Choosing a caliber outside of the infinite, logistically supported 5.56×45 NATO cartridge choice on an AR-15 platform took a leap for me.  Many of the subscribers to The Channel may be familiar with my 25 plus years on the platform and the often touting of mil-spec standards or better, “time proven” and “tested” systems, as well as my overt passion for the AR-15, M4A1, MK18, MK12 and the entire genetic makeup of what has become, “Americas Rifle” – all of whom share the chambering of 5.56 NATO cartridge.
Several years ago, prior to even the madness of 2012, of which every AR-15 enthusiast still suffers from SVSS (Supply Vaporization Shock Syndrome) when supplies of every part, mag and component evaporated due to the political climate – a very close friend and contributor here on The Channel, began touting the 6.8 SPC.  My thoughts initially were, “Meh…Why switch?”  Why support another platform chambered differently?  As I learned important pieces of information such as, the bolt, barrel and magazines were the only critical components requiring a change, I grew more open minded.
This article is not going to be a lesson in the history, minutia and ballistics that surround 6.8 SPC II nor a comparison of the 6.8 SPC II to other fringe cartridge choices available for the AR-15.  Instead, walk with me through the evolution of how several rifles here on the Denny Ducet Channel came to be chambered in 6.8 SPC II and why.
I take credentials seriously.  Ideas, where they are born, who had them, why, for what purpose was a change developed are things I take into consideration – especially when considering a firearm for my own application or employment into the street or wilderness.  The 6.8 SPC was born in the minds of the U.S. Army Marksmanship Unit Special Operations Command.  They know more than me and likely you.  Done.
The round serves as an intermediate cartridge between the 7.62×51 (.308) and 5.56×45 (.223) offering an estimated 44% more energy out at 300 meters than the 5.56 with very similar trajectory while being capable of utilizing the standard 5.56 receivers, fire control groups, buffer tubes, bolt carrier, and gas systems.  This allows for a more powerful cartridge, without having to make the jump into the .308 chassis AR-10 systems, all of which are comprised of proprietary parts while weighing more in both platform and ammunition load out.
When I first witnessed the capabilities, ergonomic benefit, and handiness of the 6.8 SPC (especially compared to my Ruger M77), we were hunting Antelope on the plains of Montana .  The lethal success of this larger caliber on a rugged mammal on the high plains was swift, ethical and humane. Later that season, I watched as the 6.8 SPC was clutched in cold hands, covered in wool mittens and trudging along on high ridge tops searching for Mule Deer all the while comfortably slung by a Vickers sling.
Range outings furthered my curiosity for the 6.8.  Incredibly accurate at distances I considered critical for any weapon of this size and weight, the .277 caliber bullets repeatedly slapped steel out to 500 meters with a resounding impact.  Did you catch that?  .277 is the same diameter as the .270 Win – the rifle I have forever hunted with.  If Jack O’Connor were alive, and owned an AR, I believe he would choose a 6.8 SPC, but I digress.  Back to range outings.  The groups and fast follow up shots as well as 500+ meter hits with a  mere 3x ACOG, proved the capable, potential of this light and wieldy platform.
The encroaching urge to build a fine 6.8 grew as time progressed.  I began to spec out a platform as well as the necessary parts to build a 6.8 SPC loosely based on the fine rifle which I had been initiated on.  The desire to push the 6.8 SPC II to its utmost accuracy appealed to me, causing me to steer from the lighter Noveske barrel (although highly accurate) to the  X-Caliber SPR profile barrel.  The following parts were acquired in order to execute a superb 6.8 SPC SPR setup:

X-Caliber 6.8 SPC II SPR Barrel
PARTS LIST:
X-Caliber SPR Profile 16” Mid-Length 416R Stainless 5R 1/11 Twist 6.8 SPC II Barrel with an X-Calliber Exterminator Brake
VLTOR MUR Upper
Geissele Nitride Gas Block
WMD Nitromet Mid Length Gas tube
BCM Bolt Carrier
BCM Lower
LWRC 6.8 SPC Enhanced Combat Bolt
Geissele MK2 MOD 1 Rail
Geissele SSA Trigger
Geissele Super Precision 30mm SOPMOD Mount
H2 Buffer
Sprinco Blue Spring
B5 Gunfighter Stock
PRI 6.8 Magazine (15Rd)
Vortex Viper PST 2.5-10×32 FFP EBR1 Reticle

Geissele Super Precision 30mm Mount

1st Group 100 meters, winds 5-10, shooter error
Day one at the range was boringly reliable, and superbly accurate as expected (in spite of shooter error, high heat 80+ degrees with winds 5-10mph and a poor rest).  If you watched the quick video on this initial day (link at beginning of paragraph) you will see how with a mere dozen rounds the rifle was zeroed. This was without having the scope bore sighted and shortly after we had a < 1 moa group at 100 meters(109 yds) .
I have stated this following mantra with nearly every build we here at the Channel have put together. “Good parts make good guns, great parts make great guns”. Rifles and their performance such as immediately seen in this rifle – are a testament to using the highest quality, finest manufactured and precision machined components.  The results;  Accuracy, Reliability, Durability.
The build list for this rifle was not haphazardly thrown together.  There was a year of thought, discussions, experiences to weigh, mission purpose designs to consider and input from other members here.  Nor was the decision to go with 6.8 SPC a rash one.  There was a year of time spent on the final execution of a decision to go with this particular caliber over other available choices.
There will soon be a bipod incorporated into this 6.8 SPC, so as to assist in those situations more demanding of a rest.  I am considering the Harris BRM-S for this application.
So far I am very satisfied with the performance of the Hornady Match 110 grain BTHP, and have cleaned out the local Cabela’s of their supply after a recent clearance sale.  The supply of ammunition is in every sporting good store in our region from what I have seen, and the online supply choices seems to grow annually.
Whether the rumors of NATO adoption again circulating (Jordan and Saudi Arabia already have adopted), the viability of the 6.8 SPC and the survivability of a once obscure corner of the AR-15 world is in my opinion, here to stay, and will likely grow exponentially as time goes on.
If you have a desire to hunt larger game with a lightweight AR-15 platform, look no further than the 6.8 SPC II.
Your questions and correspondence is most welcome.  Thank you for stopping by, reading, liking, commenting and supporting the Denny Ducet Channel!

The Latest 6.8 SPC
This article is courtesy of The Loadout Room.