SIG MCX Spear
- Category
- Assault Rifle
- Barrel
- 330 mm
- Weight, empty
- 3.80 kg
- Introduced
- 2022
About
What it is, and why it matters
The SIG MCX Spear is a select-fire assault rifle chambered in 6.8x51mm (.277 SIG Fury), produced by SIG Sauer Inc. since 2022. This American-manufactured firearm reflects the engineering traditions and quality standards of its country of origin, designed to meet the demands of both civilian and professional users in a competitive global marketplace. Featuring a 20-round magazine capacity, this assault rifle offers generous firepower for duty use and home defense. The 13.0-inch barrel maximizes accuracy potential and ballistic performance, making this an excellent choice for target shooting, competition, or field use. At 3800g (134.0 oz), this is a substantial firearm whose weight contributes to reduced felt recoil and enhanced stability during precision shooting. The aluminum alloy frame achieves a notable weight reduction compared to all-steel construction while maintaining the structural rigidity required for safe, reliable operation. This firearm represents its manufacturer's commitment to delivering a well-engineered, reliable product that serves the needs of discerning shooters seeking quality, accuracy, and dependable performance from a proven platform.
The SIG MCX Spear represents the most significant change in US infantry small arms since the adoption of the M16 in the 1960s. The NGSW program was born from the realization that 5.56mm NATO could not reliably defeat modern body armor worn by near-peer adversaries. The revolutionary hybrid-case ammunition operates at chamber pressures 33% higher than conventional cartridges, delivering rifle performance previously only achievable with much larger weapons.
The NGSW program was driven by the need to defeat near-peer adversary body armor at extended ranges, which 5.56mm NATO could not reliably accomplish. The 6.8x51mm cartridge uses a revolutionary hybrid case with a steel base and brass body, allowing safe operation at 80,000 PSI chamber pressure - far exceeding conventional cartridges. The civilian MCX Spear is semi-automatic only. In September 2025, SIG Sauer presented an improved M7 with a shortened 10.5-inch barrel and lightened internals. The rifle is designed to be used with the XM157 Fire Control optic, an integrated next-generation squad weapon fire control system with ballistic computer.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- SIG Sauer
- Category
- Assault Rifle
- Country
- United States
- Status
- In production
- Produced
- 2022
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 330 mm
- Overall length
- 973 mm
- Weight, empty
- 3.80 kg
- Weight, loaded
- 4.46 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Gas operated short stroke
- Firing mechanism
- Hammer fired
- Trigger
- Two stage
- Capacity
- 20
- Magazine
- Detachable box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Aluminum alloy
- Barrel
- Steel
- Stock
- Polymer
- Finish
- Cerakote
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 838 m/s
- Muzzle energy
- 2570 J
- Effective range
- 600 m
Trajectory
What the round does downrange
Solved from the muzzle figures and the bullet. The dashed rule is the effective range on the record, and the crosses are the steps the solver returned.
No load solved for this record yetThe flight path is computed from a cartridge and a bullet. This record has no ammunition filed against its chambering, so there is nothing to solve.
Features
What it has
What the record lists as fitted, drawn from the catalogue.
Folding stock
Adjustable stock
Select fire
Suppressor ready
Free floating barrel
M lok handguard
Ambidextrous controls
Quick change barrel
Multi caliber
Picatinny rail
Rotating bolt
Short stroke gas piston
Standing
How it compares
Each figure against the firearms of the same type and cartridge that record it, or of the same type where that cartridge has too few. Positions are read to the nearest tenth.
| Measurement | This firearm | Median | Position |
|---|---|---|---|
| Empty weightAmong 274 assault rifles | 3.80 kg | 3.58 kg | Heavier than about 70% |
| Overall lengthAmong 271 assault rifles | 973 mm | 915 mm | Longer than about 80% |
| Barrel lengthAmong 271 assault rifles | 330 mm | 415 mm | Shorter than about 90% |
| Magazine capacityAmong 276 assault rifles | 20 | 30 | Among the smallest capacities |
Answers
Questions about the SIG MCX Spear
How much does the SIG MCX Spear weigh?
The SIG MCX Spear weighs 3.80 kg (8.38 lb) empty and 4.46 kg (9.83 lb) loaded.
What caliber is the SIG MCX Spear?
The SIG MCX Spear is chambered in 6.8x51mm Common Cartridge.
How many rounds does the SIG MCX Spear hold?
The SIG MCX Spear holds 20 rounds, fed from a detachable box magazine.
How long is the SIG MCX Spear?
The SIG MCX Spear is 973 mm (38.3 in) long overall, with a 330 mm (13.0 in) barrel.
Who makes the SIG MCX Spear?
The SIG MCX Spear is made by SIG Sauer (Germany). It was designed by SIG Sauer Engineering Team.
When was the SIG MCX Spear introduced?
The SIG MCX Spear was introduced in 2022.
How does the SIG MCX Spear operate?
The SIG MCX Spear uses a gas operated short stroke action, and its firing mechanism is hammer fired.
Compatibility
Which parts fit this firearm
Studio
Every part that mounts on this, resolved
Not a list the maker typed out: the answer comes from the mounts this firearm exposes and the interface each part needs, so it stays right when either one changes.
- Every part that mounts on any firearm in the catalogue
- Interface standards, platforms and fit overrides
- The same answers through the API and the MCP server
Requires a signed-in GunSpec account on the Studio plan. The answer is computed per part, so it is not part of the public record.
Provenance
What the record holds
Every figure above was taken from one of these pages. The confidence reflects how much of the record came from a page a claim can be checked against.
In service
- United States Army
- 2022
- 75th Ranger Regiment
- 2023
- 101st Airborne Division
- 2024
Provenance
Confidence in this record
78%
Stockists
Where to buy
Offers link straight to the shop. GunSpec never takes the order.
No shop has listed this firearm yet
Stock and prices come from the shops themselves. If you sell this firearm, you can list it and it appears here.
List a firearmMCP
Ask an assistant about it
The same record, reached the way a person asks for it rather than the way a program does.
Ask GunSpec
Works with
Point an MCP client at GunSpec and it answers from the catalogue rather than from memory. A free key covers the read tools.
API
The call that returns this record
The same fields, in the same units, from the same endpoint the page reads.
curl --request GET \ --url 'https://api.gunspec.io/v1/firearms/sig-mcx-spear' \ --header 'X-API-Key: your_key'{ "id": "sig-mcx-spear", "name": "SIG MCX Spear", "manufacturer": { "id": "sig-sauer", "name": "SIG Sauer", "countryCode": "DE", "foundedYear": 1985, "website": "https://www.sigsauer.com", "logoUrl": null, "description": null, "status": null, "defunctYear": null, "stateOwned": null, "makesFirearms": null, "parentId": null, "predecessorId": null, "createdAt": "2026-02-11 23:44:40", "updatedAt": "2026-02-18 03:40:48", "version": "944f4088befdcee3b0aa7caf122998351ef3d78abc525a2bdec9df81e65a6b30" }, "category": { "id": "assault-rifle", "name": "Assault Rifle", "description": "Selective-fire rifles chambered in intermediate cartridges" }, "country_of_origin": "US", "year_introduced": 2022, "barrel_length_mm": 330, "weight_empty_g": 3800, "action_type": "gas_operated_short_stroke"}