Operator's Manual

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NOTE! WHEN NOT IN USE, THE HEADSPACE GAUGE SHOULD
BE STORED IN A PROTECTIVE CASE THAT PROTECTS IT
FROM CORROSION AND DAMAGE. A DAMAGED GAUGE WILL
GIVE FALSE READINGS.
28.2 Breech Bore Gauge Use
The optional Breech Bore Gauge included with some FN M249S
™
models allows for the operator to regularly check throat erosion on
the barrels. If you are unsure of throat erosion check operations,
seek assistance from an FN technician or qualified gunsmith. Law
enforcement and military users should contact their department or
unit armorer.
Breech Bore Gauge is shipped with a protective wax coating that
must be removed before use.
To check the throat erosion using the Breech Bore Gauge
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. Disassembly the rifle as explained in Section 24. Ensure barrel
is clean and free of debris as explained in Section 25.
3. Carefully insert the breech bore gauge into the chamber until
it is seated. Do not use excessive force. See Figure 105.
4. There are two gauge lines on the gauge. Read the gauge by
looking across the rear of the barrel extension. See Figure 106.
The line farthest from the front of the gauge is the “REJECT”
line.
• If the gauge stops at the end of the barrel extension
between the two lines, the barrel is serviceable.
• If the gauge enters the barrel extension beyond the
“REJECT” line, the barrel should be replaced. Contact your
FN Dealer for a new barrel.
5. If the barrel passes, reassemble the rifle as explained in
Section 26.
NOTE! WHEN NOT IN USE, THE BREECH BORE GAUGE
SHOULD BE STORED IN A PROTECTIVE CASE THAT
PROTECTS IT FROM CORROSION AND DAMAGE. A
DAMAGED GAUGE WILL GIVE FALSE READINGS.
28.3 Tubular Socket Wrench Use
The optional Tubular Socket Wrench included with some FN
M249S
™
models allows for the operator to tighten or remove
the carry handle and pistol grip. If you are unsure of these
operations, seek assistance from an FN technician or qualified
gunsmith. Law enforcement and military users should contact
their department or unit armorer.
CAUTION! DO NOT OPERATE THE FN M249S
™
WITHOUT THE
CARRY HANDLE OR PISTOL GRIP FIRMLY IN PLACE.
To remove the barrel carry handle:
1. Before performing any adjustments, 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. Remove the barrel as explained in Section 19 or 24.
3. Insert a section of steel cleaning rod into the hole on either
end of the wrench to act as a “T” handle.
4. Insert the open end of the wrench into the open end of the
carry handle to engage the 10mm nut. Turn the wrench
counterclockwise to loosen and clockwise to tighten
See Figure 107.
CAUTION! DO NOT OPERATE THE FN M249S
™
WITHOUT THE
CARRY HANDLE OR PISTOL GRIP FIRMLY IN PLACE.
To remove the pistol grip:
1. Before performing any adjustments, 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. Remove the trigger module as explained in Section 24.
3. Insert a section of steel cleaning rod into the hole on either
end of the wrench to act as a “T” handle.
4. Insert the open end of the wrench into the open end of the
FIGURE 105
FIGURE 106
FIGURE 107