Review: LWRC SIX8-SPR Carbine

posted on December 13, 2017
While the 6.8 SPC cartridge has been around for more than a decade, most rifles chambered for it were AR-15s reconfigured to handle the 6.8x43 mm round. In 2012, however, LWRC International of Cambridge, MD, took the bull by the horns and designed a new platform around the cartridge. Called the Ultra Compact Individual Weapon (UCIW), the new rifle was in reality an ultrashort-barreled, selective-fire carbine. With an 8.5-inch barrel, the UCIW incorporated all of the patented features of LWRC’s superb 5.56 NATO rifles, and then some. Many key parts were also incredibly short, including the piston group and recoil-spring group.


Just as interesting is the commercially available, 16-inch-barreled LWRC SIX8-SPR Carbine. This new carbine incorporates all of the company’s patented features and more. Most of the innovation is in the rifle’s guts—the short-stroke piston uses a piston cup, an intermediate rod and an operating rod to engage the bolt carrier. In place of a gas key, the one-piece carrier has what LWRC calls a “tombstone,” which in turn is struck by the operating rod. The face of the tombstone is concave to mate with the tip of the convex op-rod, ensuring it retains the exact position in cycling. Meanwhile, the piston system has its own return spring and moves only about a quarter inch to operate the bolt group. Integral to the rear of the carrier is an enlarged “boss” with drainage slots, which greatly reduces the “carrier tilt” seen in other piston-operated systems.

With a nickel-boron finish, generous relief cuts and a dual-spring extractor, the bolt-carrier group helped the SIX8-SPR achieve excellent accuracy and reliability marks from the author.

Double striking (“coining”) the receivers greatly strengthens the 7075-T6 aluminum alloy. In keeping with strong receivers, the LWRC SIX8-SPR Carbine has a cold-hammer-forged, 41V45 steel barrel with a NiCorr finish, promising a lifespan of 20,000 rounds. The specially designed bolt carrier has generous relief cuts in its rails to trap debris, and is treated with an extremely lubricious, proprietary nickel finish. Using the same finish, the bolt also houses a dual-spring extractor for maximum reliability.

Most shooters will welcome the slim-line, free-float 7075-T6 handguard, the lower section of which is attached to an upper-receiver extension. Requiring only two retaining screws to be loosened by hand, the upper section is simply moved forward to unlock, and then lifted off to access the op-rod for easy removal.

Two furnished alloy rail panels and a front sling mount can be attached to suit the user. Also standard is a Magpul pistol grip and a well-designed, six-position proprietary buttstock adjustable for length of pull.

The front sight is shrouded for protection, and the rear sight is a peep-style adjustable for elevation and windage. Both sights mount on the top rail of the SIX8-SPR.

The open “Skirmish” sights on the LWRC SIX8-SPR Carbine are rugged and refreshingly easy to use thanks to a ghost-ring rear aperture. Meanwhile, the upper receiver, while identical in length to that of a standard AR, has an enlarged ejection port and internal modifications to accommodate the feed lips of the new 6.8 Rem. SPC magazine, made by Magpul.

The lower receiver’s most obvious departure from the norm is a totally redesigned magazine well that is both longer front-to-back and wider than that found on a 5.56 NATO carbine. A 5.56 NATO magazine will not lock in it—another indication the LWRC SIX8-SPR Carbine is a 6.8 Rem. SPC gun from the ground up.

Also found on the lower receiver are LWRC’s well-designed ambidextrous controls. Eugene Stoner’s AR platform was designed to preclude the need to remove the hand from the fire control group, except for manually locking the bolt to the rear. The LWRC SIX8-SPR Carbine’s ambidextrous bolt-release tab makes it a cinch for the right index finger to operate when pulling the charging handle back with the left hand.

To access the operating components for cleaning, all one needs to do is hand-loosen two bolts at the front of the handguard. The top of the fore-end can then be lifted off.

Disassembly is as with any AR type rifle, save for partially unscrewing two retaining bolts at the front of the upper handguard to slide it forward, up and off to access the piston group. With the bolt to the rear, the piston is simply pulled rearward to remove it and the operating-rod parts.

I had the opportunity to test the LWRC SIX8-SPR Carbine using Speer’s 6.8 SPC ammunition. Designated XM68GD, it was designed for a special customer and the load has only been on the shelves for a couple years. LWRC was able to furnish me with a test quantity of this ammunition. I also had on hand 6.8 Rem. SPC offerings from RemingtonHornady and Nosler.

Using Aimpoint, EOTech and Trijicon ACOG optics, offhand hits were easy on steel targets out to 200 yards, and a simple rest extended the quick-hit range to 400 yards on known-distance targets. Overall, accuracy from the LWRC SIX8-SPR Carbine was very good, no malfunctions occurred and all operations of the rifle were performed smoothly.

undefinedThe trigger is fairly typical for an AR with a pull weight slightly heavier than 5 pounds, but there was a good deal of creep, which affected accuracy. Triggers can be a matter of choice, and the user may opt to replace the stock trigger with a match-grade unit from one of the many aftermarket options. While LWRC’s Skirmish sights and buttstock can also easily be replaced, I found them much to my liking.

The LWRC SIX8-SPR Carbine and UCIW platform amount to a big surprise, and an exceptionally well thought out, giant step in the AR market. After a decade-long wait, the 6.8 Rem. SPC train finally left the station on a fast track with the SIX8-SPR.


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