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Guns Long Guns Rifles


by David Fortier   |  November 9th, 2012 16

With the UCIW SIX8, LWRCI ditched the idea of using standard AR-15 components and made a receiver sized specifically for the 6.8mm SPC.

Standing on a private range in Maryland, I watched as Richard King swapped his Nikon for a 16-inch LWRC 6.8x43mm carbine. Racking one of ATK’s new 90-grain 6.8s into the chamber, he acquired a target and put one and then another into the A-zone. Quickly switching targets, he engaged a second and then a third silhouette in rapid succession. His double-taps were lightning fast, yet his hits were perfectly placed.

Lowering the carbine he flashed me a grin and stuttered, “You’ve got to be joking…” before getting back to work. Yes Virginia, LWRCI’s 6.8x43mm rifle is not only shockingly smooth shooting but it also packs an impressive punch. The reaction of the steel targets to the 90-grain slug was ample proof this was no mundane 5.56x45mm.

No, this was an honest-to-God intermediate cartridge developed specifically to provide an increase in terminal performance and penetration. It not only accomplishes its intended mission, but does it with Steve McQueen style.

In my personal opinion the 6.8x43mm Rem. Special Purpose Cartridge (SPC) is one of the great cartridges of our time. This may surprise you, as I’m well known as an outspoken advocate of the 6.5mm Grendel.

It really shouldn’t. Just as I can appreciate equally the .303 British and 7.92x57mm Mauser, so do I admire the performance of both the Grendel and the SPC. Together the 6.5x38mm Grendel and 6.8x43mm SPC have taken intermediate cartridges to a new level of performance. Both of them run roughshod over traditional classics like the 5.56x45mm NATO and 7.62x39mm M43.

More importantly, both have evolved to new levels of performance since introduced in 2004. No firearms company has taken this cartridge as far as has LWRC International of Cambridge, Md. There I got a behind-the-scenes look at both the company and its work in taking the 6.8x43mm Rem SPC cartridge to the next level.

Sitting down with Darren Mellors and Jesse Gomez, I next went over LWRCI’s work with the 6.8x43mm Rem SPC cartridge. “When we started out in the industry we were 7.62x51mm FAL guys,” Mellors started, “So the 5.56x45mm NATO wasn’t what we were used to. The U.S. military had experienced issues with terminal performance with their 62-grain M855 ball load. This issue was intensified by the use of very short barrels.

Very short barrels also increased the rate of fire and often led to reliability problems with conventional 5.56x45mm direct gas ARs. We had the gas piston technology and thought it and the 6.8x43mm cartridge made an excellent combination. Plus we thought the 6.8x43mm would really shine in short barrels. Keep in mind, about this time certain companies were coming out with PDWs (Personal Defense Weapons).”

“Darren had a funny comment on the term PDW,” Gomez said with a chuckle.

“What’s that?” I asked.

“PDW, Popgun Devoid of Whoopass,” Mellors replied. “That’s not what we wanted. We thought we could design and build a very short carbine in 6.8x43mm which would be very useful for urban combat. When you are close enough to stare into the whites of your enemy’s eyes, your weapon system, to include the ammunition, had better immediately arrest the enemy’s ability to do you harm, despite intermediate barriers and body armor.

“So we undertook testing and made barrels in lengths out to 18 inches. We conducted in-depth velocity testing and tested faster burning powders and heavier projectile weights to optimize performance. Unfortunately at this same time, the cartridge was being pushed prematurely by some towards the U.S. military. Pushed very hard. Unfortunately rifles and ammunition were not yet optimized. Even the 6.8x43mm’s chamber print was not optimized. There were issues and eventually the cartridge became toxic with the U.S. military. Some people were looking very monolithically.

“We continued working with the 6.8x43mm SPC because we saw its potential. But we kept running into the same problems over the years. There didn’t really seem to be a standard, especially with the ammunition. One manufacturer would produce ammunition at one velocity and pressure while another would run much faster at a much higher pressure. This created problems with setting the rifles up properly. Plus there were magazine issues. We tried all the available magazines and worked with the manufacturers. But the magazines available were not ideal for hard military use. Eventually we just got frustrated.”

“We knew we could do better,” Gomez kicked in.

A strength, but at the same time a weakness, of the 6.8x43mm cartridge is that it was specifically designed to fit within the confines of the existing 5.56x45mm AR magazine well. This obviously dictated the cartridge’s overall length.

But in practice, it does much more than that. It also limits the magazine wall thickness and in doing so the type of materials which can be utilized to construct magazines.

And because the magazine well width is not optimum for the 6.8x43mm cartridge, rounds do not stack perfectly: they push out against the walls of the magazine more than desired, leading to drag. They also push out on the feed lips, trying to spread them apart.

Another issue is a suppressed full-auto gun can overspeed the magazine’s ability to lift cartridges. In an effort to provide as much internal room as possible, steel is utilized to manufacture traditional 6.8x43mm magazines. A polymer magazine like Magpul’s famed P-Mag is not possible: there’s not enough space.

For commercial sales, the ability to fit a 6.8x43mm magazine into any existing AR lower receiver is a huge selling point. It works, but it’s not an ideal solution. I should note the 6.5x38mm Grendel suffers from a similar issue.

The optimum solution would be to cast aside the standard 5.56x45mm AR lower receiver and design a magazine well specifically for the 6.8x43mm cartridge. This is the ideal solution to the problem. I even proposed this idea to Alexander Arms for the 6.5x38mm Grendel.

Unfortunately, no one in the industry wanted to take a step out into the land of proprietary design. No one except LWRCI, that is. “We worked with a number of manufacturers on improving their existing magazines and then decided to optimize the basic design for the cartridge ourselves,” Mellors said, handing me a magazine.

Make no mistake, developing a proprietary lower receiver is a huge step for a manufacturer to take. When you make something proprietary, you suddenly become the sole supplier and the market may or may not gravitate towards it. So it’s a gamble for LWRCI, but one they think is the right decision for this particular cartridge.

So LWRCI cast aside the existing AR-15 magazine well dimensions and set out to build a complete rifle specifically around the 6.8x43mm cartridge. Initially they designed and produced prototype magazines in-house. But eventually they decided to take advantage of the expertise offered by Magpul Industries.

“It didn’t make sense for us to try to solve problems Magpul had already overcome,” Mellors commented as I examined early prototype magazines. “So we teamed with the folks at Magpul to build a reliable polymer 6.8x43mm magazine. While it would be similar to their famous P-Mag, we did require some changes. First off, it had to look different, so a 5.56x45mm P-Mag couldn’t be confused with a 6.8x43mm magazine. Taking this a step further it also had to feel different, so the two could be distinguished in the dark.

“Plus we wanted the floorplate to be a different design, something slim. We didn’t want it to protrude from the sides of the magazine. This would prevent magazines from catching on each other as they were being withdrawn from a pouch. Plus we wanted a high visibility follower.”

“What we refer to as the ‘Oh Sh!t’ follower,” Gomez interjected with a chuckle. “During the development of the magazine it was important to come up with the correct thickness of polymer for the sidewalls. We wanted it to be very robust. We also asked them to change the gate location on the mold where the plastic is injected. This was done to change where the plastic cooled first. It sounds like a little thing, but little things add up. Basically we added as much room as physically possible to the magazine without having to completely redesign the bolt carrier.

“The new design allows a longer cartridge overall length of 2.32 inches, for future long-range loads, and provides enough room for the cartridges to stack properly. Since the cartridges stack properly, we can have a full 30-round capacity without noticeably extending the length of the magazine compared to a 5.56 piece.”

LWRCI then built a dedicated 6.8x43mm platform to utilize the new magazine design. While it looks identical to a standard AR-15 in size, it is not. Not only is the lower different but so is the upper receiver, to accommodate the wider magazine feed lips. The forged receivers are struck twice, once before and then again after heat treating. This is referred to as coining.

“Basically this process ensures very tight tolerances from receiver to receiver. While it doubles the cost, it is well worth it and provides a very attractive final finish,” Mellors explained.

“I designed the magazine funnel to be as aggressive as possible,” Gomez added, “to speed reloads. Plus I incorporated a magazine stop into the mag well to eliminate the possibility of over-insertion of a magazine. In addition a shelf was incorporated into the rear of the lower receiver by the receiver extension. This was added to mitigate carrier tilt.

“I felt it was important to not only add ambidextrous controls, but to make them truly useful when shooting the rifle either right or left-handed. As an example, when shooting right-handed, a rifleman can easily lock the bolt back or release the bolt from a firing grip. You will also note that unlike many ambidextrous safety designs, the right lever does not interfere with your trigger finger.

“When it came to the charging handle, we tried all the existing ambidextrous ones but eventually I decided to design my own. Basically I designed it like a wine bottle opener with a rack and pinion system. The upper receiver itself needed some tweaks due to the different cartridge. As an example the ejection port was redesigned. It was not only made larger but I also tapered it. Then a compound bevel was added to the case deflector.”

“Why did you modify the case deflector?” I interrupted.

“Using high speed video, we determined the bolt velocity and ejection pattern both suppressed and unsuppressed. Then we specifically optimized the case deflector to provide a consistent 3 to 4 o’clock ejection pattern even when suppressed. Remember this isn’t a 5.56mm gun and we wanted to eliminate the possibility of a fired case being kicked back into the ejection port.”

All of this work has been incorporated into an eye-catching 8.5-inch gun dubbed UCIW SIX8. This Ultra Compact Individual Weapon offers terminal performance and penetration on a level far beyond what traditional PDWs can provide.

It easily kicks dirt in the face of the 5.7x28mm and equally short barrel 5.56x45mm, 5.45x39mm, 5.8x42mm and even 7.62x39mm systems. Developed with Personal Security Details, EOD Technicians, helicopter and vehicle crews in mind, it has a wide range of applications.

To further reduce the size of the system it features a special short receiver extension and utilizes a buffer with two internal tungsten weights. The stock is also reduced in size compared to the norm. With the stock collapsed, overall length is just 24 inches. With the stock extended, this grows to 26.7 inches. Height with a magazine inserted is 10 inches and width is 2.6 inches. Empty with no magazine, it weighs just 6.3 pounds. Loaded it tips the scales at 7.5 pounds.

The 8.5-inch barrel is cold hammer forged from 41V45 steel and treated with a NiCorr finish rather than traditional chrome-lining. LWRCI claims their NiCorr surface conversion is harder wearing, more heat and corrosion resistant than hard chrome plating. They claim the barrels have a service life of approximately 20,000 rounds compared to 6,000 to 10,000 for a standard M4. Barrel twist is 1:10, and it is cut with a SPC II chamber.

LWRCI is known for its patented self-regulating short-stroke gas-piston operating system. As you’d expect, this is utilized on the UCIW SIX8. One of its benefits is it eliminates the venting of hot, carbon-laden gases into the receiver and bolt carrier assembly. This not only eliminates fouling being injected into the action, but also the heat from the gases utilized to operate a traditional Stoner system.

Bolt carrier assemblies feature a proprietary nickel coating to eliminate corrosion and increase lubricity. Surrounding the piston system is a free-floating fore-end with Mil Std 1913 rails at 12, 3, 6 and 9 o’clock. This allows mission essential accessories to be easily mounted. An easily removable top rail section provides ready access to the piston system. A set of folding back-up iron sights complete the carbine.

LWRCI didn’t stop with just designing a dedicated rifle and magazine for the 6.8x43mm cartridge. They took it one step further by teaming with ATK to develop ammunition. Why ATK? Unlike many of the smaller ammunition manufacturers out there ATK is a giant with incredible resources at its disposal. Their design and engineering departments are impressive with state of the art equipment and their manufacturing capabilities vast.

ATK currently manages the government-owned Lake City Army Ammunition Plant in Missouri. This 3,900+ acre facility is the largest ammunition plant in the world. Its primary customer is the U.S. Army.

To meet the needs of one large foreign contract, LWRCI worked with ATK to develop a load specifically designed for the 8.5-inch UCIW SIX8. The starting point for this project was to design and build a suitable cartridge case. Current commercial 6.8x43mm SPC cartridge cases vary in both case capacity and web thickness. LWRCI wanted a case with a strong web for durability. So ATK produced a case with a thick web suitable for military use.

To increase muzzle velocity from the very short barrel, LWRCI specified a 90-grain bullet. It would reduce felt recoil while making the UICW SIX8 more controllable, especially in the full automatic mode. Yet this bullet weight would still retain enough energy to penetrate intermediate barriers well. Practical range would be 300+ yards, even from the stubby barrel. Three loads were initially proposed for testing. These consisted of a 90-grain Gold Dot, 90-grain Monolithic HP and a 90-grain FMJ.

Next, a wide variety of powders were tested to obtain the highest muzzle velocity possible while still providing a measure of safety. Heat stability of the powders was also extremely important, so testing was conducted from -29.2 degrees to 125.6 degrees F. The top performing powder was then selected and loaded to provide pressures within the SAAMI specifications.

Why is this important? Experience has shown that if stable powders are not utilized, pressures can spike when ammunition is stored in a very hot environment. I can say from personal experience the inside of a vehicle can reach 140 degrees in the summer heat of the Middle East. ATK also optimized this propellant to reduce both the flash signature and muzzle blast.

The primer was designed to meet U.S. government primer sensitivity specifications. This was then loaded with the same primer mixture as utilized on ATK’s Federal Gold Medal Match ammunition. Both the primer annulus and case mouth are sealed and crimped per U.S. military specifications. Plus the annealing of the case is not polished off as is common on commercial brass.

Projectiles were then tested to choose the most suitable design for this application. Projectiles were tested using 10-percent ordnance gelatin. This was done using bare gelatin and commonly encountered intermediate barriers placed in front of the gel blocks.

Testing eventually led to the 90-grain Gold Dot being selected. This features a .035-inch jacket and a bonded core. Average muzzle velocity for this load from the 8.5-inch barrel measured a respectable 2450 fps. In doing so, this load generates 1199 foot-pounds of energy at the muzzle. Firing the same load from a 16-inch barrel produces 2900 fps and 1680 foot-pounds.

Taking barrel length to 24 inches increased velocity to 3050 fps and energy to 1858 foot-pounds. Testing in extreme temperatures showed velocity to average 2275 fps at -29 degrees F and 2475 fps at 125 degrees F from the 8.5-inch barrel. When fired from a 24-inch test barrel, ATK recorded a group measuring 1.56 inches at 200 yards.

The end result of all this work is a highly effective load optimized for LWRCI’s 8.5-inch UCIW. Interested to see how it would perform, photographer Richard King and I were afforded an opportunity to spend an afternoon on the range with an 8.5-inch UCIW and a 16-inch carbine. King is an LE officer with SWAT and K-9 experience as well as being a competitive shooter. So we took turns running both systems on steel and comparing notes.

We both found the ambidextrous controls eminently usable, well placed and easy to operate. Rounds loaded smoothly from the magazines and fed flawlessly.

Practical accuracy was excellent, and the stubby 8.5 inch gun proved very easy to hit with. Shot-to-shot recovery was very good for the 8.5-inch gun and excellent for the full-size 16-inch gun. Using ATK’s 90-grain load made the 16-inch gun very smooth-shooting. No malfunctions or problems of any kind were experienced, even during multiple full-auto magazine dumps. LWRCI’s carbines, Magpul’s magazines and ATK’s ammunition all performed without any issues.

My thoughts? I am impressed by LWRCI’s work on building a dedicated 6.8x43mm AR. It appears very well thought-out and is intended to cast off the shackles of the existing 5.56x45mm design. All this work will pay dividends for the commercial customer as well. LWRCI will be offering SIX8-based platforms commercially.

ATK is bringing out commercial 6.8x43mm ammunition in their Fusion and American Eagle lines. The 6.8x43mm SPC cartridge has come a long way since it was first introduced in 2004. It will be interesting to see what the future holds for it next.


The 6.8x43mm Rem SPC cartridge outperforms the 5.7x28mm, 5.56x45mm, 5.8x42mm, 5.45x39mm and even the 7.62x39mm when fired from short barrels.

Photos by Richard King

  • 7SFCW4

    After humping a .223 with the US Army for twenty-two years, I swore I'd never on an AR/M-16, the 6.8SPC changed my mind. IMHO the US Military would be wise to adopt the 6.8, true wisdom is hard to find. Maybe if the draft was re-enstated?

  • Croge

    Very cool indeed, will be interesting to see if other uppers might come along. Would love to see a mid weight 18" 6.5 Grendel rig. a 5.56 would also be of some use to extend the usefulness of the lower to other ammo more findable in many places. The ATK stuff will most likely be really hard to find for us common folk and, I suspect, really pricey!

    As a LWRC owner I have great respect for their gear and was about to pull the trigger on a 6.5 from elsewhere but will wait some to see if there is a chance it might be done right by LWRC. I'd buy one in a heart beat!

  • chuck

    LWRCI makes amazing weapons! I own two! The weapons are pretty pricey but I would rather wait a little bit and purchase a superior gun!

    There is No reference to price here which is always a consideration for most civilians. Please tell me what the different versions will cost,when the weapons will be available and how hard it will be to get Ammo.

    With only one supplier ammunition can be a huge problem. How much will the "new" rounds cost?

  • John

    Is it correct that it gains 60 fps from an 8.5 to a 16-inch barrel and then only 18.75 fps from a 16 to a 24-inch barrel? Any thoughts on why that is?

    • Patrick

      No this is not correct. I beleive they got 2450fps from an 8.5" barrel. You will get 2900fps from a 16" barrel. The difference between 16-18" will se an increase of 50fps (average) for a rough grand total of 2950fps

      • John

        Patrick, I'm just doing the math. 16 – 8.5 = 7.5 inches of barrel. 2900 – 2450 = 450. 450 divided by 7.5 = 60 fps increase per inch from an 8.5 to a 16-inch bbl. The 24 bbl got 3050. 3050 – 2900 = 150, which, divided by 8 inches equals a gain of 18.75 fps from a 16 to a 24. Right? But why?

        • Patrick

          Misunderstood you. Sorry. I thought you meant the total difference between an 8.5" barrel and 16" barrel was 60fps. Your numbers are correct. The reason why you get such diminished returns past 16" is because of the faster more efficient powders used with the 6.8. It is optimized for 16" barrels so you get little gain by going longer. General rule of thumb with 6.8 is you gain on average 25fps for every inch past 16".

          • Patrick

            They got an average of 18.75fps more going to 24 inches like you say. Once you get past 20" the returns really drop which probably affected the average. With the 6.8 an 18" barrel is really the maximum. There is just no reason to go longer, which is just my opinion. Others may disagree.

  • Double Diamond

    What is wrong with this picture? A weapon that will cost $2500 + and a buck + a round Hmmmm I wonder why the best intermediate cartridge is so expensive. Why is it that .300 Blk ammo is cheaper. I can buy .308 for less and have twice the energy. For me to part with that kind of bucks I can buy an AP4, a suppressor and a ton of ammo…I would love a cool SBR with the LWRC stamp but seriously can't or won't part with it… For close in work I'll take my chances on an AK-47 SBR. 7.62 x 39 has been getting it done for awhile. I invite any and all ammo manufacturers to bring 6.8 in line with current pricing. That would go a long way to me purchasing a new gun…

  • Darren@lwrci

    Expected MSRP on ammunition is about .50 cents.

  • Ktn

    did you save any brass and could I buy some once fired?

  • Patrick Hernandez

    What does this mean for us current LWRC 6.8SPC owners? Will our rifles not accomodate the current 6.8 round anymore?

  • Steve Ragan

    .50 a round? Really?

    I currently own an 8.5" 6.8 (non LWRC), and that sounds like an outstanding round. I've avg'd 2550 with SSA/Barnes 85gr tac loads, and 2689 with standard load (??). The 90gr sounds like a great performer at an outstanding price.

    Any idea on when this round will be available?

  • @Lakan_Kildap

    according to LWRCI catalog this was developed for the British for use in vehicles and other confined spaces. The SAS, the granddaddy of all modern special forces, have been early adopters of the AR platform (US AR, then Canadian AR, then HK-416), and this means they're still believers. Not sure if the British have actually adopted the UCIW, though. But LWRCI's efforts in making the AR more reliable, including the Individual Carbine, are laudable.

    Colt has a similar shortened buffer/stock weapon (named SCW – sub compact weapon), but with a stock that both telescopes and folds.

    LWRCI's gas piston system is nice, but it's hardly new. The Armalite AR-18 used a similar arrangement: cup-type piston, segmented rod.

    • John

      These new SIX8 rifles and Federal ammo are going to the royal guards of Jordan and Saudi Arabia.

  • themadscientist

    I'm happy with my current 6.8 LWRC with the longer Barrett mags. I am glad they are advancing the platform, but I have no need of this newer rifle. looking forward to getting a 300 AAC buddy for him though.

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