SIG MCX Virtus
- Category
- Carbine
- Barrel
- 406 mm
- Weight, empty
- 3.60 kg
- Introduced
- 2017
About
What it is, and why it matters
The SIG MCX Virtus is a gas-operated, magazine-fed carbine produced by SIG Sauer and chambered primarily in 5.56x45mm NATO. The second-generation MCX platform, introduced in 2017, it uses a short-stroke gas piston operating system with a two-position adjustable gas valve and a dual recoil-spring assembly in place of a traditional AR-15 buffer tube, which permits a side-folding stock. The fully modular receiver allows quick-change barrels and tool-assisted caliber conversion between 5.56x45mm NATO, .300 AAC Blackout, and 7.62x39mm. The patrol carbine ships with a 16-inch cold-hammer-forged barrel, free-floating M-LOK handguard, and ambidextrous controls.
The MCX was originally developed at the request of a U.S. military customer seeking a lightweight, suppressed carbine in .300 AAC Blackout, and the platform's modular receiver later spawned the MCX Spear that won the U.S. Army's Next Generation Squad Weapon program.
The Virtus generation addressed reliability and accuracy concerns from the original 2015 MCX. Barrel options include 9 in (229 mm), 11.5 in (292 mm), and 16 in (406 mm); this entry documents the 16-inch patrol carbine configuration.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- SIG Sauer
- Category
- Carbine
- Country
- United States
- Status
- In production
- Produced
- 2017
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 406 mm
- Overall length
- 908 mm
- Weight, empty
- 3.60 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Gas operated
- Firing mechanism
- Hammer fired
- Trigger
- Single stage
- Capacity
- 30
- Magazine
- Detachable box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Aluminum
- Barrel
- Steel
- Stock
- Polymer
- Finish
- Stealth gray anodized
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 880 m/s
- Effective range
- 500 m
- Rate of fire
- 850 rpm
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.
Features
What it has
What the record lists as fitted, drawn from the catalogue.
Short stroke gas piston
Adjustable gas system
Folding stock
Free floating handguard
M lok handguard
Quick change barrel
Modular caliber conversion
Ambidextrous controls
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 141 5.56x45mm NATO carbines | 3.60 kg | 2.95 kg | Heavier than about 90% |
| Overall lengthAmong 144 5.56x45mm NATO carbines | 908 mm | 838 mm | Longer than about 90% |
| Barrel lengthAmong 150 5.56x45mm NATO carbines | 406 mm | 406 mm | Longer than about 70% |
| Magazine capacityAmong 150 5.56x45mm NATO carbines | 30 | 30 | Near the median |
Answers
Questions about the SIG MCX Virtus
How much does the SIG MCX Virtus weigh?
The SIG MCX Virtus weighs 3.60 kg (7.94 lb) empty.
What caliber is the SIG MCX Virtus?
The SIG MCX Virtus is chambered in 5.56x45mm NATO.
How many rounds does the SIG MCX Virtus hold?
The SIG MCX Virtus holds 30 rounds, fed from a detachable box magazine.
How long is the SIG MCX Virtus?
The SIG MCX Virtus is 908 mm (35.7 in) long overall, with a 406 mm (16.0 in) barrel.
Who makes the SIG MCX Virtus?
The SIG MCX Virtus is made by SIG Sauer (Germany). It was designed by SIG Sauer.
When was the SIG MCX Virtus introduced?
The SIG MCX Virtus was introduced in 2017.
How does the SIG MCX Virtus operate?
The SIG MCX Virtus uses a gas operated 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 Special Operations Command
- United States
- Various law enforcement agencies
- United States
Provenance
Confidence in this record
82%
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-virtus' \ --header 'X-API-Key: your_key'{ "id": "sig-mcx-virtus", "name": "SIG MCX Virtus", "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": "carbine", "name": "Carbine", "description": "Shortened rifles for close-quarters use" }, "country_of_origin": "US", "year_introduced": 2017, "barrel_length_mm": 406, "weight_empty_g": 3600, "action_type": "gas_operated"}