New Products: SIG Sauer MCX Spear LT Upper Receivers

Brownells product acquisition guru Paul Levy shows us the new line of SIG Sauer MCX Spear LT complete upper receiver assemblies. If you have a spare standard "mil-spec" AR-15 lower receiver sitting around (and who doesn’t?), you can mate it to one of these uppers and get a complete Spear LT at a lower "cost of entry" than buying a complete gun off the rack. You can get your upper chambered in 5.56 NATO, .300 Blackout, or 7.62x39mm (slava, tovarisch!), with a 16" carbine barrel or an 11.5" barrel for a pistol or SBR build. The 7.62x39 upper is also compatible with a standard AR-15 lower and uses C-Products 7.62x39 magazines.

 

The MCX Spear LT's recoil system is housed completely within the upper receiver, so it does not need a traditional buffer system and buffer tube (receiver extension). That means it's begging for a folding stock. SIG Sauer answers the call by including a Picatinny stock adapter for your mil-spec lower receiver. That way you can install an MCX stock or any stock that fits an M1913 Picatinny mount. The adapter even has a socket on the underside for a pushbutton QD sling swivel.

 

These uppers all have SIG Sauer's ultra-reliable short-stroke gas piston operating system, with an adjustable gas block accessible via a cutout in the free-floating M-LOK® handguard. The M1913 Picatinny top rail provides a lot of real estate for mounting an optic, and it runs continuously, with the tiniest seam where the receiver meets the handguard.

 

The muzzle device is a flash hider that also serves as a mount for a quick-detach SLX / SLH Next Gen Suppressor (not included), and it's specifically designed to prevent gas leakage to the rear. No need to upgrade the charging handle because it's already ambidextrous and has oversized grasping "ears" to give you a secure hold. The receiver itself has the traditional forward assist and shell deflector. The cam pin path is steel-reinforced to greatly reduce, if not eliminate, cam pin wear on the inside of the receiver.