SIG Virtus

SIG Sauer takes the successful MCX platform to a whole new level

In a world where some groups of people can have anything they want, its fairly easy to tell what the high quality stuff is from their choices. When it comes to quality carbines for gun fighting, there is no shortage of good choices available to consumers, civilian and military. So when three different Tier 1 special operations units from two different countries choose to carry the same tactical carbine, that sort of says something. The carbine these professionals choose to carry is the Sig MCX. The MCX was designed from the ground up with direct input by those who routinely do bad things to bad people, in order to provide all the qualities someone who fights with a gun for a living may desire. But, as with most items, even the MCX can be improved upon. Now it has been, as Sig Sauer recently introduced the Sig Virtus, which in ancient Rome meant virtue, bravery and excellence. The Virtus takes the original MCX to a whole new level. I had previously seen a prototype during a recent visit to Sig Sauer’s uber-modern production facility in New Hampshire, but was sworn to strict secrecy. As one of the lucky few to get an early copy of the Virtus I am finally ready to share my experience, and it’s a good one.

The sculpted and blended receiver lines give the Virtus a unique “high-end” look and feel, and visual conformation that this is not your standard AR-15. Outside of the dual-paddle bolt catch, controls are fully ambidextrous—just like the standard MCX. Unlike the standard MCX, the Virtus is equipped with SIG’s excellent Matchlite Duo two-stage trigger. The rifle ships with one smoked-translucent Lancer L5 30-round magazine.

For those unfamiliar with the MCX platform, it is important to understand the concept of modular, or able to take on many configurations easily. Yes, your typical AR is modular, to a degree. You can hang a lot of stuff on it, change out the upper or control surfaces pretty easily to create, almost, a new gun. But you can’t change the barrel and related parts without some significant armorer effort, the stock doesn’t fold, and you can’t usually switch between calibers. With the MCX you can do all these things, using basic tools and minimal effort.

The lightweight, skeletal handguard of the Virtus is much like the rectangular-shaped version found on the original MCX, but uses an MLOK attachment system instead of Keymod, with MLOK rail cutouts at 3, 6 and 9 o’clock. Enlarged slots can be found along the sides for adjusting the two-position gas piston, and QD sling-mount points on either side of the rear. The rifle’s free-floating, 16-inch CHF barrel has a heavier contour than the original, and is topped with a three-prong flash hider.

The MCX utilizes a carbine length gas system, unique dual-recoil spring short-stroke piston operating system that works reliably suppressed or unsuppressed with SBR or longer barrels. Available in 5.56mm and 300 BLK, the MCX is configurable in multiple barrel lengths, including 9.0, 11.5, and 16 inches that can be easily changed by anyone via simply removing two torx screws. Along with eight different hand guard lengths, Sig Sauer claims the new MCX Virtus will have over 500 (!) different configurations available, making it the most modular, adaptable platform out there. It is also robust, accurate and easy to handle, just like its predecessor. The new Sig Virtus is very similar to its older brother, with some notable upgrades. First, the skeletal handguard is much like the older one, but utilizes an MLOK system vs. a keymod one. It is unique in that it is shaped in the manner of a rectangle with rounded off corners, with MLOK rail cutouts at 3, 6 and 9 o’clock. A Picatinny rail runs across the top to join with the upper receiver, with enlarged slots along the sides for adjusting the two-position gas piston, and QD points on either side of the rear end. The free-floating, CHF barrel has a heavier contour than the original, and is topped with a three-prong flash hider.

The handguard indexes with grooves in the upper receiver and is retained by the lower receiver takedown pin; it’s quickly and easily removed for cleaning and servicing of the gas block and piston components or for swapping in a different length/caliber barrel. The gas block is adjustable between two positions.

Next, the Virtus now sports a two-stage, Sig Duo trigger, which addresses one of the more significant concerns with its predecessor. The Matchlite Duo is supposed to break crisply at 4.5-6 pounds, but mine averaged an even better 4.25. The upper and lower receivers are forged aluminum, with two integrated QD points on the aft end of the lower. The receivers and handguard are Duracoated in an attractive, durable stealth grey or tan finish. Play between the two receivers was virtually nil. Controls are all in the same places found on an AR, except in this case the safety selector and magazine release are both ambidextrous, as is the charging handle. The bolt catch also has an increased engagement surface for easier handling. The stock is the same version previously fielded as an upgrade to the thin wire stock on the original MCX. The improved model is a five-position, inch wide, wedge shaped affair with two QD points that runs on an I-beam about two-thirds of an inch thick. It can be easily folded to the left of the receiver, taking the OAL from 35.5 to 26.5 inches. While not exactly conventional, it is nevertheless effective, lock up is tight when extended, and makes carrying the rifle folded very easy. The stealth grey, 16-inch patrol version I received came in a hard case. No BUIS are provided, through a 30-round Lancer magazine is.


At the heart of the Virtus operating system is this dual-captured recoil spring/bolt-carrier-group assembly, which can not only be largely thanked for the gun’s reliable operation, but also the ability to do away with the buffer tube and add a side-folding stock.

Range work with the MCX Virtus proved enjoyable if unsurprising. Over the course of three different sessions I put 300+ rounds through the Virtus. It ate everything I fed it, from six different types of common metal and polymer magazines. No stoppages or failures of any kind, and no lube whatsoever. Ejection was positive but not excessive, with spent casings falling to a perfect 3-o’clock about four feet away. All mags fed and fell free easily from the slightly flared mag well. At 7.9 pounds empty, the Virtus is not an ultralight but not heavy either, with balance favoring slightly forward. The Virtus handled nimbly, was quick to shoulder, with the ambidextrous controls simple to manipulate. Recoil was soft and manageable, making it easy to take good follow up shots. I particularly liked the proprietary Sig pistol grip, which is similar to a Magpul K2. The MLOK fore end provided an excellent gripping surface, and just as importantly stayed cool during rapid fire strings. Inside ten or so rounds I had the Virtus it dialed in at 50 yards using an Aimpoint T1 on a Larue mount, and proceeded to merrily bang away from a variety of conventional and unconventional shooting positions. A few friends who shot the Virtus were likewise duly impressed.

The side-folding, five-position-adjustable stock locks solidly into place in the open position and easily folds to the left side to create a more compact package. Folded, right-side controls remain easily accessible, and the rifle still able to be fired fired. An ambidextrous charging handle is standard equipment, with the SIG ROMEO 5 red-dot optic and back-up iron sights shown being available separately.

Later, dedicated accuracy testing proved a tad frustrating. This was for two reasons. First, the rather skinny, minimalist stock riding on its tiny I-beam is not entirely optimal for the cheek weld or support necessary to determine true intrinsic accuracy. If this were my personal Virtus, I would likely invest $150 or so in the adaptor Sig Sauer offers for utilizing a receiver extension tube to take any mil spec AR stock. Second, and more significantly, there was me. I was frankly not at the top of my game the day of final accuracy testing. It had already been a long week, and it was only Tuesday. But, deadline looming, I endeavored to persevere. Topped with my Trijicon 4-16x AccuPower on a Larue SPR 1.5 QD mount and shooting from a bench at 100 yards, the Virtus shot an average of about two inches with most of the six different types of ammo I put through it. Under normal circumstances this would be considered quite acceptable, but I knew it could be better. Often I would have four rounds at about an inch, but throw a flyer to open things up despite the Virtus’ very good two-stage trigger. (Insert deleted expletive here). The best groups, not unexpectedly given the Virtus 1:7 barrel twist, came from Hornady .223 75-gr. TAP FPD at 1.25 inches, with the best four in .75 inches. However, Freedom Munitions 5.56mm 55-gr. remanufactured rounds also took honorable mention at two inches for most groups, with similar MOA best-four patterns despite being the bargain ammo. Go figure.

If you’ve never fired an MCX before you’re in for a pleasant surprise. Recoil is comparatively-mild (and without the auditory “cha-chunk” of an AR’s buffer-tube recoil components) and the muzzle nimble—both making for quick follow-up shots. Throughout the 300-plus rounds of testing with various ammunition, the Virtus gave us no stoppages or failures of any kind, and did it without any lube whatsoever.

Bottom line, I firmly believe that the Virtus is capable of consistent MOA groups or better, especially with a standard AR stock and more skilled driver behind it. Regardless, as is the Virtus is capable of excellent practical accuracy, which combined with its many other redeeming qualities is what really matters. To prove that, I decided to end the day with a modified Navy Qual drill, both in and attempt to feel better about myself, and employ the rifle in the manner in which it was primarily designed—moving and fighting at typical engagement ranges. Result: 140 of 15 rounds (5 standing, 5 kneeling and 5 prone with two bolt-lock reloads) inside eight inches at 50 yards with a time of 26.5 seconds. Score: 9 or expert (barely), even by tier 1 operator standards. Mojo recovered.

Not surprisingly, the 1:7 twist rate of the Virtus’ barrel preferred heavier grain-weight bullets. Wearing a Trijicon 4-16x AccuPower riflescope, the rifle’s best 100-yard, five-shot-group from the bench came with Hornady’s 75-gr. TAP FPD .223 Rem, measuring 1.25-inches. The author is confident that with more time and a better ammo selection, this new rifle is capable of even better performance.

The Sig MCX Virtus was everything I expected it to be, and I expected a lot. It is no surprise the MCX is the choice of top end professional gunfighters, and I anticipate this new version will be part of their kit in the not too distant future, if it’s not already. As for price, some say Sig Sauer is a bit too proud of their firearms. However, its also true you usually get what you pay for. At a cost north of $2200, the Sig MCX Virtus is not the cheapest tactical carbine out there, and it will be out of reach for some, though for many of them (including me) it is probably more of a want than a need. But for those who can afford the best and demand it based on their mission requirements, the Virtus may be the ticket. See it at your firearms retailer, or contact Sig Sauer, Dept. OT; Tel.: (603) 610-3000; Web:

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