The SIG516 uppers allow operators to upgrade their current AR-15/M16/M4-type rifles from direct gas impingement systems to the SIG SAUER® advanced short-stroke pushrod system. This advanced operating system reduces carbon fouling, excessive heat and unburned powder in the action, ensuring reliability and function that is unmatched. A standard 5.56mm NATO chrome-lined chamber and bore ensure reliable function in any environment. 

All models feature a free-floating, aluminum, M1913 quad rail and 1:7 right-hand twist bore configuration. The 10” uppers feature short heavy barrels.

An adjustable gas valve allows operators to increase the flow of gas when using lower pressure ammunition or when adverse conditions require additional energy. Reduced flow and the off-position enhance the use of suppressors. Barrels feature an A2 flash suppressor and are threaded ½x28 TPI, allowing the SIG516 to adapt to a number of aftermarket accessories and suppressor mounts. 

All upper assemblies are shipped with a recoil buffer and action spring. These components must be installed to ensure proper function of the SIG516 upper assembly on your AR-type lower receiver.

This is the Gen2 model and it also comes with a "FULL AUTO" bolt carrier group which allows it to be used in either full auto or semi-auto mode. It includes the buffer and buffer spring. This upper will work perfectly on a standard AR-15 lower receiver and does not convert your lower to fully auto (it just has the capability of functioning normally if you have a select fire rifle such as an M16, M4, etc).

Note: All NFA rules apply.

Link to parts manufacturer