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Sig Sauer MCX 5.56

You may have been hiding under a rock if you’ve not heard of the new Sig Sauer MCX Spear, the MCX family of rifles has been a popular stalwart in the Sig Sauer lineup for some time. The industry giant has been bringing all kinds of developments over the decades they have been manufacturing firearms, and the MCX is one of them. At a glance, the MCX appears to be just an AR-15, but a deeper look into the rifle will show something quite different.

The Dawn of Modern Sporting rifles

Since the first Stoner variant of the AR-15, a buffer tube protruding from the rear of the lower receiver has long been commonplace. The buffer tube serves two purposes; first it houses the buffer and spring which are vital parts of the function of the action, and second it serves as the base structure for the buttstock of the firearm. Buttstocks are typically attached around or to the buffer tube itself, which has dominated the design of all the various available buttstocks for AR patterned rifles.
The design of the MCX migrated the buffer spring and its associated hardware into the upper receiver, an in doing so has changed several aspects of the platform itself. Gone are the days of fitting your buttstock to the tube, in fact, you don’t even need a stock with the MCX. There are “pistol” configurations that don’t even utilize a buttstock.
This tubeless design makes the MCX stand out from the AR crowd, but there is more to this gun than just the buttstock.

The MCX

The MCX shares a great deal of parts with most AR-15 style rifles. Magazines, triggers, and such are compatible, but there are also plenty of differences. The bolt carrier in the MCX is driven forward by a pair of springs that ride just above the carrier inside the receiver. The charging handle also sandwiches into the same area as the recoil springs and bolt carrier. The handguard is attached to the upper receiver and features a very skeletonized keymod attachment section, newer models also have MLok compatible handguards. There is a small window in the front of the handguard to access the two-position gas valve.

Bolt carrier and receivers detail

The lower receiver is very similar to traditional AR lowers except where the buttstock attaches, and additionally features an extra magazine release on the left side of the receiver. There is also a small spring plunger mounted behind the trigger, it appears to be an accurizing add-on to reduce the play between upper and lower receivers. The buttstock itself is a skeletonized design with a built in folding hinge allowing the stock to be stowed to the side of the rifle, this of course doesn’t effect the operation of the rifle. All the mechanics of the operating system are contained within the receivers, so the rifle can fire regardless of the stock position.

Rangetime
As soon as I could, I prepared the MCX for the range. I mounted up a fresh Tango MSR scope also from Sig Sauer, the 1-8 power scope would be an excellent compliment to the MCX. I also grabbed a suppressor because I wanted to see how the rifle functioned suppressed. I packed up some PMC Xtac 55 grain ball ammo to shoot in the rifle, as well as a Magpul MS4 sling to use on the rifle. I also brought a couple assorted P-mags and GI magazines to try in the rifle.

After boresighting the scope, I cracked off the first few rounds and they were quite close to my point of aim. It only took minor adjustments to get the scope zeroed and then it was go time. Shooting the rifle at a hundred yards I quickly gained familiarity with both the rifle and scope, hits came easily as the MCX churned away smoothly. The weight felt surprisingly light, I believe they were advertised at six pounds though I think that is a little under what this one weighed naked.
The three-pronged flash hider seemed very effective at reducing muzzle flash, and the recoil of the 5.56 cartridge is very easy to handle in a rifle this size. The rifle was very comfortable in maneuvering and made for a very enjoyable time spending my money. I stretched the rifle out to the three-hundred yard line where I found it to be still quite accurate, I imagined an errant coyote who might have wandered into range would have been easily dispatched.
Shooting from P-mags and GI metal mags both functioned flawlessly as I would expect from this rifle, I figured it was time to install my suppressor to see how the rifle performed suppressed. This required removing the factory flash hider, and installing my suppressor mount. Sig uses a taper on many of their muzzle devices to aid in alignment, since I wasn’t using a Sig suppressor the taper was unneeded. I mounted up my Yankee Hill Machine Turbo 556 suppressor and went right back to town on the targets.

note handguard and gas valve detail

Suppressed shooting made the MCX really shine. The increased weight seemed to calm down the recoil impulse even further making it easy enough to spot my own hits at 200 yards. The reduced noise is always welcome, and hearing steel targets ring without hearing protection is always better.
Accuracy
Accuracy shown here from the MCX wasn’t spectacular, but I can certainly explain that. The included picture shows five shots from 55 grain PMC Xtac ammunition, it shot much better with Hornady Black 75 gr match but I didn’t get it on paper. Shooting from bags at one-hundred yards with an eight-power scope shivering in below freezing temps may not have given the MCX a fair shake. Continue Reading Here…