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4 Aug 2014 - mkillebrew

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MSAR STG-556 - 5.56x45mm

The STG-556 is a short-stroke gas-operated, rotating locking bolt firearm in 5.56x45mm in a bullpup configuration. The gas piston is entirely encapsulated inside the adjustable gas block and upon firing strikes the long operating rod attached to the bolt carrier, forcing the lug atached to the bolt to follow its track in the carrier, rotating and unlocking it from the receiver, which then recoil to cock the hammer again, then under spring force, return to battery. The trigger makes use of two long transfer rods which span the magazine well and enter the polymer hammer back, pushing the sear towards the rear and releasing the hammer. Both the barrel and the bolt lock into the receiver at its rear. Removal of the barrel is accomplished by pushing the takedown knob down and in, then rotating the barrel group, disengaging the lugs from the receiver. The Receiver is then removed by pushing the cross pin in, allowing the assembly to slide forward and out, followed by the bolt carrier assembly. The buttpad is then removed by pressing the button on the top of it while pulling out the takedown pin with its captive swing swivel. After depressing the bolt release, the hammer pack slides out the rear of the stock.

Right Side:

Left Side:


Gas Block, Note Adjustment at End:

Receiver and Gas Block Assembly:


Gas Regulator:

Gas Piston, Regulator, and Spring:

Ejection Port:

Ejection Port - Open Showing Bolt:

Rear of Stock - Left Side:

Magazine - Locked:

Magazine Release:

Magazine Well - Bolt Locked Open:

Magazine Well - Bolt Closed:

Receiver and Gas Block Assembly - Left Side:

Rear of Receiver - Left Side:

Rear of Receiver - Left Side - Charging Handle Locked Back:

Barrel Takedown Lever:

Barrel Assembly Unlocked:

Barrel Assembly:

Barrel Locking Lugs:

Receiver Face:

Receiver Face, Continued:

Rifle - Barrel Assembly Removed:

Receiver Pin - Unlocked:

Receiver and Bolt Group:


Receiver - Trunion:

Bolt Carrier and Bolt - Top:

Bolt Carrier and Bolt, Continued:

Rear of Bolt Carrier, Firing Pin:

Bolt and Bolt Shroud:

Bolt Shroud - Top:

Bolt Shroud - Bottom:


Firing Pin Assembly:

Bolt Carrier and Retaining Plate - Underside:


Stock - Receiver, Bolt Carrier, and Barrel Assemblies Removed:

Sling Swivel on Rear Pin:

Takedown Pin with Sling Swivel:


Rear of Stock - Buttpad Removed:

Hammer Pack:

Hammer Pack, Continued:

Bolt Stop on Hammer Pack:

Hammer Pack - Hammer Released:

Trigger Transfer Bars:

Trigger Transfer Bars spanning Magazine Well:

Trigger Transfer Bars inside Stock at Sear Contact Ends: