← FN SCAR 17S reference page · This work order as JSON ·
Work order — FN SCAR 17S
Taking the firearm apart for a job such as refinishing, and putting it back together to specification. Generated from the Pew-Takedown entry last updated 2026-10-29. Confidence: medium.
| Work order # | |
|---|---|
| Customer | |
| Model on the bench | |
| Serial number | |
| Finish / colour | |
| Received | |
| Technician |
- FN Herstal limits owner disassembly: Trigger module, buttstock module, moving parts (bolt carrier, charging sled, bolt removed from carrier), gas regulator and piston. Do not disassemble the bolt, the buffer or the charging sled further.
- This work order is written for the FN SCAR 17S. It is reported to cover FN SCAR 16S in 5.56mm; Mk 16 and Mk 17 military variants — if the firearm on the bench is one of those, check the torque notes: values do not always carry over.
Shop difficulty: Tier 2 of 3
The upper is a monolithic receiver; the barrel comes out on six captive Torx screws torqued in sequence, and the trigger module, bolt carrier and stock come off with finger pressure. FN treats the trigger module and other inner assemblies as factory-only, and a barrel removal means a headspace check. There are few parts to handle, but the torque spec, headspace gauging and a sealed trigger module make it moderate. Pew-Takedown's rating, not the manufacturer's.
Bench time: strip ~40 min, rebuild ~60 min (estimate). Actual: strip ______ rebuild ______
Special tools:
- Inch-pound torque wrench with T-25 Torx bit — Barrel screws, 62 in-lb (7 N·m)
- GO/NO-GO headspace gauges (7.62x51) — After the barrel is refitted
- M16/AR15 A2 front sight tool — Front sight post
- Muzzle device wrench — Flash hider
Watch for:
- FN says the inner mechanism assemblies (trigger module internals, bolt) are finely fitted and go back to FN for anything past the field strip. (both; FN America)
- The six barrel screws are captive: they are backed to the end of travel but not removed, then torqued back in a rear-to-front alternating sequence at 62 in-lb; a ft-lb wrench strips them. (both; FN America, LLC)
- Any barrel off/on needs a GO/NO-GO headspace check by an armorer. (reassembly; FN America, LLC)
1. Clear and make safe
- Point the muzzle in a safe direction and keep your finger off the trigger.
- Place the selector on safe.
- Press the magazine release and remove the magazine.
- Pull the charging handle fully to the rear and lock the bolt back if the rifle has a hold-open.
- Inspect the chamber and magazine well with a light, then physically confirm the chamber is empty.
Warning: Look and feel. Both, every time. - Remove all live ammunition from the work area.
2. Disassemble
Field Strip
- Complete the Clear and Make Safe procedure and release the bolt forward.
- Push out the two receiver takedown pins.
- Separate the upper receiver from the lower receiver.
- Withdraw the bolt carrier group and its recoil spring guide rods rearward out of the upper receiver.
Warning: The recoil springs are under compression. - Remove the firing pin retaining pin, withdraw the firing pin, rotate and lift the cam pin, and withdraw the bolt.
- Rotate and withdraw the gas piston and its components from the gas block, noting orientation.
3. Refinish
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.
| Component separated | Out | Coated | Back in |
|---|---|---|---|
| Takedown pins | |||
| Upper receiver assembly | |||
| Bolt carrier group | |||
| Recoil spring assembly | |||
| Firing pin | |||
| Cam pin | |||
| Bolt | |||
| Gas piston |
| Component | Material | Factory finish | Source |
|---|---|---|---|
| Receiver (upper) FN SCAR 17S NRCH, 16.25in (page lists BLK, FDE and GRY colour SKUs) | aluminum | Hard-anodized | [8] |
| Barrel FN SCAR 17S NRCH, 16.25in (page lists BLK, FDE and GRY colour SKUs) | — | chrome-lined | [8] |
| Stock FN SCAR 17S NRCH, 16.25in (page lists BLK, FDE and GRY colour SKUs) | polymer | — | [8] |
| Magazine FN SCAR 17S NRCH, 16.25in (page lists BLK, FDE and GRY colour SKUs) | Steel | — | [8] |
4. Reassemble
Reassembly
- Reinstall the gas piston and its components in the correct orientation.
- Fit the bolt into the carrier, install and rotate the cam pin, then the firing pin and retaining pin.
- Insert the bolt carrier group and guide rods into the upper receiver and seat them.
- Mate the upper to the lower and press both takedown pins fully home.
- Cycle the action several times and perform the function check.
5. Torque
| Fastener | Specification | Sequence | Source | Applied | Init. |
|---|---|---|---|---|---|
| Barrel screws: four rear barrel extension screws and two forward barrel support screws (captive, TORX T-25) FN SCAR 16S and 17S |
62 in-lb 7 N·m · 5.2 ft-lb |
Seat the barrel extension lugs in the receiver cutaway, slide rearward until all barrel extension screws align, guide the front barrel support into the receiver; tighten the barrel screws starting at the rear of the barrel extension (alternating sides) and moving forward, per the 1-6 sequence in Figure 11, applying downward pressure. | [4] PDF p. 2 (Barrel Assembly Installation, (PDF p. 2) | ||
| Barrel extension screws (TORX T-25), refitting the barrel after NRCH conversion FN SCAR 16S/17S (NRCH kit P/N 20-100505 for 17S/20S) |
62 in-lb 7 N·m · 5.2 ft-lb |
Starting from the rear, in the order of Figure 18 (1-6), applying downward pressure and turning clockwise. | [5] PDF p. 12 (PDF p. 12) | ||
| NRCH front plate screws (2.5 mm hex) FN SCAR 16S/17S converted with FN's NRCH kit (P/N 20-100505 for 17S/20S) |
22.1 in-lb 2.5 N·m · 1.8 ft-lb |
Threadlocker: Loctite 263 permanent high strength thread locker (or equivalent); allow 24 hours cure |
[5] PDF p. 10 (PDF p. 10) | ||
| SCAR-SC receiver rear plate screws (four 2.5 mm side screws, one 3 mm top screw) FN SCAR 16S/17S/20S fitted with FN's SCAR-SC rear stock ("installation procedures for SCAR 16S, SCAR 17S and SCAR 20S are identical") |
22.1 in-lb 2.5 N·m · 1.8 ft-lb |
Threadlocker: Loctite 263 permanent high strength thread locker (or equivalent); allow 24 hours cure |
[6] PDF p. 2 (PDF p. 2) | ||
| M-LOK QD sling mount screws (5/32" hex) FN SCAR 16S, 17S, 20S |
max. 35 in-lb 4 N·m · 2.9 ft-lb |
[7] PDF p. 57 (M-LOK QD sling mount) (PDF p. 57) | |||
| M-LOK vertical foregrip screws (5/32" hex) FN SCAR 16S and 17S |
max. 15 in-lb 1.7 N·m · 1.2 ft-lb |
[7] PDF p. 58 (22.4 Vertical foregrip) (PDF p. 58) |
Reported by other sources — not the manufacturer
| Fastener | Reported value | Sequence | Source | Applied | Init. |
|---|---|---|---|---|---|
| Rear barrel extension screws (4, T-25 Torx) FN SCAR 16 and 17 (instructions for fitting the Midwest Industries MI-S1617 extension rail, which reuses the factory screws) Reported by Midwest Industries, Inc. (secondary) — not the manufacturer |
62 in-lb 7 N·m · 5.2 ft-lb |
Start the forward barrel screws (do not tighten), slide the barrel rearward and start the 4 rear barrel extension screws (do not tighten), fit the rail, then tighten the four rear barrel extension screws in an alternating pattern; then the six remaining T-25 screws in the rail and front trunnion to 45 in/lbs. 'DO NOT attempt to remove the receiver assembly screws, located in the middle of each block.' | [2] PDF p. 1 (PDF p. 1) | ||
| Barrel screws (factory four T25 screws) FN SCAR (barrel assembly to upper receiver; KDG MREX MkII rail instructions) Reported by Kinetic Development Group (KDG) (secondary) — not the manufacturer |
62 in-lb 7 N·m · 5.2 ft-lb |
Slide the barrel (with rail) assembly into the upper receiver and tighten the factory four T25 screws in a crisscross pattern. | [3] | ||
| Rail and front trunnion screws (6, T-25), with MI extension rail fitted FN SCAR 16/17 fitted with Midwest Industries MI-S1617 extension rail Reported by Midwest Industries, Inc. (secondary) — not the manufacturer |
45 in-lb 5.1 N·m · 3.7 ft-lb |
[2] PDF p. 1 (PDF p. 1) |
Notes: The manufacturer's documents give no torque value. They say: "Reinsert the safety selector lever screw into the larger hole of the safety selector lever and hand-tighten with a 5/64” flathead screwdriver until the screw is flush with the safety selector lever body (Figure 69). Do not over tighten." (FN SCAR 16S/17S/20S Owner's Manual (2512), PDF p. 55) "Install the rear sight assembly to the receiver top rail using a T25 wrench. Use only enough torque to snug the clamping screw." (Instructions for FN SCAR-SC Rear Stock (2407), PDF p. 2)
Fit or check on rebuild
- Barrel screw torque and sequence — Rear-to-front, alternating, 62 in-lb
- Headspace — Bolt/barrel combination must be gauged after a barrel change
- Zero — The barrel moves relative to the top rail and optics; re-zero
6. Function check
- Verify the rifle is unloaded with no magazine inserted before each step.
- Cycle the action by hand and confirm the bolt locks and returns fully to battery.
- With the selector on safe, press the trigger. The hammer must not fall.
- Move the selector to fire, cycle the action, and press the trigger. The hammer should fall.
- Hold the trigger back, cycle the action, and release slowly to feel the disconnector reset.
- Confirm the magazine seats and locks positively and any hold-open engages on an empty magazine.
- Confirm the folding stock locks positively in the extended position.
- Confirm the gas regulator is on the correct setting.
If any check fails, the firearm is not safe to fire. Stop and see a licensed gunsmith.
Sources
- FN SCAR 17S Operator’s Manual — FN America primary
- MI-S1617 FNH SCAR 16, 17 Extension Rail Installation Instructions — Midwest Industries, Inc. secondary
https://midwestindustriesinc.com/content/installation-instructions/SCAR-Extension-Rail-MI-S1617-Instructions.pdf - MREX MkII Installation Instructions — Kinetic Development Group (KDG) secondary
https://kineticdg.com/instruction/mrex-mkii-installation-instructions/ - Instructions for FN SCAR 16S and 17S Barrel Change (63903, 2303) — FN America, LLC primary
https://fnamerica.com/wp-content/uploads/2024/08/SCAR-Carbine-Accessory-Barrel-Instructions_63903_2303-1.pdf - Instructions for FN SCAR Non-Reciprocating Charging Handle Kit (FN002 R3) — FN America, LLC primary
https://fnamerica.com/wp-content/uploads/2024/02/FN002-SCAR-NRCH-Instruction-Manual-R3-05-20-2269.pdf - Instructions for FN SCAR-SC Rear Stock (2407) — FN America, LLC primary
https://fnamerica.com/wp-content/uploads/2025/02/2407_FNSCAR-SC-Stock-Install.pdf - FN SCAR 16S/17S/20S Owner's Manual (2512) — FN America, LLC primary
https://fnamerica.com/wp-content/uploads/2026/01/2512_FNSCAR_16S17S20S_OM_.pdf - FN SCAR® 17S NRCH — product page (Specs / Primary Features) — FN America, LLC primary
https://fnamerica.com/products/rifles/fn-scar-17s-nrch/ - Autoloading Rifle Owner's Manual FN SCAR 16S and 17S (2016) — FN America primary
https://s3.amazonaws.com/files.ammunitiondepot.com/fn-firearms/carbines-discontinued/fn-scar-16s-17s-owners-manual-2016.pdf
| Reassembled and function-checked by | Date |
|---|
Educational guide only. Some information comes from non-authoritative sources. Always consult your manufacturer's manual and a licensed gunsmith. Verify your firearm is unloaded before every procedure. Full disclaimer: https://github.com/Fundamental-build-LLC/Pew-Takedown
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.