Warning Unloading

Removing cartridges from the magazine does not prevent the rifle from being fired! When there is a cartridge in the chamber and the safety lever is in the "F" (FIRE) position, the cartridge will discharge if the trigger is pulled. It is absolutely essential for the user to know how to completely unload the rifle.

"Completely" means emptying the magazine and removing a chambered cartridge. The safety lever should always be in the "S" (SAFE) position when the rifle is being unloaded.



When the rifle is fired, the same gas pressure which drives the bullet forward also acts through the cartridge case to push the bolt to the rear. That action causes extraction and ejection of the fired case. But, when the bolt is operated by hand, there can be a failure to extract the cartridge from the chamber, or a failure to eject the cartridge clear of the rifle. These failures usually are the result of the bolt not being pulled rearward vigorously, coupled with an accumulation of firing residue in the chamber. From the foregoing it is clear that the gun user must:

1. Always visually check the chamber after opening the bolt to eject a chambered cartridge. If the bolt is not vigorously retracted

when being operated by hand, the extracted cartridge can be "ejected" into the magazine area instead of outside the rifle. (Remember that the magazine should be removed prior to unloading the chamber.)

2. Thoroughly clean the chamber and the extractor as often as necessary to prevent accumulation of grease and dirt.

3. If an empty magazine is in the rifle when the bolt is being hand retracted to extract a cartridge, the cartridge may drop on top of the magazine. Then, when the bolt goes forward, the cartridge will be chambered again! Always remove the magazine before clearing the chamber, and visually ensure that no cartridges remain in the gun.

TO CLEAR A MALFUNCTION ("JAM") 6.0. Procedures In Case Of Malfunction

Should the rifle fail to fire, perform the following actions:

• Continue firing.

If the weapon does not fire after cycling the bolt:

• Insert a fresh magazine;

• Continue firing.

If the weapon still does not fire:

• Put safety lever in the "S" (SAFE) position;

• Remove magazine;

• Ensure the chamber is clear of all ammunition and foreign matter (visual & physical check);

• Turn gas valve on Position 2 when weapon is heavily fouled;

• Insert fresh magazine;

• Place safety lever in the "F" (FIRE) position, continue firing.

If the weapon still will not fire:

• Put safety lever in the "S" (SAFE) position;

• Place safety lever on position "F" (FIRE), and continue firing.

If the rifle malfunction cannot be corrected, the rifle should be returned to SIGARMS, Inc. for evaluation by a factory trained technician.

In the case of a malfunction, the following steps must be followed:

• If the weapon cannot be unloaded immediately and there is any danger of self-ignition due to a hot barrel, wait at least 15 minutes before manipulating the weapon.

• The weapon must remain pointed in a safe direction as long as it is loaded.

WARNING: If your rifle stops firing with a live round in the chamber of a hot barrel (a misfire or jam), remove the round immediately. If you cannot remove the round within 10 seconds, remove the magazine and wait at least 15 minutes with the rifle pointing in a safe direction. This way, neither the user nor any other person would be injured by the possibility of a round "cooking-off" (a round detonating due to the heat of the barrel). Keep your face away from the ejection port while clearing a hot chamber.

WARNING: A cartridge fires when the firing pin impacts the primer, and also can be "discharged" before it is chambered if its primer receives a sharp blow. If a cartridge hangs up, jams, or binds when being chambered or when fed from the magazine into the chamber, do not attempt force it into the chamber by pushing or striking the charging handle. Any jam or feeding problem is a signal to immediately stop using the rifle until the issue can be determined. Most failures of a cartridge to feed or to chamber are caused by a damaged magazine, improper handling, or defective ammunition. Cartridge jams can result in the potentially dangerous situation of a cartridge discharging before it is chambered. If this occurs, the cartridge case will rupture and its fragments will fly out of the rifle with sufficient force to cause injury. Always wear shooting glasses and hearing protectors, and keep your face away from the chamber!


Malfunctions can largely be avoided by cleaning the rifle per section 9.1:

• After each firing session;

• When performance requires switching the gas valve to position 2;

• Whenever a buildup of firing residue is suspected; or

• Whenever the rifle is exposed to extreme environmental conditions (rain, snow, freezing temperatures, etc.).


7.0. Field Strip Disassembly

1. Unload weapon (see section 5.0) — visually and physically check to ensure the rifle is clear of all ammunition;

2. Ensure the bolt is forward;

3. Retract the takedown pin (rear pin) — this pin is captured and does not fully remove;

4. Remove the pivot pin (forward pin): unscrew the pivot pin screw (left side) and remove the pivot pin from the trigger casing;

5. Separate the trigger casing from the receiver;

6. Depress the charging handle catch and remove the charging handle;

556 Rifles Semi AutoGas Rotate Bolt

7. Using the charging handle, push the bolt carrier assembly to the rear and remove it from the receiver;

8. Rotate the bolt head counter clockwise until the lug clears the cam and pull to remove it from the bolt carrier;

9. Pull lower hand guard to the rear and down and remove;

9. Pull lower hand guard to the rear and down and remove;

Sig 556 Trigger Guard

10. Lift upper hand guard at the rear and pull away from gas block;

11. Depress the stop pin and hold. Rotate the gas valve to the left and pull forward to remove;

12. Push the operating rod assembly forward and remove from the gas tube;

13. Depress the stop pin and rotate the gas tube to the left ninety degrees (90°) until the gas tube notch faces the barrel;

12. Push the operating rod assembly forward and remove from the gas tube;

Button Rifle Pull Rod And Head
14. Remove the gas tube from the gas block;

15. Remove the firing pin:

a. Depress the firing pin by pressing the rear of the bolt head against a flat surface until flush and hold;

b. Remove the firing pin stud using an aid (small punch, nail, or pencil) and SLOWLY raise the bolt head until tension is released on the firing pin spring; and c. Remove firing pin and firing pin spring from the bolt head.

c. Remove firing pin and firing pin spring from the bolt head.

Sig 556 Firing Pin

CAUTION: The firing pin is under spring tension when installed in the bolt head. Use caution during removal to prevent injury to yourself and others. The use of eye protection is recommended.

Sig 556 Exploded ViewSig 556 Firing Pin Diagram


7.1. Reassembly

The rifle should always be reassembled in the reverse order of disassembly:

1. Install the firing pin:

a. Insert the firing pin and firing spring spring into the bolt head. The spring should be at the rear. Ensure that the notch on the firing pin is aligned with the firing pin stud.

b. With one hand, place the bolt head (firing pin at the bottom) on a flat surface and depress the firing pin until the notch in the firing pin is aligned with the hole in the bolt shaft for the firing pin stud.

c. With the other hand, insert the firing pin stud and release tension on the firing pin. Ensure the firing pin stud is centered.

2. Install the gas tube:

a. Slide the gas tube (notch down) through the gas block and insert into the gas tube opening in the receiver.

b. Press the gas tube against the gas block (compressing the stop pin) and rotate the gas tube to the right beyond ninety degrees (90°) until the stop pin locks into the gas tube notch.

3. Install the operating rod assembly:

a. Insert the operating rod assembly into the gas tube. Ensure the end with the charging handle notch enters first, notch facing down.

b. Push the operating rod in until fully seated. The operating rod should move freely through the gas tube.

4. Install the gas valve:

a. Ensure the stop pin recesses on the back of the gas valve tab face the barrel.

b. Insert the gas valve into the gas tube (the gas valve will seat over the operating rod).

c. Depress the stop pin and rotate the gas valve to the right to Position 1.

d. Release the stop pin. Check to ensure the gas valve indexes in Positions 1 and 2.

5. Install the upper hand guard:

a. Insert the front into the gas block.

b. Push the rear downward until seated.

6. Install the lower hand guard:

a. Press the hand guard upward against the upper hand guard, ensuring the locking tabs are aligned with each other.

b. Press the lower hand guard forward until the front is secured by the gas block and the pivot pin notch is aligned.

7. Assemble the bolt head and bolt carrier:

a. Place the bolt carrier in your hand, upside down, cam to the front.

b. With the notch facing up, slide the bolt head shaft fully into the bolt carrier.

c. Rotate the bolt head to the left until the notch rests in the cam.

d. Press forward on the firing pin until the bolt head is fully forward.

8. Install the bolt assembly into the receiver:

a. Hold the receiver muzzle down.

b. Holding the bolt carrier, align the left lug on the bolt head with the lug channel in the receiver.

c. Ease the bolt assembly forward until the left and right receiver rails are riding in the rail channels on the bolt carrier.

d. Release the bolt carrier - it should drop freely into the receiver until the bolt is fully locked.

e. Depress the charging handle catch and insert the charging handle into the slot on the bolt carrier.

f. Release the charging handle catch. Tug on the charging handle to ensure it is secured by the charging handle catch.

g. Verify correct installation by pulling the bolt to the rear - it should be connected to the operating rod and move under the tension of the recoil spring.

9. Connect trigger casing assembly to receiver assembly:

a. Mate the receiver and trigger casing together at the front takedown pin, ensuring the pivot pin holes overlap.

b. Install the pivot pin from the right side and secure the pivot pin screw.

c. Rotate the trigger casing until the rear takedown pin holes in the trigger casing assembly and receiver are aligned.

d. Press the rear takedown pin in fully

10. Perform a function check in accordance with Section 7.2. 7.2. Function Check

The function check described below should be performed whenever the rifle is disassembled and reassembled, or whenever proper function of the rifle is suspect.

1. Unload weapon (see section 5.0) - visually and physically check to ensure the rifle is clear of all ammunition;

2. Place the safety lever in the "S" (SAFE) position;

3. Pull the bolt fully to the rear and release;

4. Pull the trigger - the trigger must remain blocked and the hammer must not release;

5. Rotate the safety lever to the "F" (FIRE) position;

6. Pull the trigger and hold - the trigger is not blocked and the hammer releases (falls);

7. With the trigger held to the rear, pull the bolt fully to the rear and release - the hammer must not release;

8. Release the trigger and pull the trigger again - the trigger is not blocked and the hammer must release (fall);

9. Cycle the trigger several times to verify tension and movement of the pressure point spring;

WARNING: Visually and physically verify the magazine is empty before performing the next step.

10. Insert an empty magazine and ensure it is firmly seated;

11. Pull the bolt fully to the rear and release - the bolt must remain locked open;

12. Depress the bolt catch - the bolt must fully close;

13. Pull the trigger; and

14. Place the safety lever in the "S" (SAFE) position.


Inspect the magazine frequently. The magazine follower must move freely and have adequate spring tension so that each cartridge is quickly raised to the feeding position. The magazine lips should be clean and free of cracks, dents, or nicks, so that cartridges are held in their proper feeding position.

When cleaning is necessary, use a solvent that will not rust the metal components or adversely affect the magazine follower. After the magazine has been soaked in solvent to loosen foreign matter, be certain to shake it vigorously (with the loading opening away from you) to remove solvent or residue from within the magazine. Penetrating oils and solvent inside a magazine can "kill" or weaken cartridge primers, which can result in failures to fire or other possibly dangerous malfunctions, such as leaving a bullet in the bore!

After cleaning, always check to be certain that the magazine follower movement and spring tension are correct, and that no solvent or debris remain. Improper reassembly of the magazine spring can cause a potentially dangerous malfunction. If cleaning does not restore proper tension, or if you experience a problem with the magazine, do not use it. Get a new one.



1. Your firearm is delivered factory packaged and preserved with a light coating of protective grease and oils. Before loading make certain that all packing grease and oil has been cleaned from the bore and exposed mechanism.

2. Before you begin to disassemble your firearm for cleaning, always double-check to make sure it is unloaded!

3. After cleaning always check to be sure that no cleaning patch or other obstruction remains in the bore or chamber!

4. For maintenance guidelines, see section 9.0


When transporting your firearm to and from shooting activities, keep it unloaded for your safety and for the safety of others. When storing your firearm, keep it separated from ammunition, under lock and key if possible, and out of the reach of children and other inexperienced or unauthorized persons.

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