While SIG Sauer’s 6.8x51mm XM7 is raising eyebrows, their new MCX-Spear LT is what many are more interested in. But how does it perform? (Photo by Sean Utley)
October 03, 2023
By David M. Fortier, Executive Editor
Advances in fighting rifles, their ammunition, optics and accessories seem to come in spurts. Periods of stagnation are followed by periods of great advancements. Technology, materials and manufacturing steadily improve as do methods and techniques for employment. Typically, progress is slow during peacetime but moves at a rapid rate during times of war. One of the most modern designs recently adopted by the US military is SIG Sauer’s XM7 6.8x51mm rifle. This interesting new design was developed for the US Army’s Next Generation Squad Weapon Program as a replacement for their legacy 5.56x45mm M4A1 carbine. A member of SIG Sauer’s MCX Spear family, both the XM7 and its 6.8x51mm cartridge are raising eyebrows. This is due to its features, caliber, and what many perceive is a return to the “battle rifle” concept.
An evolution of SIG Sauer’s MCX and Virtus families, the new MCX-Spear LT was designed to incorporate the best features of the AR-15, into a more modern platform. As interesting as the XM7 and its 6.8x51mm cartridge are though, they are not my focus here. Actually, I’m more interested in a close relative of the XM7, one which is catching many people’s attention. This is SIG Sauer’s 5.56x45mm MCX-Spear LT . The MCX-Spear LT is actually an entire family of weapons chambered for 5.56x45mm, 300 AAC Blackout and 7.62x39mm. The family consists of rifles, pistols and Short Barrel Rifles with barrel lengths of nine, 11, and 16 inches. An evolution of SIG Sauer’s MCX and Virtus families, the new MCX-Spear LT was designed to incorporate the best features of the AR-15, into a more modern platform. The new design would keep the AR-15’s general layout, but optimize it for use with a sound suppressor, modern optics and mission essential accessories, while providing a folding stock. Modularity is important today, and so the end-user can swap stocks, handguards and barrels/calibers to best meet his needs. Plus, due to optics and accessories adding noticeable weight, the MCX-Spear LT was designed to be lighter, better balanced, and quicker handling than the older Virtus. The end result is a family of firearms with some very appealing features.
I am going to ignore how the MCX-Spear LT was developed to meet the needs of certain military and LE end-users and approach this review from the point of view of your average armed citizen. Questions I’d like answered include: Why should I consider a SIG Sauer MCX-Spear LT? What does it really bring to the table? Does it really offer anything substantial over its competitors? Most importantly, is it worth your hard earned money? The best place to start a journey is always at the beginning, so let’s start by examining the rifle itself. I selected the MCX-Spear LT in its 16-inch 5.56x45mm configuration for review. I selected this model over the 300 AAC Blackout and 7.62x39mm chamberings for a number of reasons. These include 5.56x45mm ammunition’s availability, cost, weight, low recoil impulse, accuracy, range, terminal performance and diverse loadings. If subsonic use was a primary concern I would consider 300 AAC Blackout or 7.62x39mm. Each of these calibers has certain advantages, but for my personal needs the 5.56x45mm is the better option.
Why a 16-inch barrel instead of a shorter SBR length? While Short Barrel Rifles certainly excel at certain things, a 16-inch barrel facilitates easy inter-state travel with no NFA paperwork. Plus, the longer barrel provides a noticeably higher muzzle velocity which leads to improved terminal performance and a longer effective range. It also reduces muzzle blast and flash compared to a shorter barrel. When it comes to overall length, folding the stock on the MCX-Spear LT makes it 1.5 inches shorter than my 11.5 inch barreled AR-15 SBR with its stock fully collapsed. Downside? If a sound suppressor is mounted the length becomes fairly long which affects handling.
A Breakdown of the Design Modularity is important today, and so the end-user can swap stocks, handguards and barrels/calibers to best meet his needs. The MCX-Spear LT was designed to be lighter, better balanced and quicker handling than the older Virtus. The MCX-Spear LT’s method of operation is gas via a short-stroke piston. Like many modern piston designs, it is similar conceptually to an AR-18. The gas block has two positions for Normal and Adverse conditions and facilitates both unsuppressed and suppressed firing. The piston system operates a carrier controlled rotating multi-lug bolt. Take down of the bolt carrier assembly is straight-forward and anyone who has stripped an AR-15, or any AR-18-based design, will find it familiar. The bolt carrier assembly rides inside an aluminum upper receiver. This has an extended MIL STD 1913 rail machined into the top for easy mounting of iron sights and day/night optical sights. Ejection is out a port on the right side of the receiver and this is sealed by a spring-loaded door. Behind the ejection port is a brass deflector and a forward assist. An AR-15-style ambidextrous charging handle is mounted. The handguard features numerous slots to reduce weight. For mounting accessories M-LOK slots are provided at 3, 6 and 9 o’clock. There is a MIL STD 1913 rail along its top along with cut-outs on the side for adjusting the gas system. Note, the 1913 rail on top of the upper receiver is approximately 11.5 inches long and extends much further forward compared to a standard AR-15. This provides plenty of room for mounting optical and iron sights onto the receiver itself.
But what about mounting aiming devices onto the handguard itself? Will they actually retain zero? To reduce movement of the handguard, it slides into grooves machined into the receiver. Then it mates up with the front pivot pin point. Lastly, two tension screws bolt the handguard into place. The design is intended to reduce any deflection of the handguard. It’s also easily removed, so it can be swapped for a different length if you are changing barrel lengths. Inside the handguard is a 16-inch cold hammer forged barrel with a Nitride finish and one turn in seven inches rifling twist. Muzzle threads are 1/2x28 TPI and SIG Sauer fits the MCX-Spear LT with their Rocksett QD suppressor-ready flash suppressor. This is a three-prong design and intended to provide effective flash suppression while also acting as QD suppressor mount. The design is intended to seal and isolate the suppressor mounting surface from carbon buildup, to ensure installing/removing a suppressor is always easy and trouble-free. The upper receiver is designed to allow easy removal of the barrel. The barrel is locked into the receiver by two retainers with tapered edges which draw the barrel extension tight into the receiver as two screws are torqued down. So, barrel and caliber changes are not difficult for the end-user.
The operating system is similar in concept to an AR-18. The MCX-Spear LT’s lower receiver is similar to an AR-15 lower receiver and is machined from aluminum. The most obvious difference is the lack of a
An enlarged trigger guard allows easy operation with gloves. SIG Sauer’s Flatblade Match trigger is included. It should be noted though that the MCX-Spear LT is compatible with standard AR-15 triggers as well as SIG Sauer MCX Virtus triggers. The nicely contoured pistol grip features a storage compartment for small items. Lastly, the rear of the lower receiver features two non-rotating QD sling mounting points. Overall length of the rifle, with the stock extended, is only 34.5 inches. Folding the stock reduces the length to a compact 26.5 inches. The MCX-Spear LT weighs just 7.5 pounds and comes with a Coyote finish.
In the Hands The Spear LT is a robust and reliable design intended for professional use. Muzzle threads are 1/2x28 TPI and SIG Sauer fits the MCX-Spear LT with their Rocksett QD suppressor-ready flash suppressor (top right). On the right side of the receiver is a short ambi-safety, magazine release and a bolt catch lever. The right-side bolt catch can be used to lock the bolt back and release it. During my initial examination, I noted the SIG Sauer MCX-Spear LT feels good in the hands. It is well-balanced which makes it feel even lighter than it actually is. It is fast to the shoulder, swings quickly and handles well. While subjective, I found the MCX-Spear LT to be a comfortable and good feeling piece. I like its feel, balance, length of pull, and weight much better than say FN’s SCAR 16S, IWI’s Tavor, and Springfield Armory’s Hellion. The MCX-Spear LT’s controls are very well laid-out, easy to reach, and manipulate. The stock folds easily with the push of a button, yet is rapid to deploy. Folding the stock greatly reduces the overall length for storage or use in and around vehicles. Another useful feature is the ability to lock the bolt back while maintaining a firing grip. This is very handy if you need to clear certain malfunctions. I also greatly prefer the AR-15-style charging handle compared to a forward mounted design, such as on a SCAR, which invariably is in close proximity to your optic mount. I also appreciate how this model was designed with modern accessories in mind. Using this rifle with a sound suppressor wasn’t an afterthought. It was specifically designed with suppressed use in mind. When used with a suppressor fouling and carbon build-up in the receiver will be greatly reduced compared to a standard direct gas AR-15. Mounting white lights, IR lasers/illuminators, optical sights and slings is simple.
Checking Accuracy For the accuracy portion of testing, I mounted a Vortex 6-36x56mm Razor HD Gen III scope using a Geissele Super Precision 34mm mount. The big Vortex is an impressive optic. The new Razor’s magnification zooms all the way to 36X on the top end, while zooming out to just 6X on the low end. The turrets are big, easy to zero and feature .1 Mil adjustments with 10 Mils per full turret rotation. The adjustments are precise with distinct audible and tactile clicks. An external rotation indicator provides both visual and tactile reference of which rotation the turret is on. The design features locking turrets, a smooth operating mechanism block mounted parallax adjustment and an illuminated reticle. This particular scope was fitted with the EBR-7D reticle design delineated in Mils. A first focal plane design, the reticle sports a very fine center dot and hold points for elevation and windage/lead. All in all this is a workhorse of a scope which has become my favorite for accuracy testing.
The stock is basic, rugged and works well. It locks solidly into place yet folds easily for storage. On the left-hand side of the lower receiver, you’ll find an extended bolt release, ambidextrous magazine release and safety. Initial testing was done from the bench at 100 yards with six loads ranging in weight from 55 to 77 grains. Four consecutive five-round groups fired with each load. Test ammunition consisted of Australian Outback’s .223 Rem 55-grain Blitzking load, Black Hills Ammunition’s .223 Rem 69-grain Matchking, 77-grain OTM and their well-respected 5.56x45mm 77-grain Tipped Matchking match loads, Speer’s .223 Rem 75-grain Gold Dot load, and Winchester’s .223 Rem 60-grain PDX-1 Defender. Velocity readings were recorded 12 feet from the muzzle with a LabRadar Doppler chronograph at an ambient temperature of 95 degrees F at 1,130 feet above Sea Level. The rifle zeroed easily and I was soon firing for record. I quickly noticed a few things. It’s a very comfortable rifle to fire. The trigger, while excellent for a service rifle is not a match trigger. It is definitely quite usable and I shot some very good groups with it, but something like a Geissele match trigger would be an improvement. The rifle fed smoothly and extracted easily. Ejection ranged from 2 to 3 o’clock depending upon the load.
I have to say I shot some very good groups. My two best five-shot 100-yard groups of the day measured just .6 of an inch. One was posted with Australian Outback’s 55-grain Blitzking load, which averaged .9 inch at 2,919 fps, and the other with Black Hills Ammunition’s 77-grain OTM, which averaged .9 inch at 2,717 fps. So, the MCX-Spear LT was not fussy about bullet weight. It was fussy about which loads it preferred though. Black Hills Ammunition’s 77-grain TMK load posted a best of .75 inch and averaged 1.2 inches at 2,784 fps while their 69-grain Matchking load averaged 1.8 inches at 2,733 fps. Winchester’s 60-grain PDX-1 Defender load averaged two inches at 2,938 fps while Speer’s 75-grain Gold Dot load averaged 2.4 inches. Overall, I felt accuracy to be quite good for a 7.5-pound semi-automatic rifle.
Up Close with a SIG Sauer ROMEO4XT-PRO Red Dot Stripping the rifle is straight-forward, and it’s a refined design. Stripping the big Vortex off, I next mounted a SIG Sauer ROMEO4XT-PRO Red Dot and ran some drills from seven to 280 yards. This model Red Dot is an evolution of the popular ROMEO4T. A compact design similar in size to Aimpoint’s popular T-2, the ROMEO4XT-PRO is a very robust design. It features top mounted controls for easy manipulation with either hand, is powered by an AAA battery which provides 50,000 hours of runtime and can be used for passive aiming with night vision. Plus, you can switch between four reticles: Dot, Circle and Dot, Dot with BDC points and Circle and Dot with BDC points. So, you can make effective use of a magnifier mounted behind it. It is IPXB-8 rated for waterproof and fog proof performance.
Running drills with the MCX-Spear LT proved a lot of fun. Controllability on rapid fire proved very good with a recoil pulse different than a standard 16-inch AR carbine. Magazines ejected cleanly and the MCX-Spear LT’s controls proved easy to manipulate. Reliability was excellent with no issues encountered. The trigger proved an aid to accuracy and making quick follow-up shots. The MCX-Spear LT proved easily capable of routinely hitting a full-size Action Target silhouette at 230 and 280 yards from various field positions. I shot it offhand, kneeling, sitting and prone. Shooting prone off the mag at this distance simply rang the steel in rapid succession. Thirty rounds of Black Hills 69-grain Matchking match fired at a rapid rate prone off the mag all grouped into the center of the silhouette’s chest.
Bench testing was done at 100 yards. A Vortex 6-36x56mm Razor HD Gen III scope was mounted for bench testing using a Geissele Super Precision 34mm mount . I also ran some drills at night using white light, passively aiming through the ROMEO4XT-PRO using a head mounted PVS-14 night vision monocular, and actively aiming using a Steiner D-BAL IR laser/illuminator. The MCX-Spear LT performed well through-out these drills. Shooting passively with a Red Dot really separates the great red dots from the rest. Simply have a “Night Vision” setting does not make a Red Dot suitable for passive aiming with night vision. Many, due to lower quality lenses and lens coatings, are difficult to see through with night vision. The image through the red dot can be much dimmer, or even black, compared to the rest of the image through your night vision device. Here the ROMEO4XT-PRO did very well and its overall performance impressed me. Watch for a full review of this optic coming soon.
Final Thoughts Australian Outback’s 55-grain Blitzking load posted some nice five-shot 100-yard groups (top left). Black Hills’ 77-grain TMK load also shot well. Practical accuracy out to 280 yards was very good (right).Without a doubt, SIG Sauer’s MCX-Spear LT is an interesting design. Accuracy was excellent for a rack grade service type rifle. The controls are well-designed and I really like the right side bolt release. M-LOK slots and the M1913 rail allow a variety of accessories to be easily mounted. The folding stock is a real asset. Reliability was excellent, and zero issues or malfunctions of any type were encountered. Finally, field stripping the MCX-Spear LT is straight-forward. Downside is the price. The MSRP is fairly steep at $2,729. So, it is priced similar to other high end semi-auto rifles intended for professional use. Overall, SIG Sauer’s MCX-Spear LT is a well-thought-out and refined design. It’s robust, nicely made and invokes pride in ownership. For use in and around motor vehicles the side-folding stock is a real asset. For use with a sound suppressor the operating system is an asset. Depending upon your needs the design’s modularity can be an advantage. It brings a lot to the table for the armed professional as well as the armed citizen. I like it, but only you can decide if you have any need for its features and what it provides.
Accuracy Data SIG Sauer MCX-Spear LT Operation: Short-stroke gas with rotating boltCaliber: 5.56x45mm NATOBarrel: 16 in., cold-hammer-forged with Nitride finish with 1:7-in. twistFeed: STANAG compatible AR-15 type detachable 30-rd. box magazineWeight: 7.5 lbs. without magazineTrigger: 2-stage with 4-lb. pullOverall Length: 34.5 in. with stock fully extended, 26.5 in. with stock foldedLength of Pull: 12.5 in. Sights: NonePrice: $2,729Manufacturer: SIG Sauer About the Author David M. Fortier has been covering firearms, ammunition and optics since 1998. He is a recipient of the Carl Zeiss Outdoor Writer of the Year award and his writing has been recognized by the Civil Rights organization JPFO. In 2007, he covered the war in Iraq as an embedded journalist. He has written extensively on opposing forces small arms, ammunition and optics and has traveled through Russia, Europe, the Middle East, and South America. His writing has been translated into both Russian and Mandarin. He was a regular on the Outdoor Sportsman Group’s network television from 2003 to 2020. He is currently the Editor of the Outdoor Sportsman Group prepping title Be Ready! magazine, as well as the Executive Editor of Firearms News. Prior to 1998, he was in the Aerospace and Defense industry.
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