Sigarms Sig SG 550 SP, SG 551 SP Instructions Manual

 
 
5. Install the gas valve: 

10. Insert bolt assembly: 

3.15 Function check 
 
The function check described below is to be made after every stripping. \
 
 
1. Unload per Section 3.3; 
 
2. Make sure that bolt handle is engaged in correct position; 
 
3. Functions: 
 
a. Safety lever set to “S”, carry out loading movement, pull the 
trigger: 
 

 
3.16. Procedure in case of malfunction 
 
Whenever a SIG SG 550/551 SP no longer works due to a malfunction, 
proceed as follows: 
 

If the weapon still will not fire: 
 

 
4. Maintenance 
 
4.1 Cleaning 
 
The SIG SG 550/551 SP must be cleaned after each period of shooting. 
The following sequence must be adhered to: 
 
 
 
1. Unload weapon per section 3.3.; 
 
2. Field strip the weapon (see Section 3.13.); 
 
3. Clean the barrel and cartridge chamber from the rear. 
 
4. Clean the other parts of the weapon; 
 
5. Lubricate the barrel and chamber using oil or grease; 
 
6. Smear the other parts of the weapon lightly with gun oil or 
grease; 
 
7. Reassemble the weapon in...

5. Function 
 
5.1. Weapon function 
 
5.1.1. Readiness to fire 
 
At the moment of readiness to fire the bolt is closed and locked. 
 

5.1.2. Discharging the shot 
 
By pressing the trigger [11] the hammer [7] is released. The hammer 
is under pressure from the main spring [12] and strikes the firing pin 
[10] which, in turn, impacts against the cartridge primer of the 
cartridge [P] thus discharging the shot. 
 
 
 
 
 
Discharging the shot 
 
 
 
 
 
 
 
 
 
 
 
 
 
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5.1.3. Unlocking and recoil of bolt 
 
The gas pressure, generated by the burning powder, drives the bullet 
up the barrel [13]. As soon as the projectile passes the gas port [15], \
the propellant gas flows through the adjustable gas valve [14]. The gas 
pressure acts on the gas piston [1] which pushes the bolt carrier to the 
rear. 
 
 
 
 
 
Bolt carrier recoil begins 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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During the rearward motion of the bolt carrier [4] the bolt head [5] is 
rotated by the control cam [3] so that the locking lugs [8] are 
disengaged. The bolt is now unlocked. 
 
 
 
 
 
Unlocking begins 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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