Developed around 5-years ago, the KeyMod looks like a series of keyholes into which any accessory with a machined mounting screw and nut or (two or more) can attach and be solidly locked into place. The centerfire Sig Sauer MCX model uses a KeyMod system handguard which is designed for the rapid mounting and dismounting of accessories and accessory rails. It comes from the factory with the foregrip positioned to the rear and closer to the magwell as shown. Both the centerfire and CO2 pellet models use a KeyMod accessory handguard which makes fitting of accessories simple and quick to mount. But if you have longer arms it could be too close. I found the factory mounting position good because it is far enough back that it helps push the support arm into the body for a more solid hold. It has a foregrip that comes mounted to the handguard and for some it is positioned too far back on the handguard rail. It’s Thanksgiving and so this is going to be a short read, but one that answers a very good question about the Sig Sauer MCX CO2 semi-auto tactical rifle.
Also pictured are a Sig Sauer P226 CO2 pistol in FDE (holstered) and a Surefire Luminox 2211 tactical light combat watch. The CO2 model shown is fitted with the actual Sig Sauer Bravo 4 Battle Sight used on the centerfire 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. 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. KeyMod handguards are designed with different inner diameters so that they can fit over barrels or sound suppressors as needed. Sig Sauer MCX and KeyMod System Making a change to accessories By Dennis Adler The Sig Sauer MCX airguns have very similar lines and use the same lightweight KeyMod-style handguards as the centerfire models.