Challenging The 5.56 NATO: The LWRCI 6.8 SPCII

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LWRCI Six8 side view

A culmination of a slew of incremental changes, the LWRCI Six8 aims to tackle the 5.56 AR's supremacy.

What The LWRCI Six8 Stands Out :

  • The barrel is 8.5 inches long, NiCorr treated and has a twist of 1:10 inches.
  • Barrel is heavy profile, which keeps it a bit nose-heavy (I find this good for follow-through and tracking a moving target) and soaks up heat.
  • With a threaded muzzle and adjustable piston system, the pistol can easily accommodate a suppressor.
  • Lower handguard bolts directly to the upper receiver, leaving the barrel nut to do its job without being imposed upon.
  • A standard bolt has been built it for the 6.8.
  • Six8 magazine is wider than a USGI 5.56 magazine to properly stack the fatter 6.8 cases.

The LWRCI Six8 is the culmination of many incremental changes. It’s fashionable to be “revolutionary” or “boundary-pushing” these days. Well, real progress is made with incremental changes that add up to something that’s far beyond the original. The Six8 is what the AR would have been if the powers-that-be hadn’t been so invested in NIH — Not Invented Here.

There has always been a cohort of shooters who have not been happy with the AR-15. Some didn’t like the gas system. Others found the aluminum and plastic construction just not “manly” (not enough steel and no walnut).

LWRCI Six8 Dust Cover
From the right side, there’s only one clue the LWRCI is ambidextrous: the bolt release, which is located above and behind the magazine button.

And others objected to the 5.56 NATO cartridge. As a CQB and jungle cartridge, it actually worked then, and it works now, at least in the full-sized rifle. Push the 55-grain FMJs out of a carbine or an SBR, and the distance at which it works closes in sharply.

How It Works

Briefly, the 55 FMJ works through yaw and fragmentation. When it loses enough velocity, it fails to fragment. Out of a rifle, the 55-grain FMJ bullet — the load commonly known as M-193 or XM-193 — fragments out to 200 yards or so. But as you shorten the barrel, you lose velocity, and that pulls in the fragmentation distance. By the time you get down to the SBRs, the pistols — the real shorties —you can have a firearm with a zero frag distance. No, really, an AR pistol with a 7-inch barrel has lost so much velocity that the bullet will not yaw and fragment at any distance.

What to do? Well, the Army had a chance some years ago and passed on it. The project was spearheaded by service personnel in the know and was pushed by the SF community. It was called the 6.8 SPC … actually, the 6.8 Remington SPC, to be complete.

The problem with the 5.56 was, well, being 5.56mm. To get more weight, you needed to increase diameter. But the .223 case was too small to get heavier bullets up to useful velocities.

LWRCI Six8 Magazine
The Magpul-made magazine is not only 6.8 specific, it is also LWRCI specific.

So, Remington took the old .30 Remington case, developed back before World War I, shortened it, necked it down to accept a .277-diameter bullet and made the package fit an AR-15 magazine. The result was a cartridge that could push a 115-grain bullet to almost 2,600 fps out of a rifle.

The advantages were seen as many: It fit into the AR. It needed only a new bolt and a new barrel to swap rifles and carbines. It even used the same magazines.

Pros and Cons

However, there were problems. Oh, the big problem was that Army ordnance wasn’t interested in anything that wouldn’t culminate in a multi-billion-dollar project. The Army had to have something that was so great a leap over the existing system that it would be hailed as a genius for having developed it. (OK, I’ll lay off the coffee and get back to our LWRCI Six8 now.)

The mechanical problems with the 6.8 SPC come down to two things: the bolt and the magazine. By simply opening up the existing bolt face, it’s easy to accommodate the 6.8 in an AR package. But the bolt for the AR was designed and proportioned for the 5.56. Asking it to handle a bigger cartridge that’s firing a heavier bullet is asking a lot.

LWRCI Six8 Controls
On the left side of the lower receiver, you can see all the ambidextrous goodness the LWRCI Six8-A5 has.

The idea of not having to change magazines was also appealing. However, the magazine for the AR, like the bolt, was designed for a smaller cartridge. Does the 6.8 work out of AR mags? Yes and no. I have a sample of 6.8 rifles, all rebuilt from 5.56. One of them was a real pain in the neck. It refused to feed reliably until I had sorted out the magazines it likes. I have them labeled, and I keep them with it, because if I use other mags it refuses to work reliably. This became so apparent so quickly that magazine makers altered AR mags to be 6.8-specific and offered them as such.


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This actually makes the problem worse. We now find ourselves with two sets of magazines, and both fit both rifles. Both hold both cartridges, and yet, each will fail to feed if used in the wrong rifle-magazine-ammunition combination.

LWRCI to the Rescue

So LWRCI set about solving this problem. Oh, and they solved another one along the way.

There are actually two 6.8 SPC chambers. One is the original, and the other is the 6.8 SPC II. The difference is the length of the leade; yes, this’s exactly the same situation as we find in the .223 versus 5.56 chamber dimensions. You want a 6.8 SPC II chamber in your 6.8.

LWRCI Six8 Rear Sight
The LWRCI Skirmish
sights fold, and the rear rotates to give you a small or larger aperture.

The subject of our inquiry is the LWRCI Six8 pistol. The model sent to me was the Six8-A5, done up in OD Green. You can have yours in OD Green, Patriot Brown, Flat Dark Earth or black. The colors are Cerakote, applied in-house by LWRCI. The black is mil-spec anodizing.

The barrel is 8.5 inches long, NiCorr treated and has a twist of 1:10 inches. NiCorr is a nitride surface treatment, done to the LWRCI cold hammer-forged barrel. It increases surface hardness to a marked degree and also increases corrosion resistance. As a result, there’s no need for a hard chrome plating in the bore. The 1:10 twist is plenty fast enough to stabilize any bullet you’re going to be using in the 6.8.

The barrel is given a heavy profile, which keeps it a bit nose-heavy (I find this good for follow-through and tracking a moving target) and soaks up heat. Despite the barrel diameter, the Six8-A5 pistol only tips the scales at 6¼ pounds. The muzzle is threaded 5/8×24, so you can mount a muzzle device other than the flash hider LWRCI ships it with. The piston system is adjustable, so it can easily accommodate a suppressor. At the other end, LWRCI reams the Six8 to the 6.8 SPC II chamber dimensions.

Above the barrel is the LWRCI piston system. This is a spring assembly, rod and cup, and they can be removed (but not without a bit of a struggle) for cleaning. The piston system removes the big objection some have with the direct-impingement design, because with a piston, none of the hot gases are directed back into the upper receiver.

LWRCI Six8 Sight
The LWRCI Skirmish
front sight.

The free-float handguard has a removable top. By unscrewing the knobs on the front of the handguard, you can slide the upper portion a bit and then lift it off. Doing this gains you access to the piston system, should you ever want to disassemble and clean it. I’ve been running a couple of other LWRCI carbines for some time now, and I have managed to resist the temptation to clean the piston system. Even so, they have yet to fail me.

Instead of clamping the handguards onto a mil-spec barrel nut or a proprietary one, the front of the upper receiver is altered to be the base of the lower handguard. The handguard bolts directly to the upper receiver, leaving the barrel nut to do its job without being imposed upon.

6.8 Table 1

The upper handguard is also railed its full length and meshes perfectly with the rail of the upper receiver. LWRCI installs its own Skirmish sights, folding BUIS front and rear, so you’re ready to go right out of the box.

To complete the ensemble of the upper assembly, LWRCI uses an ambidextrous charging handle. The lower is full ambidextrous, with mag catch, bolt release and selector working on both sides.

LWRCI Six8 Piston Installed
Here, you see the top of the
handguard off, ready for piston disassembly.

The receiver extension, aka “buffer tube,” is a simple tube with a raised collar to stop the arm brace from moving forward. Clamped between the rear of the receiver and the castle nut, LWRCI has positioned a QD sling swivel attachment point. Again, it’s ambidextrous.

Noteworthy Alterations

The two big changes that LWRCI has made in order to make the Six8 work the way the original project was intended to are not readily apparent.

First up: the bolt. LWRCI took the standard bolt and built it for the 6.8. It has a fully supported bolt face, the extractor has dual springs to power it, and the extractor claw has been improved to gain 20 percent more purchase on the rim. The company machined a recess around the rim of the bolt face to collect debris and to keep it from causing problems before you can scrub it away.

The bolt and carrier are nickel-boron coated for increased lubricity, ease of cleaning and easy identification. All these steps improve function, durability and service life of the bolt.
The other big change is the magazine. LWRCI collaborated with Magpul, and they made sure the new cartridge got a proper magazine.

LWRCI Six8 Barrel
The barrel is clearly marked, and the
NiCorr treatment makes it harder than sin and tougher
than an auditor’s heart.

The Six8 magazine is wider than a USGI 5.56 magazine to properly stack the fatter 6.8 cases. The magazine has feed lips proportioned to feed the 6.8 out of the proper double-stack configuration. Internally, the Six8 magazine is a continuous-curve shell. The USGI 30 round magazines are a straight upper tube with a curved lower half. The lower receiver is machined to accept this new magazine.

And, as a very clever decision, LWRCI and Magpul moved the magazine catch slot just enough so that a regular AR magazine won’t lock into place in the Six8. As a final touch, the magazine features a bright-red follower so you can tell at a glance which is which.

The resulting package is a compact, relatively lightweight (a comparable AR-15 in 5.56 can be had under 6 pounds, but to do that, you give up the piston system and the heavy barrel) self-loading rifle that holds 30 rounds of 6.8 Remington SPC ammo.

Why Choose the 6.8?

Now, one might ask: Why a 6.8 pistol? Aren’t you giving up the power advantage the 6.8 gives you over the 5.56? You aren’t, and the answer is related to the square-cube law — that is, the size or strength of something goes up by the square, but the mass goes up by the cube.

LWRCI SIX8 Table 2

A 115-grain 6.8 bullet doesn’t have to depend on fragmentation to work. You can count on expansion … if you want expansion. If you’re using FMJs, the mass (the 6.8, at 115 grains, has 209 percent the mass of the 55-grain bullet in an M-193 load) delivers the ballistic punch. If you need barrier performance, a bonded 115-grain 6.8 bullet is going to do much better than any similarly constructed 5.56 bullet. And the chronograph results tell us just what a barrel as stubby as the Six8-A5 can deliver.

One thing to keep in mind if you decide to reload your 6.8 ammo: primers. The original design, done by Remington, called for a large rifle primer. That, like the original short-leade chamber dimension, has been retained by Remington. Hornady loads the SPC with small rifle primers. If you order up new brass from Starline, they, too, will ship you cases with small rifle primer pockets.

As a “truck gun,” the LWRCI Six8-A5 would be a great little emergency tool. You have plenty of oomph to defeat barriers. You have the power to reach out past the immediate vicinity. If you’re out in the country and have need of it, the 6.8 SPCII can easily reach out to a couple of hundred yards. With a low-powered scope on it, that would be even easier.

For more information on the Six8, please visit www.lwrci.com.

Editor's Note: This article originally appeared in the May 2019 issue of Gun Digest the Magazine.


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