There is no “mil-spec” defined for the large frame AR platform, and therefore several versions exist all with slightly different design and dimensions. Fortunately, this allowed for innovation and improvements far beyond the small frame AR mil-spec design.
Lewis Machine and Tool (LMT Defense) has been in business for almost 40 years, focuses on providing rifles and supporting products for the military, law enforcement, and government agencies. This focus along with imagination and ingenuity resulted in the development of the monolithic upper receiver and MARS-H lower receiver on the tested MWS 308/ 6.5 Creedmoor.
The consumer shooting sector is now waking up to all LMT has to offer from the years of development and refinement of high-end firearms. I practically lusted after their SOPMOD stock back in the 1990s when it first came out. Now similar stocks are made by several manufacturers, but then again they have always been ahead of their time.
The Upper Receiver
The patented one-piece monolithic upper receiver which includes the handguard and the quick-change barrel retention system is a machining work of art and reflects a bit of genius. The upper allows the user to change barrels in about one minute. This means the ability to change barrel length, weight, or even calibers (depending on intended use) with only one Torx driver, rather than an entire armorers toolbox.
When you see and feel the fit, finish, and tolerances of the mating surfaces between the upper and barrel, it instills confidence that the entire weapon is going to exceed your expectations.
Rather than merely securing the barrel in place by forcing it back against the front of the upper receiver with the barrel extension loosely fitting within the receiver as done on standard AR designs, the LMT utilizes much greater clamping surface area. The LMT MWS upper clamps down around the barrel with 2 Torx bolts that thread into steel inserts in the other side of the upper.
The bearing surface of the barrel extension is 2.57” long and the upper clamps down around almost the full 360 degrees of the barrel. This results in approximately 10.9 square inches of the surface area holding the barrel in place, far more than standard designs. This design also means 2.5” of locked down alignment of the barrel as well.
In addition, the forward clamping bolt fits through a slot machined in the lower portion of the barrel to properly index the barrel and ensure the barrel is seated properly. If the barrel isn’t fully seated to the rear and indexed properly, the bolt cannot be inserted and tightened.
The large bearing surface, close tolerances, and alignment bolt all help to ensure proper fit when changing barrels. Pausing to think about that for a moment, it also means that the tolerances of all their barrels are also very high.
The monolithic upper is a bit heavier at 33 oz than a standard design and associated handguard, however, it is very rigid and also includes the barrel mounting system so all that must be considered when doing a true comparison.
The rigidity of the free-floated handguard portion of the upper makes it perfect for mounting scopes, dots, bipods, lights, and lasers that you need to be unaffected due to the pressure exerted on it. The rifle length upper has 19.25 inches of Picatinny rail on top for mounting your optics, night vision, etc.
The handguard of the tested upper utilizes the M-Lok mounting system for attaching rail sections or accessories. The fit between the upper and lower is so tight it actually required downward pressure to insert or remove the rear takedown pin. Definitely no rattle or wiggle in this rifle.
The upper features a brass deflector but the extractor and dual ejectors on the LMT bolt throw the brass cleanly from the ejection port so it doesn’t have a mark on it. The upper does not have a forward assist and appears not to need one, as feeding and bolt closure has been 100% during testing.
The bolt and bolt carrier group are plated to keep them hard, slick, and easy to clean. The bolt features twin ejectors for a positive ejection that throws the brass in a nice pile about 10 feet back at your 4 o’clock.
The Lower Receiver
The MARS-H lower is a bit of a work of art itself, even when it is mounted up against something as unique as the LMT monolithic upper. The machining and fit are excellent, as expected, but it’s the functionality that tends to steal the show.
The LMT’s fully ambidextrous controls set a new standard for how all AR platform rifles really should be made. I’ve had guns with Ambi controls before but most had small issues that left tweaks or adjustments to be desired.
The LMT controls just work, and they will change the way you operate and manipulate the gun. It didn’t take any time at all to start fully utilizing the controls. It’s so much more natural to lock back the bolt with the trigger finger while pulling the charging handle back with your support hand; this allows keeping the rifle in a firing grip.
The safeties are just the right size, easy to operate but not so large to interfere with trigger manipulation. The Ambi-magazine release buttons functioned reliably and well as expected.
The LMT trigger is a 2 stage that averages right at 4 ½ lbs. It’s a good weight for a battle rifle, plinker, or hunting. It’s light enough to be shot well and heavy enough to be safe in all environments.
An LMT over-molded grip and enlarged trigger guard make for a secure grip and comfortable operation. The magazine well is generously flared to aid in making rapid reloads.
The LMT SOPMOD stock provides a reliable cheek weld while riding on a dry lube coated 6 position extension tube.
Operating System- Direct Impingement
Length- 38.5” (as tested 20” barrel)
Weight- 10 lbs 2 oz
Trigger- 2 stage
Stock- 6 position
The primary tested barrel was a 20” 6.5 Creedmoor. It was a stainless steel 5R cut 1-8 twist that is cryogenically treated for stress relief. The gas block is pinned in place to ensure alignment and directs gas to the bolt through a straight gas tube.
I also grouped and function tested a 16” 308 barrel and it also exceeded my expectations. Barrels are available in a variety of profiles and lengths from 13.5 inches to 24inches and in 6.5 CM, 7.62, and 7mm-08 calibers. The tested 6.5 barrel weighed 4lbs 2oz making up a bit over 40% of the rifle’s weight. It proved itself well over an extended shooting period in fairly warm southern weather.
With over 500 rounds of 6.5 CM and 200 of 7.62 run through the gun, it has been 100% reliable; no issues feeding, no issues ejecting. Three different magazines were used, loaded with 5, 10 or 20 rounds and never the first hiccup.
I mounted a Nightforce 5-25 ATACR F1 in an NF one-piece mount, went to the range for a solid zero and then was off to Texas for a long-range class. Shooting from a bipod and rear bag in 7-25 mph winds, the LMT punished the steel as long as I did my part on calling the winds. (Kestrels are priceless).
On the second class day at the range, the 6.5CM was getting first shot hits on Accuracy 1ststeel targets out to 942 yards, and second/ third rounds hits out to 1266 yards. There was no handicap shooting a 20” barreled gas gun beyond 1000 yards.
The only drawback to stretching the LMT to those distances was the battle trigger, it’s a good trigger but a bit more challenging than those of the bolt guns on the line. It just takes a bit more discipline and patience when breaking the shot, but it hit every target on the range.
Recoil is noticeable but not unpleasant. It’s in line with what should be expected from a full-sized, full caliber gun with a 19 oz bolt carrier group cycling. Good shooter position and the SOPMOD buttstock make it very controllable and allowed spotting my own hits or misses while shooting.
One-hundred yard group testing from bipod and bag demonstrated that the LMT MWS is a very accurate gas gun. Group after group of Hornady 147 ELD-M’s came in below 1”; while several groups came in at .6” or below. As with the long-range shooting, the trigger and my ability to break every shot cleanly was probably the limiting factor.
In an effort to see how repeatable the barrel mounting system was, I removed the barrel and completely disassembled the gun, even removing the scope from the receiver and then reassembled. The groups after reassembly were .6 mil from the previous point of impact. That is awesome considering that the scope mount is not a true return to zero design.
I removed just the barrel again and again and group shift was a mere .1 to .2 mils off. The surface area and design definitely showed their value.
Everything about the LMT MWS is top shelf: 100% reliable, ambidextrous, outstanding accuracy, 1200 yard capacity, adaptable, and convertible. Modular Weapon System (MWS) is absolutely correct; change your mission, change the stock, change the barrel length, change the caliber.
The MWS exceeded my expectations for accuracy and reliability; 2 barrels, multiple mags, several bullet types and manufacturers, and it never showed any hint of a malfunction or issue. Both barrels shot exceptionally well and the entire platform demonstrated exceptional quality everywhere I looked.