Lima SIX Belt-Fed AR: ‘Merica In Every Sense Of The Word

It’s Sunday Night Football, under the big lights with the division title in play. It’s 3rd and 8, and the quarterback is rallying the offense to make a final push in the fourth quarter. The roar in the stadium is nearly deafening as the crowd howls for the home team. A voice in the quarterback’s ear lights up — “Watch out for middle cross dog. Double slant right 32.” It’s his coach, using the official coach-to-player headset to give him advice and call the play. 

That wireless headset system was created by Harvey Shuhart Jr. and deployed throughout the National Football League back in 1994. An engineer, Shuhart Jr. designed and invented many electrical devices and systems throughout his long career. Unfortunately, he passed away unexpectedly in 2023. 

At that point, he had scaled down his business and was a one-man shop. His son, Harvey Shuhart III, had a job doing manufacturing engineering at a metal fabrication shop. He stepped into his dad’s business to finish up some ongoing communications contracts but concluded that the business was no longer sustainable. He had a tough choice — shut it down or pivot into something else.

Shuhart had always been very passionate about guns and building things. In particular, he had always wanted to build a belt-fed. No time like the present, so he got to work. And he chose the brand Lima Six in honor of his father, who was an avid pilot and had the designation “L-6” on his airplane hangar.

BELT-FED SUPREMACY

Fire superiority is a crucial element in military tactics — whatever volume of fire the enemy is sending your way, you want to deliver even more back in their direction. If you’re successful in this effort, then the enemy’s resources will deteriorate. As this happens, your advantage will grow and grow until you’ve defeated the enemy.

Machine guns are a vital tool for achieving fire superiority, as they can output high rates of fire for long periods of time. Magazines have limited capacity, so these systems feed from long belts of ammunition to keep rounds flowing downrange.

Historically, these weapons were large, heavy, and crew-served. Scaling them down and chambering them in 5.56 NATO resulted in Squad Automatic Weapons like the M249 that can be fielded by a single individual.

These light machine guns operate with an open-bolt system, where the chamber is empty and the bolt retracted when ready to fire. Press the trigger and the bolt is released, stripping a round from the belt, chambering it, and firing the round. It’ll keep going until you come off the trigger or reach the end of your belt. Additionally, the quick-change barrel is easy to swap out, in case it overheats with sustained fire.

Unfortunately, as you can imagine, you won’t find a lot of military-issue-style belt-feds at your local gun store, and FN’s badass civilian version of the M249 has a stratospheric price tag (see RECOIL Issue 72).

TAKING THE BELT TO AN AR

With such high cost and complexity of those bespoke belt-feds, it’s natural to look to the AR platform as an alternative. However, there are some challenges, even putting aside legal restrictions on open-bolt guns. Belt-feds have a lot of work to do between each shot, not to mention dealing with high rates of fire, heat, carbon, and debris. They typically have stout operating systems with lots of gas, spring tension, and mass. Moreover, the AR platform was designed with a short operating stroke, which doesn’t help with reliable feeding. It’s fine for a magazine-fed semi-auto and works in full-auto but the operating window narrows.

Indeed, it’s taken a long time. In the 1990s, Ares Defense began work on the Shrike belt-fed upper, eventually becoming FightLite Industries and releasing the MCR system in 2017. It’s a gas-piston upper with a quick-change barrel that sits on a standard AR lower and feeds from a belt or a magazine. However, the upper retails for $7,000, so it’s still quite pricey; they’ve since come out with the DFX, which is $3,000 less and has fewer features, with a fixed barrel and non-adjustable gas system.

LIVING THE DREAM

Meanwhile, visions of belts danced in Shuhart’s head. His design objective was to build a practical, reliable belt-fed upper that could be more attainable for more people. He wanted to use as many standard components as possible, not just to control costs but for simplicity and parts commonality. He also decided that sticking with a fixed barrel made sense for all of these reasons and was a worthwhile compromise. It took him six months to develop his first prototype, and he’s kept a running open dialogue with users on the AR15.com forum in a thread that’s now 88 pages long.

His most significant big brain moment was his decision to stretch the upper. By extending the front of the upper further forward, he gained an additional 23 percent of travel for the bolt carrier group. A standard AR doesn’t have much leeway after bottoming out the BCG. Belts have a lot of friction in the links and weight from the belt, so they rob energy, typically requiring stiff springs and lots of gas — not to mention potential ammo restrictions. There’s about 3/4 inch of additional travel in the Lima Six, widening the operating window for reliable operation.

This requires more room on the ass end of the gun, so if you have a carbine-length receiver extension on your lower, you’ll need to run an AR-10 buffer (at 2.5 inches, it’s shorter than an AR-15 buffer). With the longer A5 receiver extension, run a standard length AR-15 buffer. And with a rifle-length tube, run an AR-10 rifle buffer, which is shorter than an AR-15 rifle buffer.

Lima Six retains the standard AR’s gas impingement system, but with the feed mechanism and top cover, the gas system needed to be relocated. It’s rotated to the left at the 9 o’clock position, so while standard handguards can be used, they must clear the gas block and tube on the side and the barrel nut must allow the tube to pass. A number of existing handguards work with a standard gas block and tube, while only a few are compatible with the excellent Riflespeed gas block and straight gas tube. Complete uppers come with a Midwest Industries quad-rail handguard specifically customized for the system.

The Lima Six takes standard AR barrels and extensions, but a new gas port must be drilled; the company offers a jig if you’re the DIY type. When installed, the barrel is rotated about 67.5 degrees, putting one of the two feed ramps at 12 o’clock. Because the system doesn’t feed from staggered double-stack magazines, the second feed ramp goes unused; no need for proprietary bolts or barrel extensions.

The company insists on heavy profiles for barrels, shipping complete uppers with an 18-inch barrel that’s a hefty 1 inch under the handguard and 0.75 inches in front of the gas block. Made of 4150 CMV, it has a mid-length gas system and is chrome-lined with a phosphate outer finish.

The upper receiver has a hinged top cover with a latch button at the rear to open it. Take a closer look at the button, and you’ll realize that they used a standard AR magazine release. On the underside of the top cover is the feed lever, feed pawl assembly, and cartridge guides. Below it is the feed tray as well as the charging handle and feed stud attached to the bolt carrier group underneath.

Lima Six is also very proud of the top cover design. The hinge features user-adjustable tension; it has two knuckles each on the cover and the upper, with a precision ground shoulder bolt and bronze bushings between all the joints. When you tighten the bolt, it pulls the two pieces together to your desired amount of tension, so the top cover moves as smoothly as you like and can stay in place when you let go. The latch assembly snaps into place with two points of engagement and a set screw to eliminate any slack. This ensures solid, consistent lockup for precision from optics mounted on the top Picatinny rail on the cover and return to zero when opening and closing it. We put this to the test; more on this later.

The feeding mechanism is inspired by the M249’s design. Feed trays are expensive to manufacture, so Lima Six optimized theirs for better manufacturing efficiency. It feeds from standard M27 links and M249 boxes and nutsacks, using a magwell adapter with an M249 dovetail.

You can mount the Lima Six upper on standard AR-15 lower receivers; you need to swap out the bolt catch since the upper is so wide, and you need to configure the buffer and tube as described earlier. There’s also a gap at the rear of the upper where you need to insert the provided receiver plug, to prevent excess gas from spraying into your face.

Attaching a 200-round ammo box to a magwell adapter elevates the weapon quite a lot. An even nicer option is a lower specifically designed for the Lima Six. At press time, Inoculum Group and Black Widow Arms both make lowers that precisely fit the outsized upper, delete the magwell, add a high- and forward-mounted M249 dovetail, modify bolt catches, and let dropped links fall free through cutouts. 

Additionally, Hydra Weaponry makes a dedicated Lima Six attachment for their clever Hydra lowers with interchangeable magwells. Because the Hydra is otherwise a standard AR lower, it doesn’t exactly match up with the belt-fed upper’s contours. Of course, it provides the flexibility to swap out magwells — the reason you got a Hydra in the first place.

In total, the Lima Six uses AR components for the barrel, lower receiver, gas block, gas tube, gas key, handguard, extractor, ejector, springs, and cam pin.

An ecosystem is also forming around the Lima Six system, with Shuhart’s full support. Various companies are developing not just dedicated lowers but quick-change barrel systems, gas piston conversions, heat sinks, and more.

MANUAL OF ARMS

Operating the Lima Six should be pretty straightforward to anyone who’s spent time behind other belt-feds. To load it, first place it on safe and lock the bolt back; it must be locked back to load the weapon. Note that the charging handle reciprocates with the bolt. Machine gunners will remind you to grasp the handle with the palm facing upward so that your thumb isn’t behind it, just in case.

Remember the old adage: brass to the grass. With the exposed brass facing downward, pull the belt across the feed tray and place the first round against the cartridge stop. Hold the belt in place and close the feed tray; you can go hands-free if you have a starter tab on your belt. Note that the bolt must be locked back to close the top cover. Retract and release the charging handle to chamber a round, and you’re good to go. Keep in mind with a closed-bolt system, there’s always a risk of cook-offs if you get the gun stupid hot.

Besides your ammunition choice and a suppressor, key elements to tune your Lima Six for reliable operation include the amount of gas, buffer weight, and buffer spring. The complete upper comes with an adjustable Riflespeed gas block, making controlling the amount of gas flow a cinch.

To unload, put the gun on safe, then open the top cover. Remove the belt and police any brass or links that remain. Lock the bolt back and double check the chamber is empty.

Once you’ve verified the weapon is unloaded, you can fieldstrip it. Close the bolt and separate the upper from the lower. Retract the charging handle and remove it (two screws). Hold the bolt carrier to the rear, open the top cover, and remove the feed stud. Then, you can pull the BCG out of the upper and service it like a normal one. Depress the spring-loaded retainer to remove the feed tray. That’s it.

Be sure to clean and lubricate it well before reassembling. Lima Six recommends EWG grease and EWL30 oil by SLIP 2000.

KITTING OUT THE BEAST

The first step in getting the Lima Six ready for the range is prepping the lower. In this case, we had an embarrassment of riches. Firstly, we had an early Hydra Weaponry Hydra 15 modular lower with interchangeable magwells — by sliding off the front of the lower, you can easily switch between supporting different types of magazines. Hydra makes magwells for standard 5.56mm, AK-47, and a variety of PCC and other magazines. They were one of the first to support belt-fed platforms, releasing slim magwells with M249 dovetails for the Lima Six as well as the dual-feed platforms like FightLite and Cloak Industries. As shown here, it works wonderfully; however, our early generation Hydra lower requires modification to work with the AS Designs active reset trigger.

Therefore, we mounted up a dedicated Lima Six lower from Inoculum Group, the latest venture from the same folks who stood up 2A Armament, known for extreme lightweight AR systems like the BALIOS-LITE. They eventually sold that company and are now family owned again and focused on projects they’re passionate about with Inoculum. The IGM7 lower is beautifully machined and matches the Lima Six perfectly. 

While you can use an adapter in a normal lower, run one of these purpose-built lowers and you won’t want to go back. In particular, a regular lower places the gun awkwardly high in prone or off a bench. The Tribe Tactical Supply 100-round nutsack shown here was a perfect size and balances nicely.

In the Inoculum lower lives an AS Designs ARC-Fire v2 trigger. Forced reset triggers really take belt-fed platforms to the next level. See the sidebar for more on the trigger — TLDR, it was awesome.

We finished off the lower with an A5 receiver extension and furniture from Mission First Tactical. Their Engage pistol grip and Battlelink Utility stock provided great ergonomics for this build.

We’re civilized folk, so we spun off the included A2 flash hider and installed a Plan B muzzle device from Wolfpack Armory. The Lima Six is already rather long with its 18-inch barrel, so we attached the stubby and low-blowback Banish Speed K suppressor.

Moving back to the quad-rail handguard, we attached a SureFire Dual Fuel Turbo Scout Light Pro. The 100,000 candela really punches out at distance, while the pivoting integrated mount keeps it tight against the gun. The Holosun IRIS-GR3 takes care of the rest, combining a 520nm green visible laser, 800-880nm Class 1 infrared laser, and 60mW infrared illuminator in one compact package. The lasers are co-aligned for convenient zeroing, and the controls are intuitive. It also comes with a remote switch.

Support is also important, and Spartan Precision Equipment’s new Valhalla Gen 2 bipod is made of aluminum and carbon fiber for great stability and light weight. The quick-detach spigot mount clamps right on the Picatinny handguard, with quick deployment of the legs and extensions.

We can’t help but be a little extra here at RECOIL, so rather than mounting the typical red dot, we reached for Vortex’s AMG 1-10x LPVO. It provides the versatility of a wide magnification range, nuclear bright reticle at 1x, and importantly, a very short overall length that exactly fits on the top cover of the Lima Six. We affixed the scope in Scalarworks’ lightweight bolt-on FUSE/03 mount; it weighs barely over 5 ounces and makes it easy to properly level your scope during installation. A single Magpul XTM rail panel on the handguard protects the scope from banging into the rail.

Finally, Global Ordnance sent us a buttload of Igman 55s and some ADI match ammo to really shake out the Lima Six. On the other hand, we then needed to link all that ammo. Assuming you don’t have industrious small children at your beck and call, another small American company came to the rescue. Niche Tactical’s M27 progressive linker made short work of cranking out belt after belt, for a lot less moolah than industrial linking machines. See the sidebar for more details.

VOLUME BY FIRE

We won’t drag this out — the Lima Six is fantastic. Our first pleasant surprise came while shooting groups and measuring muzzle velocities off the bench with the Spartan Valhalla bipod and a rear bag. Our upper was from an early batch with barrels made by Rosco; current production comes with KAK Industry barrels.

Igman 55-grain FMJ printed 1.5 to 2.6 MOA five-shot groups, at 3,031 fps unsuppressed and 3,057 fps suppressed. Point of impact shifted approximately 2 MOA lower with the can, which we left on for the remainder of testing.

We got roughly 2 MOA groups with Black Hills 55-grain FMJ, at an average of 3,020 fps. It just got better from there.

Federal Gold Medal CenterStrike 77-grain OTM ratcheted it up to 1.4 MOA at 2,556 fps, while ADI 69-grain Sierra MatchKings tightened up to 1.25 MOA at 2,688 fps. And our best group was about 1.2 MOA with Black Hills 77-grain OTM, at 2,704 fps. Hat tip to the Vortex 1-10x, too.

Remember, this is a belt-fed! When opening and closing the top cover, which was tightened snugly, we found point of impact to stay within about 1 MOA. Impressive results, indeed. 

Note that the last round in a belt would typically throw the shot left by around 3 to 5 MOA, so we used six-round belts for all of these groups and discarded the last shot.

Lima Six recommends a break-in period of 200 rounds. In full disclosure, the company said they ran about 50 rounds through our upper, more than in typical production. We settled on an H3 buffer and orange Sprinco spring with maximum gas, and our upper chugged through hundreds and hundreds and hundreds of rounds from 55- to 77-grain, in both semi and very-fast semi modes, without a single malfunction. 

The AS Designs ARC-Fire v2 trigger provided consistent and reliable operation at just under 500 rpm, measured using Double Alpha’s EDGE shot timer cyclic rate feature. Splits typically ranged between 0.11 to 0.13 seconds. It’s a useful, controllable rate of fire, like having Jerry Miculek on tap. It was easy to rip off three- to five-round bursts. A Mil-spec trigger, it was gritty but broke consistently at around 5 pounds.

The system has a long dwell time; along with the extended stroke and buffer setup, it had a very smooth recoil impulse. The entire system as shown here weighs a hefty 14 pounds, unloaded; a 100-round nutsack adds another 3.4 pounds. We could keep sustained 15-round bursts almost entirely in the A zone at 10 to 15 yards.

AS DESIGNS ARC-FIRE TRIGGER V2

Semi-automatic firearms discharge a single round with each press of the trigger. When you release pressure on the trigger, it moves forward and resets for the next shot. Generally speaking, forced reset trigger mechanisms use the cycling action of the gun to make that reset happen immediately.

Therefore, as you continue to press back on the trigger, it’ll be ready to fire again right away. These systems don’t make your gun cycle any faster, and you’re still actuating the trigger for each shot. But it’s like you have Jerry Miculek on tap to help you work the trigger quickly and reliably, without the typical trigger freeze or jerking the trigger that can often happen when you deliberately try hard to go fast.

AS Designs’ ARC-Fire Trigger V2 is the latest and greatest incarnation of this type of trigger system. They’re available with or without ambidextrous selectors, with a short lever to put on your firing side. But importantly, you can also choose between throw angles for each of the three selector positions — the traditional 0, 90, and 180 degrees; 0, 45, and 180 degrees; or 0, 45, and 90 degrees.

ARC stands for Active Reset Clutch. The detent tracks are smoother and cam surfaces larger, made of M2 tool steel with a DLC coating for smooth, robust, and reliable operation. You can purchase entire kits that come with pre-cut triggers, either standard Mil-spec or even Geissele units for sublime trigger pulls in any mode.

Note that some AR lowers have a high shelf at the rear of the fire control pocket, which can interfere with the ARC-Fire trigger. You’ll need to file down that shelf on these lower.

We tested the ARC-Fire in the Lima Six as well as in a 14.5 mid-length gas BCM rifle. The Lima Six had a H3 buffer with orange Sprinco spring in an A5 receiver extension, while the BCM had an H3 buffer with standard spring. Measured with our Double Alpha EDGE shot timer, the Lima Six ran at 490 rpm and the BCM at 500 rpm with Igman 55-grain ammo. We’re very pleased with this cyclic rate — it’s very practical and controllable.

NICHE TACTICAL PROGRESSIVE LINKER

Belted ammo using metallic disintegrating links utilize curved metal links that hold two rounds of ammo next to each other. When a round is pushed out of its links and fed into the chamber, the link falls away from the belt and is ejected. This continues with each subsequent round. The M27 link is the U.S. and NATO standard for 5.56mm belted ammo. A clever design, but it’s a hassle to assemble links by hand.

Enter the M27 Progressive Linker from Niche Tactical, started by a software engineer who got tired of linking belts by hand. Plate linkers work fine and are inexpensive, but there’s nothing like turning a crank when you need to assemble some serious belts of freedom. Inspired by the Vickers linker design from the 19th century, Niche designed a reciprocating ram and connecting bar to work with metallic links. The linker is a mix of printed components and machined steel for critical areas and components, allowing for a lower price point and reliable operation.

The linker has a vertical magazine for links (20- or 35-link capacity) and a feed tray that holds 20 rounds of ammo. You can swap in an agitated hopper that holds 100 rounds. Loading the links is probably the most annoying part of the process; a weighted follower keeps downward pressure on the links. The feed tray works well but the large hopper allows you to focus on keeping the links going. Place a starter round in the linker, then turn that crank. It’s so easy and very satisfying.

Niche advises that the weight of 30 to 60 rounds on a belt hanging off the loader can cause functioning issues. We found this to indeed be the case, but placed and elevated a box to catch and support the finished belt. As long as we kept an eye on it to keep it stable and aligned, we were able to keep on cranking to fill our 100-round nutsacks. You can always assemble smaller 30- or 40-round segments and then connect them later too.

Niche also makes a long action progressive linker with interchangeable plates for 1919 or M13 links, as well as other linkers and loaders for your belt-fed obsessions.

LOOSE ROUNDS

We absolutely love this thing. And you will too. With match ammo, you can put rounds on target very accurately for as long as the belt allows. And with the third selector position, you can send a lot of rounds downrange very quickly. This makes for a very compelling “civilian automatic rifle” configuration, as long as you can handle the weight.

You needn’t kit it up with all the pricey accessories that we did here. Just get a Lima Six, a dedicated lower if you can swing it, a forced reset trigger, and a ton of ammo and links. Then, put whatever you already have on it. You won’t be disappointed. Alternately, you can roll your own with a DIY build kit. Lima Six is also working on a 12.5-inch version and a big brother in 7.62mm.

Looping back to the origin story, this story is about as ’Merica as ’Merica can be. Shuhart loves belt-feds and legitimately wants to get more belt-feds in the hands of American citizens. From scratch, he’s built the most affordable belt-fed upper on the market, and it works great. It’s made in America, and he’s achieving the American dream in the process. 

He bet his company on this crazy idea, and last we spoke with him, he had five full-time employees, several part-timers and contractors, his mom doing the books, and over 2,000 units sold thus far. Perhaps by the time his son, Harvey Shuhart IV, takes the helm of Lima Six, he’ll be building plasma rifles in the 40-watt range for us all.