Operator's Manual

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locks the trigger assembly
and buttstock onto the
receiver. See Figure 100.
Rotate the buttstock up into
position and press the upper
take-down pin left to right
until it locks the buttstock
into position. See Figure 101.
Verify the ends of the both take-down pins and the spring tips
are visible on the right side of the rifle. See Figure 102.
WARNING! WHEN THE LOWER PIN RETENTION IS NOT
POSITIVELY RETAINED IT COULD WORK LOOSE DURING
FIRING. IF IT WORKS COMPLETELY OUT, THE TRIGGER
MODULE CAN SEPARATE FROM RIFLE. SEPARATION OF THE
TRIGGER MODULE WILL CREATE AN UNSAFE CONDITION AND
THE RIFLE MAY FIRE UNEXPECTEDLY.
9. Close Feed Tray Cover
Assemble the rifle as described above. Ensure the safety
selector is in the SAFE position. Firmly close the feed tray
cover. Ensure it is locked closed.
27. FUNCTION CHECK
After disassembly and re-assembly, perform a non-firing function
check to ensure proper re-assembly.
1. Before performing the function check, make sure the slide
hammer is cocked and the safety selector is in the SAFE
position as explained in Sections 10 and 11, the rifle is
cleared as described in Section 17 and the muzzle is pointed
in a safe direction.
2. Place the safety selector in the FIRE position.
3. Operate the charging handle, making sure the moving parts
assembly moves freely. Allow the bolt to close on a empty
chamber.
4. Place the safety selector in the SAFE position. Pull the trigger,
nothing should happen.
5. Place the safety selector in the FIRE position, pull the trigger,
the slide hammer should “fall” forward.
6. Pull the charging handle to the rear and release to re-cock the
slide hammer.
7. Place the safety selector in the SAFE position and properly
store the rifle.
28. OPTIONAL TOOLS AND GAUGES
28.1 Headspace Gauge Use
The optional Headspace Gauge included with some
FN M249S
™
models allows for the operator to
regularly check headspace on the barrels. If you
are unsure of headspace operations, seek
assistance from an FN technician or qualified
gunsmith. Law enforcement and military users
should contact their department or unit armorer.
See Figure 103.
To check headspace on the barrel:
1. Before performing the check, make sure the slide hammer is
cocked and the safety selector is in the SAFE position as
explained in Sections 10 and 11, the rifle is cleared as
described in Section 17 and the muzzle is pointed in a safe
direction.
2. Disassemble the rifle as explained in Section 24. Ensure the
bolt assembly and barrel are clean and free of debris as
explained in Section 25.
3. Insert the bolt into the barrel extension and rotate it clockwise
into the locked position without the Headspace Gauge to get a
feel for the natural force required to lock the bolt. Note the
location of the cam lug when locked closed.
4. Remove the bolt and insert the Headspace Gauge into the
chamber (tapered end first). See Figure 104.
5. Insert the bolt into the barrel extension and with slight
pressure attempt to rotate clockwise and lock the bolt closed.
DO NOT FORCE THE BOLT TO CLOSE ON THE HEADSPACE
GAUGE; damage to the gauge, bolt and barrel extension may
result.
6. The bolt should not easily rotate into the locked position.
• If it does not close completely, the barrel is considered to
have correct headspace.
• If it does close completely on the Headspace Gauge, it is
considered to not have correct headspace. Contact FN
America Product Service for service. Law enforcement and
military users should contact their department or unit
armorer.
7. Reassemble the rifle as explained in Section 26.
FIGURE 101
FIGURE 102
FIGURE 100
FIGURE 103
FIGURE 104