If you are looking for a more potent alternative to the 5.56 NATO for an AR-15 rifle, you will encounter lots of options, but for universal use, the best cartridge is the 6.8 Remington SPC (6.8x43mm), especially when used in shorter barrels.
Unlike the 6.8 SPC round, purpose-built from the very beginning for optimal performance in the shorter barrels, the .223 Remington/5.56NATO round was designed for 20-inch barrels that are not quite as popular for close quarter fighting.
In other words, firing 6.8mm ammo will give better performance from the ubiquitous SBR than the 5.56mm can give you from the shorter barrel.
Best 6.8 SPC Barrels Comparison Chart
AR-15 Recon Barrel 6.8 SPC II
AR-15 Ranger Barrel 6.8 SPC II
6.8 SPC II Barrel 20 in Stainless Steel
Wilson Combat Match Grade Barrel 6.8 II SPC Fluted 16" 1-11 Twist Stainless WC
What is the Optimal Barrel Length for the 6.8 SPC?
Developed in response to objections about the stopping power of the 5.56 mm ammo, the 6.8 SPC ammunition aimed to improve on 5.56mm NATO cartridge lethality from the M4 carbine (16-inch barrel). By the book, the 6.8mm Remington SPC was conceived for 12" to 16" barrels, currently most familiar in a short-barreled rifle (SBR)/carbine platforms.
The 6.8 SPC is capable of pushing .277 caliber, 110gr bullets from 16" barrel easily up to 2,500 ft/s, significantly improving terminal ballistics over a 5.56x45mm NATO 77gr with MV of 2,679 ft/s.
Furthermore, the 5.56 ballistic performance in the AR-15 platform will decrease when you start chopping down the barrel length. The 6.8 SPC ammo does quite well from shorter barrels since it was specifically designed for efficiency in a short-barreled rifle (SBR).
While the performance of the 6.8 SPC out of a 16" barrel is arguably second to none in an AR pattern service rifle, it gains minimum velocity as barrel length is increased.
As a final verdict, by increasing barrel length beyond 16 inches, you might get a bit of extra power from a longer barrel, but it would be not enough for most applications to be worth the hassle.
Perks of Upgrading Your 6.8 SPC Barrel
As mentioned earlier, the barrel length in the 6.8 SPC caliber may have a slight influence on the ballistics performance and hence, on your shooting style, but the "optimum barrel length" really depends upon your intended use.
In fact, testing has found that the velocity benefit you can gain is about 30fps per inch from 16" to 20" barrel lengths, depending on loads. So, a 20" barrel will provide long-range precision, boasting slightly higher velocities and slightly less bullet drop.
At the other end of the spectrum, using a 6.8 SPC in a 12.5" SBR or shorter AR pistol configuration is the perfect solution for vehicle and home defense.
However, the most popular is the 16" carbine which provides you about 85%-90% of the 6.8 cartridge's maximum velocity. Besides, this is the shortest length legally allowed in most states. It is also a handy size but still shoots great in groups, making it an ideal weapon for carrying on-foot, during the day, or nighttime hog hunts up to about 200 yards.
Features to Consider When Buying a New 6.8 SPC Barrel
The quality of the barrel is the crown jewel of any AR-project and before you start investing in barrels to expand your shooting capabilities, you should consider a couple of features that would determine the future use of your 6.8 rifle.
First, you should look for a 6.8 SPC II chamber, as this is the corrected version of the original 6.8, chambering with better performance and readily available for purchase from the large majority of barrel manufactures.
Generally, the 6.8 SPC is a multi-purpose rifle but when building the 6.8 upper for specific tasks, you should know that you cannot assemble a great shooting AR rifle/carbine without a great barrel.
The evolution of the AR-15/M16 barrel ranges from the original lightweight 20” rifle barrel all the way up to the most popular barrel profile today known as the 14.5″ military M4 barrel.
While the original pencil-style, or “A1”, barrels were good for snapping off single shots, they were not as good for full-auto shooting. Therefore, development moved toward heavier profiles, so there were new barrels designed called the Special Purpose Rifle (SPR) and Designated Marksman Rifle (DMR) barrels with a length of 18 and 20 inches respectively. These barrels are not designed for the shooting type known as “spray and pray” but rather for slow, precise, and methodical shooting.
However, one particularly popular profile for the rifles which features a 6.8 SPC II chamber is stainless, 16″ long barrel often called "Recce" or "Recon". These barrels are more massive under the front guard providing useful thermal mass to absorb a lot of shooting.
There are also other profiles available in AR barrels but there’s another way to get lighter weight and that is vertical cannelure, or fluting. In this process, gun makers remove material from the barrel’s outer surface in grooves that run lengthwise along part of the barrel. Next, is a "dimpling" process with a lot of dimples along the barrel's surface. While the fluting makes barrels lighter, both processes produce better thermal efficiency in shedding heat.
While the original 5.56 AR-15s have barrels with 1:14 twist, the current M4 carbines come with a twist rate of one turn per seven inches. Since the 6.8 SPC II rifles prefer bullets weighing between 90 and 110 grains, you should stay away from barrels with a 9.5 twist, in favor of using a 1:11 twist as often as possible.
Beyond these considerations, you should also pay attention to muzzle threads. Some gun authors advocate the avoidance of barrels with a 1/2-28 muzzle thread on a 6.8 since the attested and proven muzzle thread for this caliber is 5/8x24 threads per inch.
Review of the Best 6.8 SPC Barrels
We have picked some of the best barrels for 6.8 SPC in the market and weighed their pros & cons in detail for you to choose the one which suits your needs and taste.
Wilson Combat is a household name in the AR-15 aftermarket industry and their stainless steel fluted 16” match-grade Recon Tactical barrel can handle a range of tasks, from plinking and all-purpose field applications to hardcore hunting.
This Wilson barrel comes with a “Recon” fluted profile that enhances rigidity while remaining lightweight. As an added benefit, the fluting is also designed to provide greater cooling for long strings of fire.
The Wilson Combat 6.8 Recon 16-inch, medium contour, match-grade barrel is machined with a mid-length gas system and hand polished M4-style feed ramps and passed the complete and rigorous final inspection process.
These proven 6.8 SPC II barrels feature a precision muzzle crown with 5/8" x 24 muzzle threads and crisp CNC markings.
For gilt-edge accuracy, each Wilson Combat AR-15 Recon barrel offers a four-groove precision button rifling with a 1:11" twist rate for excellent performance with bullet weights from 85 to 115 grains.
Combining a match-grade barrel that is four inches shorter than the M16A4 main battle rifle and 416R stainless steel, the Wilson 6.8 Spec II Chambered Recon Barrel is perfect for any build requiring reduced mass and increased durability.
The venerable Wilson Combat has released an AR rifle series dubbed the Ranger, designed as a reliable, easy-to-carry hunting rifle where lightweight is a prerequisite. For the AR-15 series, Wilson Combat has developed a Ranger match-grade, tapered barrel available in 14.7″ or 16-inch lengths, depending on the caliber.
If you are building a fast-handling, precision AR carbine, then you should consider the Wilson Combat Ranger profile barrels as the lightest contour of Wilson AR barrels.
The company’s model TR68RAMG16RT11 in 6.8 SPC II chamber is available with a 16″ barrel and weighs less than 27 ounces, making it one of the lightest barrels on the market.
The barrel is machined of Type 416R stainless steel for longevity and comes with a mid-length gas system and a standard .750-inch gas-block journal. The Ranger barrel also sports M4-style feed ramps while the barrel top features 5/8x 24 threaded muzzles.
For exceptional accuracy with standard bullet weights between 90 and 110 grains, the new Wilson Combat AR-15 Ranger barrel combines six groove button-rifling with a right hand 1:11" twist rate. Actually, this match-grade barrel offers extraordinary accuracy for such a light profile and out-shoots average shooting mechanics as it keeps sub 1/2 MOA groups at 100yds.
Although the Wilson Combat barrels are made to mil-spec standards, there are rare complaints on final quality control concerning incorrectly cut chambers.
The Wilson Combat Ranger barrel is ideal for upgrading an existing AR-15 to cut down the weight of their black rifle without any accuracy loss.
In addition to making a rifle easier to carry for long periods of time, the 16″ Ranger barrel increases speed when transitioning between targets.
Columbia River Arms has recently acquired Black Hole Weaponry, but they continue to make custom rifle barrels using state-of-the-art technology. If you want substantial accuracy improvements in AR platforms, then the BHW/CRA barrels are an excellent value for upgrading your standard AR's accuracy.
Black Hole Weaponry barrels employ the use of match-grade 416R stainless steel with a Rockwell 27 and utilize polygonal twist rifling typically found in Glock and H&K firearms.
Unlike the traditional sharp-edged lands and grooves, this arc-shaped rifling offers gentle hill and valley forms to add accuracy, reduced gas cutting, increased velocity, and ease of cleaning.
This BHW 20-inch barrel features Caudle 3 land polygonal rifling, 1:11 twist rifling, and 6.8 SPC II chamberings. Unlike general five-groove rifling, three-groove polygonal rifling is more of a match style of rifling for longer barrel precision weapons where accuracy is a must.
The Black Hole Weaponry barrel with code AR15-6.8SPC-1x11-20-CON is highly configurable in terms of several custom fluting options and contours. This particular 20-inch HBAR barrel comes with the recommended rifle-length gas system, Bull profile, and straight fluting. Paired with 5/8" x 24 muzzle threads, this setup provides heavy barrel accuracy with good heat management.
All Black Hole Weaponry custom rifle barrels have passed the magnetic particle inspections (MPI) and further non-destructive testing to ensure the integrity of each barrel. Though sometimes you will not get complete instructions, as a standard procedure, you need to fire about 50 rounds to break in the barrel properly.
If you are looking for sub-MOA accuracy and are focused on building high-end Black rifles, Black Hole Weaponry has match-grade polygonal rifled barrel upgrades capable of holding accuracy during sustained fire.
Wilson Combat manufactures over 40 different variations of barrels in six popular chamberings.
Nevertheless, if you wish to build your own general-purpose rifle well-equipped for hunting, home defense, or tactical competition, Wilson Combat is offering their Recon Tactical profile 14.7" barrel. With the Recon configuration, your 6.8 SPC AR swings easily and quickly during tactical shooting, without sacrificing any accuracy.
This medium-weight, 14.7-inch match-grade barrel is crafted from 416R rifle rated stainless steel making it ideal for a high rate of fire. While the 14.7 Tactical-Recon 6.8 SPC barrel features hand polished bore and M4-style feed ramps, its machining and precision button rifling is absolutely flawless providing superb accuracy with .5-inch groups being common.
The SR stands for "Suppressor Ready" meaning the muzzle features 5/8×24-TPI threading, which optimizes the build of your AR platform so it can accept sound suppressors. Besides the "Suppressor Ready” feature for secure flash hider/suppressor attachment pinning, the Wilson Combat 6.8 SPC 14.7" SR barrels are also great for non-suppressed application. To avoid the short barreled rifle (SBR) configuration subject to NFA rules and to stay away from registering the carbine as an NFA weapon, your barrel should meet the 16” minimum barrel length requirement for legal rifle ownership.
In that case, you do need to permanently attach a muzzle brake/flash hider of sufficient length to bring the barrel up to 16".
Other Recon barrel features include a matte bead blast finish with a 1:11” twist rate and mid-length gas system.
If you want precision accuracy in a small package, you should consider Wilson Recon SR 14.7” barrel for your next custom AR rifle project.
Installation of the Recon SR 14.7” in your build rifle is great for CQB circumstances but also with a permanently attached flash hider or muzzle brake it maintains a handy, optimized size and weight profile without sacrificing any reliability.
Today, when many AR aficionados are building a number of different tasks focused on high-end ARs, the heart of every project would be a match-grade barrel, which can net the most significant benefits.
Regardless of whether you are planning to use your 6.8 SPC chambered AR-15 as a practical, all-around AR set up or as Designated Marksman Rifle (DMR), all of these missions demand a compromise between handling and weight for carrying, as well as muzzle velocity and heat absorption for optimum accuracy.