GENERAL SAFETY INFORMATION AND MECHANICAL CHARACTERISTICS
The safety warnings in this manual are important. By understanding the dangers inherent in the use of any firearm, and by taking the precautions described herein, you can enjoy complete safety in the use of your rifle. Failure to heed any of these warnings may result in serious injury to you or others, as well as severe damage to the firearm or other property. SIGARMS, Inc. shall not be responsible in any manner whatsoever for malfunctioning of the firearm, physical injury or property damage resulting in whole or in part from:
1) criminal or negligent discharge;
2) improper or careless handling;
3) unauthorized modifications;
4) defective, improper, hand-loaded, or reloaded ammunition;
6) neglect; or
7) other influences beyond our direct and immediate control.
This limitation applies regardless of whether liability is asserted on the basis of contract, negligence, or strict liability (including any failure to warn). Under no circumstance shall SIGARMS, Inc. be liable for incidental or consequential damages, such as loss of use of property, commercial loss, and loss of earnings or profits.
Always wear safety glasses and ear plugs or "earmuff" type protectors whenever you are shooting. Always make certain that persons close to you are similarly protected. Unprotected eyes may be injured by powder, gas, carbon residue, lubricant, metallic particles, or similar debris which may emanate occasionally from any firearm in normal use. Without ear protection, repeated exposure to shooting noise may lead to cumulative, permanent hearing loss.
2.0. Mechanical Characteristics And Weapon Theory
2.1. Weapon Description
The SIG 556 Rifle is a semi-automatic, gas operated weapon, with a rotary bolt mechanism. Semi-automatic means one round will fire each time the trigger is pulled until the magazine is emptied of ammunition. The rifle is chambered in 5.56mm NATO and is compatible with .223 Remington ammunition.
The barrel is mechanically mated to the receiver. The flash suppressor is screwed onto the muzzle end of the barrel which features a ^ x 28 TPI thread pattern. The gas block, which is fixed on the barrel, contains the gas port, locates the gas system (gas tube and operating rod), accepts an optional front sight and also serves as support for the hand guards. The receiver guides the bolt and bolt carrier and houses the locking system. An accessory mounting rail is fixed to the upper part of the receiver, providing an attachment point for sighting systems and other accessories.
Charging handle catch
Charging handle catch
The bolt consists of two main parts:
• Bolt Head a. Bolt Carrier: The bolt carrier guides the bolt head, controls the locking and unlocking by means of the cam, holds the operating rod, and cocks the hammer.
b. Bolt Head: The bolt head locks the bolt assembly, houses the firing pin and extractor and feeds the cartridges from the magazine to the chamber.
2.1.4. Hand Guards
The hand guards protect the barrel and the gas system from damage and provide protection from burning. The integrated accessory mounting rails provide attachment points for various devices, such as lights, lasers, sights, and bipods.
Upper hand guard Short accessory rail (left & right sides)
Upper hand guard Short accessory rail (left & right sides)
2.1.5. Trigger Casing Assembly And Butt Stock
The trigger casing assembly contains the internal components of the firing and safety mechanisms, bolt catch, magazine well, magazine release, and butt stock assembly.
The safety lever, located on both sides of the trigger casing, can be set to two positions:
• Position "S:" The weapon is locked in the safe position.
• Position "F:" The weapon will fire in the semi-automatic mode.
The trigger guard may be released from its normal position to make the trigger accessible for shooting with gloves. For safety reasons the trigger guard must not be released until just before firing the weapon, and after firing should be immediately returned to the normal (closed) position.
CAUTION: Be careful of accidental discharges when inserting gloved fingers into the trigger guard.
The SIG 556 rifle is equipped with a collapsible stock, featuring integral sling attachment points and battery storage compartment.
2.1.6. Gas Valve Position
The gas volume required for the function of the SIG 556 rifle can be controlled by the gas valve. The gas valve has two positions:
a. Position 1 (Rib of gas valve in vertical position).
b. Position 2 (Rib of gas valve in the slanted position).
When cycling or ejection problems are encountered due to heavy fouling, the gas valve can be moved to Position 2 by rotating clockwise as far as the stop. In this position, a larger gas volume is released against the operating rod. The need to utilize the gas valve in Position 2 is an indication that the rifle requires cleaning.
CAUTION: In the case of a hot or heavily fouled weapon, use a cartridge or auxiliary aid to prevent burns to your fingers.
CAUTION: Firing with the gas valve in Position 2 is an exception. As soon as normal function returns, the gas valve must be returned to Position 1. Continued operation with the gas valve in Position 2 will increase recoil and place unnecessary stress on the rifle. The rifle should be cleaned as soon as conditions permit.
WARNING: Always ensure the weapon is unloaded and clear of ammunition when manipulating the gas valve.
2.1.7. Butt Stock Operation
1. The butt stock provides for easy adjustment of length to accommodate the individual shooter or for storage.
2. To adjust the length of the butt stock, depress the adjusting latch and move the stock to the desired position. Ensure the stock is fully locked in position before firing!
3. To remove the butt stock, pull down on the adjusting latch and remove the stock from the receiver extension.
3. The butt stock features a battery storage compartment, which is accessed by peeling the butt pad off the stock at the 12 o'clock position. The pad is attached to the stock by a rivet at 6 o'clock.
4. The butt stock features two (2) sling attachment points. 2.1.8. Trigger Guard Operation
1. The trigger guard opens to accommodate firing the rifle with gloves or mittens.
2. To open the trigger guard, depress the spring loaded pin on the front right and rotate downward.
The SIG 556 rifle features integrated accessory mounting rails on the upper receiver and hand guards. These rails may be used for attaching a variety of sighting systems, both optical and fixed. The accessory rails are compatible with all Picatinny standard mounting systems. Optional fixed ("iron") sights are available as an accessory from SIGARMS.
The rifle ships standard with (1) 30-round magazine. The SIG 556 is compatible with M16/AR-15 type magazines.
2.2. Technical Specifications
Caliber Total length
Length with stock collapsed Barrel length Number of grooves Rifling
Weight (w/out mag)
5.56mm NATO (.223 Remington) 37 inches 33.5 inches 16 inches 6
Specifications are approximate and subject to change without notice.
A full range of accessories for the SIG 556 are available from SIGARMS or through your local dealer.
The SIG 556 has a manual safety which is located on the left and right side of the trigger casing, just forward of the pistol grip and above the trigger. The safety levers may be operated from either side.
The safety is "on" when the safety lever is in the "S" (SAFE) position and the trigger guard is closed. In this position, the rifle cannot be fired with a normal pull of the trigger.
The safety lever should always be in the "S" (SAFE) position except when the shooter is actually firing the rifle. The safety lever should be moved to the "S" (SAFE) position whenever the shooter ceases firing, even temporarily.
The safety is "off" when the safety lever is in the "F" (FIRE) position. Thus when the safety lever is in the "F" (FIRE) position the rifle will fire in the semi-automatic mode each time the trigger is pulled until all the ammunition is expended.
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