Description
The MCX platform has earned its reputation the hard way, through military trials, special operations use, and a whole lot of rounds downrange. The MCX-SPEAR LT IR takes that proven short-stroke gas piston system and adds something you won't find on a typical AR: a Gen II NiR Cerakote finish engineered to reduce your infrared signature under thermal and night vision devices. If you run NODs for hog control, predator hunting, or low-light training, that coating matters. And even if you never flip on a thermal, it still delivers serious wear and corrosion resistance in the Coyote FDE color that looks right at home on this rifle.
What Sets the MCX-SPEAR LT IR Apart
The LT chassis trims weight where it counts, bringing this rifle in around 7.5 pounds with a lightened 16" cold hammer forged carbon steel barrel in a 1:7 twist. The muzzle wears a SIG QD flash hider that's suppressor-ready right out of the box, and the barrel threads are the standard 1/2×28 with a tapered shoulder. Up top you get a full-length Picatinny rail with no sights installed, so you're free to mount whatever optic fits your mission. The M-LOK handguard uses added attachment screws for extra rigidity, which keeps lights and lasers from shifting your point of impact when you load up the rail.
Built for Real-World Handling
Sig's Tele-fold stock both telescopes and folds flat against the receiver with a push-button hinge, and thanks to the piston system, the rifle fires with the stock folded. That makes for compact storage in a truck, pack, or discreet case without giving up a proper cheek weld when it's time to shoot. Controls are fully ambidextrous, including the bolt catch and release, and the non-reciprocating side and rear charging handles give you options no matter which shoulder you run. The flat-blade two-stage Matchlite Duo trigger breaks clean, and since the lower accepts AR-15 pattern triggers and magazines, upgrades and mags are easy to come by. It ships with one 30-round polymer magazine and swaps barrels and handguards with the rest of the MCX-LT lineup, so the platform can grow with you.
Key Specifications
- Manufacturer: SIG SAUER
- Model: MCX-SPEAR LT IR
- MPN: RMCX-556N-16B-IR
- UPC: 798681699698
- Caliber: .223 Rem / 5.56 NATO
- Action: Semi-Auto, Short-Stroke Gas Piston
- Barrel: 16" Cold Hammer Forged Carbon Steel
- Twist Rate: 1:7
- Muzzle Threads: 1/2"-28 TPI, Tapered Shoulder
- Muzzle Device: SIG Suppressor-Ready QD Flash Hider
- Capacity: 30+1
- Stock: Telescoping/Folding with Push-Button Hinge
- Trigger: SIG 2-Stage Matchlite Duo, Flat Blade
- Handguard: Alloy, M-LOK/Picatinny
- Finish: Coyote FDE Gen II NiR Cerakote (Reduced IR)
- Weight: 7.5 lbs
What’s Included
- Sig Sauer MCX-SPEAR LT IR 5.56 NATO 16" rifle
- One 30-round polymer magazine
- Cable lock
- Owner's manual
Frequently Asked Questions
What does the IR finish on the MCX-SPEAR LT IR do?
The Gen II NiR Cerakote coating is formulated to reduce the rifle's visibility under night vision and thermal imaging devices. It's a big deal for night hunters and anyone training under NODs. Beyond the low-signature benefit, it also adds strong wear and corrosion resistance, so the finish holds up to rough field use.
Does the MCX-SPEAR LT IR take standard AR-15 magazines and triggers?
Yes on both counts. The lower feeds from standard AR-15 pattern 5.56 magazines and accepts AR-15 compatible trigger groups, so aftermarket upgrades are simple. It ships with one 30-round polymer mag from the factory.
Can you fire this rifle with the stock folded?
You can. Because the MCX uses a short-stroke gas piston system instead of a buffer tube, there's nothing in the stock required for cycling. The Tele-fold stock also telescopes for length of pull adjustment, and the push-button hinge makes folding it quick and secure.
Is the MCX-SPEAR LT IR suppressor ready?
It is. The 16" barrel comes threaded 1/2×28 with a tapered shoulder and wears a SIG QD flash hider that works as a quick-detach mount for compatible SIG suppressors. If you run a different can, the standard thread pitch accepts most 5.56 direct-thread and mount-style muzzle devices.





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