "SIG Sauer P220 P226 P229 P320 Red Dot Mount | Fits Vortex Venom, Viper & Burris FastFire | EGW (EGW product page, installation instructions section)", "publisher": "Evolution Gun Works (EGW)", "reliability": "secondary", "url": "https://egwguns.com/vortex-viper-venom-sig-sauer-p220-p226-p229-p320-sight-mount-fits-burris-fastfire-and-docter", "accessed": "2026-10-11" }, { "n": 8, "id": "pat-fn-america-llc-292c17", "title": "FN Patents | FN® Firearms", "publisher": "FN America, LLC", "reliability": "primary", "url": "https://fnamerica.com/fn-patents/", "accessed": "2026-10-13" } ] }