Sig Sauer MCX
Tactical Air Rifles and Optics Part 1
By Dennis Adler
This model of the Sig Sauer MCX tactical air rifle is based on the military version with noise suppressor and solid shoulder stock (which is used to house the 88 gram CO2 cylinder). To match it with the actual 5.56mm military version I have also equipped it with the Sig Sauer Bravo4 4x30mm Battle Sight. The Sig Sauer optic is the same used by military and law enforcement and costs considerably more than the air rifle it is mounted on, but if you have the MPX civilian version, the Bravo4 is absolutely the first choice for optics, as it was built for the MPX and MCX air rifles. Throughout this series of articles we will also be reviewing other optics designed for CO2-powered air rifles, but for this first installment I decided to show just how authentic this new Sig Sauer CO2 model can be, and look.
When I say “new” the Sig Sauer MPX and MCX are among the latest military rifles, having been introduced late in 2014. Selective fire versions were developed for military and law enforcement, as well as semi-auto civilian models. The MPX and MCX were designed to be the most modern and adaptable (modular) military rifles available; light in weight at around 6 pounds (the CO2 version comes in at 6 pounds, 10.5 ounces with the suppressor shrouded 21-inch barrel), and has the same lean profile for ease of balance and quick handling in close quarters. The MPX has a 16-inch barrel making it a CO2 version of the Sig Sauer SBR (Short Barrel Rifle) model.
If there was one end result Sig Sauer was seeking with its design for the MPX and MCX, it was a modern day version of its legendary (and still in use) MP5 versions. The rifles were developed for use by Spec Ops and offered to U.S. Special Forces. They were first chambered in .300 Blackout, then in 7.62x39mm and the 5.56x45mm NATO round used in the M4A1 (among other battle rifles in use today by U.S. forces). The U.S. military has not yet adopted the MCX (currently that role is filled by Heckler & Koch’s HK416) and there are still on going developmental changes, including modifications to the bolt carrier group on all current models (a mandatory recall and replacement) and for new production models as a safety upgrade. One can recall the many issues that plagued the M16 when it was first introduced more than 50 years ago, and today it is the foundation for the majority of military and law enforcement rifles, including the Sig Sauer. The HK MCX and MPX are much further along in just their first couple of years than the AR platform was after a decade.
In operation the cartridge-firing MCX and MPX are modular AR hybrids with a short-stroke gas piston design that eliminates the need for a buffer and gas tube; in their place Sig uses a compact recoil system contained completely within the upper receiver, making the rifles more compact with a lightweight tubular stock that can be folded alongside the receiver. For the CO2 versions the Sig design creates a simple, integrated shoulder stock tube to surround an 88 gram gas cylinder, which provides the air rifles with up to 700 fps velocities for 4.5mm lead pellets. This is combined with high-capacity 30-round magazines which operate on a unique rotary internal belt. The pellet magazines look like short (10-round) AR mags.
Externally, the airguns have very similar lines and use the same lightweight skeletonized KeyMod-style handguards. KeyMod handguards are designed with different inner diameters so that they can fit over barrels or sound suppressors as needed. The longer handguard design (as seen on the MCX) acts as a continuation of the one-piece top rail, giving you over 15 inches of accessory rail on the CO2 models. The KeyMod handguards will also accept a variety of accessories including the vertical foregrip that comes with the CO2 model, as well as mounting tactical lights and lasers. On the cartridge models the handguards are designed for quick removal and the Sig uppers can be quickly switched out for different barrel lengths, calibers, and accessories in the field. A bit much for a CO2 version to adopt, so the airguns are standard configurations of the two Sig models, the MPX and suppressed MCX (once again a visual not a functional feature on the CO2 model).
On the cartridge models the fire controls are ambidextrous; safety selector, extended magazine release buttons. and charging handle. On the MCX model, the bolt release is only available on one side of the gun, whereas it is ambidextrous on the MPX. All of this is nice to know but little translates to the air rifle as all of the controls, except for the ambidextrous safety, charging handle, and right side magazine release are functional, the rest are meticulously molded into the receiver and magazine well to look 100 percent real, but not function. Other inert features are the ejection port cover, forward assist and disassembly pins. The flip up front and rear BUIS are fully adjustable and more than adequate for the range of the CO2 model, however, it is optics that really make this new Sig Sauer 88 gram CO2 model perform.
In Part 2 we will review the Sig’s unique belt-fed pellet magazine, explore the Sig Sauer Bravo4 on the CO2 model, as well as other more affordable optics that work well with the MCX platform.