Description
The Sig Sauer MCX Spear LT IR Rifle is the lightweight branch of the family Sig built for the militarys Next Generation Squad Weapon program. Where the full SPEAR runs 7.62 and heavy barrels, the LT strips back to 5.56 NATO and 7.5 pounds while keeping the parts that make an MCX an MCX: a short stroke gas piston system, a fully ambidextrous lower and a stock that folds against the receiver because the recoil system lives entirely inside the upper.
Why The Gas Piston And Folding Stock Matter
A short stroke gas piston operating system vents propellant gas against a piston in the handguard rather than routing it back into the receiver. The practical results are a cooler, cleaner action, far better behavior with a suppressor attached, and a rifle that keeps running when a direct impingement gun would be asking for a cleaning. Sig has been building the MCX this way since the platform launched.
Because the recoil spring sits above the barrel instead of in a buffer tube, the stock folds. That is not a feature an AR15 can offer without a proprietary bolt carrier, and it takes a 35 inch rifle down to something that fits a pack or a vehicle trunk. The side folding stock also telescopes for length of pull, and the hinge locks with a push button.
Total weight is 7.5 pounds. The M LOK alloy handguard free floats the barrel and carries lights, lasers and bipods without adding rail weight where none is needed.
Barrel, Finish And Controls
The 16 inch barrel carries a one turn in seven inch twist, which stabilizes everything from light varmint bullets up through heavy 77 grain match loads. The muzzle is threaded half inch by twenty eight and wears Sigs QD flash hider, which doubles as a mount for their suppressor line. MAG5 does not sell suppressors and holds no SOT, so that side of the system has to come from a dealer who does.
The IR in the name refers to Cerakote Gen II NiR in coyote. The coating is engineered to reduce the rifles signature under night vision and thermal observation while still delivering the wear and corrosion resistance any Cerakote finish provides. For most civilian buyers the practical benefit is the finish durability and the color; for anyone working under night vision it is the reason to choose this variant.
Controls are fully ambidextrous, with the safety, magazine release and bolt catch duplicated on both sides. The trigger is Sigs flat blade match trigger rather than a standard mil spec group, and the rifle feeds from standard AR pattern magazines, so the 30 round magazine in the box can be joined by anything already in the safe.
Sig Sauer MCX Spear LT IR Rifle Specifications
- Manufacturer: Sig Sauer
- Model: MCX-SPEAR LT IR, part number RMCX-556N-16B-IR
- Caliber: 5.56 NATO
- Action: Semi automatic, short stroke gas piston
- Barrel Length: 16 inches
- Twist Rate: 1 turn in 7 inches
- Muzzle Threads: 1/2 by 28
- Muzzle Device: Sig suppressor ready QD flash hider
- Overall Length: 35 inches
- Weight: 7.5 pounds
- Stock: Side folding telescoping
- Handguard: Alloy M-LOK, free floating
- Trigger: Flat blade match
- Controls: Fully ambidextrous
- Magazine: 30 round AR pattern
- Finish: Cerakote Gen II NiR coyote
- UPC: 798681699698
One correction worth making, since distributor data occasionally garbles it: this rifle ships with a standard 30 round AR pattern magazine, not a 28 round proprietary unit. Any quality AR15 magazine will run in it. In states that restrict magazine capacity the rifle ships with a compliant magazine or none at all, depending on the destination.
Why Buyers Choose The Sig Sauer MCX Spear LT IR Rifle
Buyers choose the Sig Sauer MCX Spear LT IR Rifle because the folding stock changes what a rifle can do. A 35 inch carbine that folds to roughly 26 inches fits in a pack, a truck console or a discreet bag, and deploys in about a second. No AR15 does that without giving up its buffer system.
The gas piston is the second argument. Suppressor use, sustained fire and cold weather all punish direct impingement guns, and a piston gun shrugs off conditions that would have an AR asking for attention. Sig has more than a decade of MCX production behind this system.
Fully ambidextrous controls, a match trigger, a free floating M-LOK handguard and a suppressor ready muzzle device all come standard. Building an AR to this specification costs more than most people expect, and none of those builds will fold.
Who Should Buy The Sig Sauer MCX Spear LT IR Rifle
This rifle suits someone who wants a defensive carbine that stores compactly, a shooter who plans to run a suppressor and wants a piston gun underneath it, and anyone working with night vision who values the reduced infrared signature of the Gen II NiR coating. It is a premium carbine rather than a budget one, and the feature set reflects that.
Full manufacturer specifications for the Sig Sauer MCX Spear LT IR Rifle are published by Sig Sauer on the official product page. Browse more Sig Sauer rifles and carbines in our rifles category.
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