Sig Sauer MCX Spear-LT IR Pistol .300 AAC Blackout 9″ 30rd
Video review
Expert review
About this product
The Sig Sauer MCX Spear-LT IR Pistol .300 AAC Blackout 9″ 30rd is a Title I firearm configured as an AR-style pistol, built specifically for short-barrel use and suppressor optimization. It leverages Sig's proven MCX platform with a piston-driven, closed system and a folding pistol brace for transport. This configuration is a direct evolution of military designs, tailored for civilian shooters who understand the ballistic and regulatory advantages of the 9-inch .300 Blackout cartridge.
What is the Sig Sauer MCX Spear-LT used for?
This pistol is optimized for compact, suppressed applications, particularly where terminal ballistics from a short barrel are paramount. The 9-inch barrel paired with the 1:5 twist rate is engineered specifically for stabilizing the heaviest .300 BLK subsonic projectiles, like the 220gr Sierra MatchKing, for whisper-quiet operation with a compatible suppressor. It's a logical choice for defensive use, close-quarters training, or as a highly portable truck/ranch gun, outperforming a standard 5.56mm AR-15 pistol in terms of suppressed energy delivery from less than 10 inches of barrel.
How does the MCX Spear-LT compare to the Stevens 334 .308 Win?
The Spear-LT is engineered for a completely different ballistic and operational envelope than a traditional bolt-action like the Stevens 334 Rifle in .308 Win. Where the Spear-LT prioritizes rapid, semi-automatic fire, modularity, and short-barrel ballistic optimization with a suppressor, the Stevens 334 is fundamentally a precision tool for deliberate, single shots at greater distances. The .308 Winchester from a 20-inch barrel will have vastly superior long-range ballistic coefficient and energy retention past 200 yards, making the Stevens 334 the clear choice for hunting or target shooting at extended ranges. The Spear-LT's domain is within 150 yards with an emphasis on maneuverability and accessory integration.
What does it weigh and what are the dimensions?
Unloaded and without an optic, this pistol weighs approximately 6.2 pounds (2.81 kg), with the majority of mass centered in the monolithic upper receiver. The overall length with the brace deployed is roughly 27.5 inches (699 mm); folding the SB Tactical brace reduces the stored length to about 19.75 inches (502 mm), making it highly packable. The handguard provides 12 inches (305 mm) of continuous M-LOK real estate at the 3, 6, and 9 o'clock positions for mounting lights, lasers, and vertical grips, provided you comply with ATF regulations on overall length and the definition of a 'handgun'.
Who is this NOT for?
This is not a first firearm or a budget-range plinker. The $2,542.99 price point and specialized .300 Blackout cartridge make it an expensive system to acquire and feed, with quality ammunition routinely costing over $1.00 per round. If your primary goal is punching paper at 100 yards for minimal cost, a Stevens 334 in .243 Win is a far more economical and ballistically capable choice. Furthermore, if you are not prepared to navigate the potential regulatory future of pistol braces or the NFA process for a Short-Barreled Rifle (SBR), this configuration carries compliance overhead that a traditional rifle does not.
What's in the box?
Sig Sauer ships this pistol with one 30-round metal magazine, the SB Tactical folding pistol brace already attached, a single-point sling, and the owner's manual. Do not expect a case, optic, suppressor, or any spare parts—this is a professional-grade firearm sold as a complete, ready-to-configure system. The manual includes specific warnings and procedures for the folding brace mechanism and the adjustable gas system, which is critical for tuning when moving between supersonic and subsonic ammunition or adding a suppressor.
Is the MCX Spear-LT worth it at $2542.99?
Yes, but only for the shooter who specifically requires a piston-driven, suppressor-ready .300 Blackout platform of the highest factory pedigree. The price reflects the Gen II NiR Cerakote finish, the proprietary MCX bolt carrier group, and Sig's military-grade manufacturing tolerances. If your use case is general-purpose AR-15 platform familiarity, a direct-impingement AR pistol in 5.56mm from a brand like PSA can be had for under $800, but it will not offer the same sealed-system reliability, optimized twist rate, or out-of-the-box suppressor tuning capability. You are paying a premium for a purpose-built tool, not a generic firearm.
Specs at a glance
Pros & cons
What works
- 1:5 twist rate barrel — optimally stabilizes 220gr+ subsonic .300 BLK for suppressed use
- Folds to 19.75" — reduces storage footprint by over 30% compared to fixed-brace pistols
- Piston-driven system — runs cleaner and cooler than direct impingement, especially suppressed
- Gen II NiR Cerakote — provides 500+ hours of salt spray corrosion resistance per ASTM B117
Trade-offs
- Proprietary lower receiver — locks you into Sig's ecosystem; no using your existing AR-15 lower
- Heavy trigger pull — factory trigger measures 7.5-8 lbs, needs a $150+ aftermarket upgrade for precision work
- High ammunition cost — .300 BLK practice ammo averages $0.85/rd, nearly triple the cost of 5.56mm
Key attributes
| upc | 798681699636 |
| manufacturer | SIG SAUER |
| manufacturer part number | PMCX-300B-9B-IR |
| action | Semi-Auto |
| atf type | Pistol |
| barrel length | 9'' |
| caliber/gauge | .300 AAC Blackout |
| capacity | 30 |
| color | Flat Dark Earth |
| length | 18.8'' |
| magazine included | 1 x 30-Round |
| model | MCX |
| number of magazines | 1 30 rd. |
| package height | 4.3 |
| package width | 11.2 |
| product type | AR |
| safety | Manual |
| shipping weight | 8.2 |
| sights | No Sights / Optics Ready |
| sights type | NONE |
| state restriction (ca) | NO DIRECT SHIP TO CALIFORNIA |
| state restriction (il) | NO SALE TO ILLINOIS PICA |
| state restriction (ri) | NO DIRECT SHIP TO RHODE ISLAND |
| state restriction (wa) | NO DIRECT SHIP TO WASHINGTON |
Frequently asked questions
- Is it compatible with standard AR-15 lowers?
- No, the MCX Spear-LT upper receiver is not compatible with a mil-spec AR-15 lower receiver due to its unique recoil system and lack of a buffer tube tower. It must be paired with a dedicated Sig Sauer MCX lower, which is what this complete pistol includes. The lower uses proprietary takedown pins and a different mag catch geometry.
- Does this work with a standard .223/5.56 suppressor?
- Only if the suppressor is explicitly rated by its manufacturer for .300 AAC Blackout. While the thread pitch is the common 5/8x24, the bore diameter of a .30 caliber suppressor is larger. Firing .300 BLK through a .223-caliber-only suppressor can cause a catastrophic failure. Always verify your suppressor's caliber rating with the manufacturer, such as SureFire or SilencerCo, before mounting.
- Can I replace the 9-inch barrel with a 16-inch barrel?
- Yes, but it requires purchasing a complete MCX barrel assembly from Sig Sauer, which typically costs between $400 and $600. The barrel is not a simple swap like on an AR-15; it is part of a self-contained, quick-change unit that includes the gas piston system. This process takes approximately 2 minutes with the proper tool and does not require re-headspacing.
- How long does shipping to an FFL take?
- Ironclad Armory processes and ships all firearms within 3 business days once your FFL's license is verified. Transit time via FedEx or UPS 2-Day Air is typically 2-3 additional business days. You will receive tracking information once the shipment is tendered to the carrier. The total timeline from order to arrival at your dealer is usually 5-7 business days.
- Does it come with iron sights?
- No, this model ships without iron sights. The flat-top receiver features a full-length Picatinny rail (MIL-STD-1913) for mounting your preferred optic. Sig Sauer offers optional folding backup sights (model # SIG8800026) separately, which are recommended for a duty-grade setup. The rail is 2.75 inches long and provides a solid base for red dots, LPVOs, or night vision devices.